diff --git a/thys/Relational_Disjoint_Set_Forests/Disjoint_Set_Forests.thy b/thys/Relational_Disjoint_Set_Forests/Disjoint_Set_Forests.thy
--- a/thys/Relational_Disjoint_Set_Forests/Disjoint_Set_Forests.thy
+++ b/thys/Relational_Disjoint_Set_Forests/Disjoint_Set_Forests.thy
@@ -1,1904 +1,2426 @@
 (* Title:      Disjoint-Set Forests
    Author:     Walter Guttmann
    Maintainer: Walter Guttmann <walter.guttmann at canterbury.ac.nz>
 *)
 
 theory Disjoint_Set_Forests
 
 imports
   Aggregation_Algebras.Hoare_Logic 
   Stone_Kleene_Relation_Algebras.Kleene_Relation_Algebras
 begin
 
 no_notation
   trancl ("(_\<^sup>+)" [1000] 999)
 
+context kleene_algebra
+begin
+
+lemma star_sup_2:
+  assumes "x * x \<le> x"
+    and "x * y \<le> x"
+  shows "(x \<squnion> y)\<^sup>\<star> = y\<^sup>\<star> * (x \<squnion> 1)"
+proof -
+  have "(x \<squnion> y)\<^sup>\<star> = y\<^sup>\<star> * (x * y\<^sup>\<star>)\<^sup>\<star>"
+    by (simp add: star.circ_decompose_6 star_sup_1)
+  also have "... = y\<^sup>\<star> * x\<^sup>\<star>"
+    using assms(2) dual_order.antisym star.circ_back_loop_prefixpoint star_right_induct_mult by fastforce
+  also have "... = y\<^sup>\<star> * (x \<squnion> 1)"
+    by (simp add: assms(1) sup_commute transitive_star)
+  finally show ?thesis
+    .
+qed
+
+end
+
 context stone_relation_algebra
 begin
 
 text \<open>
 We start with a few basic properties of arcs, points and rectangles.
 
 An arc in a Stone relation algebra corresponds to an atom in a relation algebra and represents a single edge in a graph.
 A point represents a set of nodes.
 A rectangle represents the Cartesian product of two sets of nodes \cite{BerghammerStruth2010}.
 \<close>
 
 lemma points_arc:
   "point x \<Longrightarrow> point y \<Longrightarrow> arc (x * y\<^sup>T)"
   by (metis comp_associative conv_dist_comp conv_involutive equivalence_top_closed)
 
 lemma point_arc:
   "point x \<Longrightarrow> arc (x * x\<^sup>T)"
   by (simp add: points_arc)
 
 lemma injective_codomain:
   assumes "injective x"
   shows "x * (x \<sqinter> 1) = x \<sqinter> 1"
 proof (rule antisym)
   show "x * (x \<sqinter> 1) \<le> x \<sqinter> 1"
     by (metis assms comp_right_one dual_order.trans inf.boundedI inf.cobounded1 inf.sup_monoid.add_commute mult_right_isotone one_inf_conv)
 next
   show "x \<sqinter> 1 \<le> x * (x \<sqinter> 1)"
     by (metis coreflexive_idempotent inf.cobounded1 inf.cobounded2 mult_left_isotone)
 qed
 
 abbreviation rectangle :: "'a \<Rightarrow> bool"
   where "rectangle x \<equiv> x * top * x = x"
 
 lemma arc_rectangle:
   "arc x \<Longrightarrow> rectangle x"
   using arc_top_arc by blast
 
 section \<open>Relation-Algebraic Semantics of Associative Array Access\<close>
 
 text \<open>
 The following two operations model updating array $x$ at index $y$ to value $z$, 
 and reading the content of array $x$ at index $y$, respectively.
 The read operation uses double brackets to avoid ambiguity with list syntax.
 The remainder of this section shows basic properties of these operations.
 \<close>
 
 abbreviation rel_update :: "'a \<Rightarrow> 'a \<Rightarrow> 'a \<Rightarrow> 'a" ("(_[_\<longmapsto>_])" [70, 65, 65] 61)
   where "x[y\<longmapsto>z] \<equiv> (y \<sqinter> z\<^sup>T) \<squnion> (-y \<sqinter> x)"
 
 abbreviation rel_access :: "'a \<Rightarrow> 'a \<Rightarrow> 'a" ("(2_[[_]])" [70, 65] 65)
   where "x[[y]] \<equiv> x\<^sup>T * y"
 
 text \<open>Theorem 1.1\<close>
 
 lemma update_univalent:
   assumes "univalent x"
     and "vector y"
     and "injective z"
   shows "univalent (x[y\<longmapsto>z])"
 proof -
   have 1: "univalent (y \<sqinter> z\<^sup>T)"
     using assms(3) inf_commute univalent_inf_closed by force
   have "(y \<sqinter> z\<^sup>T)\<^sup>T * (-y \<sqinter> x) = (y\<^sup>T \<sqinter> z) * (-y \<sqinter> x)"
     by (simp add: conv_dist_inf)
   also have "... = z * (y \<sqinter> -y \<sqinter> x)"
     by (metis assms(2) covector_inf_comp_3 inf.sup_monoid.add_assoc inf.sup_monoid.add_commute)
   finally have 2: "(y \<sqinter> z\<^sup>T)\<^sup>T * (-y \<sqinter> x) = bot"
     by simp
   have 3: "vector (-y)"
     using assms(2) vector_complement_closed by simp
   have "(-y \<sqinter> x)\<^sup>T * (y \<sqinter> z\<^sup>T) = (-y\<^sup>T \<sqinter> x\<^sup>T) * (y \<sqinter> z\<^sup>T)"
     by (simp add: conv_complement conv_dist_inf)
   also have "... = x\<^sup>T * (-y \<sqinter> y \<sqinter> z\<^sup>T)"
     using 3 by (metis (mono_tags, hide_lams) conv_complement covector_inf_comp_3 inf.sup_monoid.add_assoc inf.sup_monoid.add_commute)
   finally have 4: "(-y \<sqinter> x)\<^sup>T * (y \<sqinter> z\<^sup>T) = bot"
     by simp
   have 5: "univalent (-y \<sqinter> x)"
     using assms(1) inf_commute univalent_inf_closed by fastforce
   have "(x[y\<longmapsto>z])\<^sup>T * (x[y\<longmapsto>z]) = (y \<sqinter> z\<^sup>T)\<^sup>T * (x[y\<longmapsto>z]) \<squnion> (-y \<sqinter> x)\<^sup>T * (x[y\<longmapsto>z])"
     by (simp add: conv_dist_sup mult_right_dist_sup)
   also have "... = (y \<sqinter> z\<^sup>T)\<^sup>T * (y \<sqinter> z\<^sup>T) \<squnion> (y \<sqinter> z\<^sup>T)\<^sup>T * (-y \<sqinter> x) \<squnion> (-y \<sqinter> x)\<^sup>T * (y \<sqinter> z\<^sup>T) \<squnion> (-y \<sqinter> x)\<^sup>T * (-y \<sqinter> x)"
     by (simp add: mult_left_dist_sup sup_assoc)
   finally show ?thesis
     using 1 2 4 5 by simp
 qed
 
 text \<open>Theorem 1.2\<close>
 
 lemma update_total:
   assumes "total x"
     and "vector y"
     and "regular y"
     and "surjective z"
   shows "total (x[y\<longmapsto>z])"
 proof -
   have "(x[y\<longmapsto>z]) * top = x*top[y\<longmapsto>top*z]"
     by (simp add: assms(2) semiring.distrib_right vector_complement_closed vector_inf_comp conv_dist_comp)
   also have "... = top[y\<longmapsto>top]"
     using assms(1) assms(4) by simp
   also have "... = top"
     using assms(3) regular_complement_top by auto
   finally show ?thesis
     by simp
 qed
 
 text \<open>Theorem 1.3\<close>
 
 lemma update_mapping:
   assumes "mapping x"
     and "vector y"
     and "regular y"
     and "bijective z"
   shows "mapping (x[y\<longmapsto>z])"
   using assms update_univalent update_total by simp
 
 text \<open>Theorem 1.4\<close>
 
 lemma read_injective:
   assumes "injective y"
     and "univalent x"
   shows "injective (x[[y]])"
   using assms injective_mult_closed univalent_conv_injective by blast
 
 text \<open>Theorem 1.5\<close>
 
 lemma read_surjective:
   assumes "surjective y"
     and "total x"
   shows "surjective (x[[y]])"
   using assms surjective_mult_closed total_conv_surjective by blast
 
 text \<open>Theorem 1.6\<close>
 
 lemma read_bijective:
   assumes "bijective y"
     and "mapping x"
   shows "bijective (x[[y]])"
   by (simp add: assms read_injective read_surjective)
 
 text \<open>Theorem 1.7\<close>
 
 lemma read_point:
   assumes "point p"
     and "mapping x"
   shows "point (x[[p]])"
   using assms comp_associative read_injective read_surjective by auto
 
 text \<open>Theorem 1.8\<close>
 
 lemma update_postcondition:
   assumes "point x" "point y"
   shows "x \<sqinter> p = x * y\<^sup>T \<longleftrightarrow> p[[x]] = y"
   apply (rule iffI)
   subgoal by (metis assms comp_associative conv_dist_comp conv_involutive covector_inf_comp_3 equivalence_top_closed vector_covector)
   subgoal
     apply (rule antisym)
     subgoal by (metis assms conv_dist_comp conv_involutive inf.boundedI inf.cobounded1 vector_covector vector_restrict_comp_conv)
     subgoal by (smt assms comp_associative conv_dist_comp conv_involutive covector_restrict_comp_conv dense_conv_closed equivalence_top_closed inf.boundedI shunt_mapping vector_covector preorder_idempotent)
     done
   done
 
 text \<open>Back and von Wright's array independence requirements \cite{BackWright1998}, 
   later also lens laws \cite{FosterGreenwaldMoorePierceSchmitt2007}\<close>
 
 lemma put_get:
   assumes "vector y" "surjective y" "vector z"
   shows "(x[y\<longmapsto>z])[[y]] = z"
 proof -
   have "(x[y\<longmapsto>z])[[y]] = (y\<^sup>T \<sqinter> z) * y \<squnion> (-y\<^sup>T \<sqinter> x\<^sup>T) * y"
     by (simp add: conv_complement conv_dist_inf conv_dist_sup mult_right_dist_sup)
   also have "... = z * y"
   proof -
     have "(-y\<^sup>T \<sqinter> x\<^sup>T) * y = bot"
       by (metis assms(1) covector_inf_comp_3 inf_commute conv_complement mult_right_zero p_inf vector_complement_closed)
     thus ?thesis
       by (simp add: assms covector_inf_comp_3 inf_commute)
   qed
   also have "... = z"
     by (metis assms(2,3) mult_assoc)
   finally show ?thesis
     .
 qed
 
 lemma put_put:
   "(x[y\<longmapsto>z])[y\<longmapsto>w] = x[y\<longmapsto>w]"
   by (metis inf_absorb2 inf_commute inf_le1 inf_sup_distrib1 maddux_3_13 sup_inf_absorb)
 
 lemma get_put:
   assumes "point y"
   shows "x[y\<longmapsto>x[[y]]] = x"
 proof -
   have "x[y\<longmapsto>x[[y]]] = (y \<sqinter> y\<^sup>T * x) \<squnion> (-y \<sqinter> x)"
     by (simp add: conv_dist_comp)
   also have "... = (y \<sqinter> x) \<squnion> (-y \<sqinter> x)"
   proof -
     have "y \<sqinter> y\<^sup>T * x = y \<sqinter> x"
     proof (rule antisym)
       have "y \<sqinter> y\<^sup>T * x = (y \<sqinter> y\<^sup>T) * x"
         by (simp add: assms vector_inf_comp)
       also have "(y \<sqinter> y\<^sup>T) * x = y * y\<^sup>T * x"
         by (simp add: assms vector_covector)
       also have "... \<le> x"
         using assms comp_isotone by fastforce
       finally show "y \<sqinter> y\<^sup>T * x \<le> y \<sqinter> x"
         by simp
       have "y \<sqinter> x \<le> y\<^sup>T * x"
         by (simp add: assms vector_restrict_comp_conv)
       thus "y \<sqinter> x \<le> y \<sqinter> y\<^sup>T * x"
         by simp
     qed
     thus ?thesis
       by simp
   qed
   also have "... = x"
   proof -
     have "regular y"
       using assms bijective_regular by blast
     thus ?thesis
       by (metis inf.sup_monoid.add_commute maddux_3_11_pp)
   qed
   finally show ?thesis
     .
 qed
 
+lemma update_inf:
+  "u \<le> y \<Longrightarrow> (x[y\<longmapsto>z]) \<sqinter> u = z\<^sup>T \<sqinter> u"
+  by (smt comp_inf.mult_right_dist_sup comp_inf.semiring.mult_zero_right inf.left_commute inf.sup_monoid.add_assoc inf_absorb2 p_inf sup_bot_right inf.sup_monoid.add_commute)
+
+lemma update_inf_same:
+  "(x[y\<longmapsto>z]) \<sqinter> y = z\<^sup>T \<sqinter> y"
+  by (simp add: update_inf)
+
+lemma update_inf_different:
+  "u \<le> -y \<Longrightarrow> (x[y\<longmapsto>z]) \<sqinter> u = x \<sqinter> u"
+  by (smt inf.right_idem inf.sup_monoid.add_commute inf.sup_relative_same_increasing inf_import_p maddux_3_13 sup.cobounded2 update_inf_same)
+
 end
 
 section \<open>Relation-Algebraic Semantics of Disjoint-Set Forests\<close>
 
 text \<open>
 A disjoint-set forest represents a partition of a set into equivalence classes.
 We take the represented equivalence relation as the semantics of a forest.
 It is obtained by operation \<open>fc\<close> below.
 Additionally, operation \<open>wcc\<close> giving the weakly connected components of a graph will be used for the semantics of the union of two disjoint sets.
 Finally, operation \<open>root\<close> yields the root of a component tree, that is, the representative of a set containing a given element.
 This section defines these operations and derives their properties.
 \<close>
 
 context stone_kleene_relation_algebra
 begin
 
 lemma equivalence_star_closed:
   "equivalence x \<Longrightarrow> equivalence (x\<^sup>\<star>)"
   by (simp add: conv_star_commute star.circ_reflexive star.circ_transitive_equal)
 
 lemma equivalence_plus_closed:
   "equivalence x \<Longrightarrow> equivalence (x\<^sup>+)"
   by (simp add: conv_star_commute star.circ_reflexive star.circ_sup_one_left_unfold star.circ_transitive_equal)
 
 lemma reachable_without_loops:
   "x\<^sup>\<star> = (x \<sqinter> -1)\<^sup>\<star>"
 proof (rule antisym)
   have "x * (x \<sqinter> -1)\<^sup>\<star> = (x \<sqinter> 1) * (x \<sqinter> -1)\<^sup>\<star> \<squnion> (x \<sqinter> -1) * (x \<sqinter> -1)\<^sup>\<star>"
     by (metis maddux_3_11_pp mult_right_dist_sup regular_one_closed)
   also have "... \<le> (x \<sqinter> -1)\<^sup>\<star>"
     by (metis inf.cobounded2 le_supI mult_left_isotone star.circ_circ_mult star.left_plus_below_circ star_involutive star_one)
   finally show "x\<^sup>\<star> \<le> (x \<sqinter> -1)\<^sup>\<star>"
     by (metis inf.cobounded2 maddux_3_11_pp regular_one_closed star.circ_circ_mult star.circ_sup_2 star_involutive star_sub_one)
 next
   show "(x \<sqinter> -1)\<^sup>\<star> \<le> x\<^sup>\<star>"
     by (simp add: star_isotone)
 qed
 
+lemma plus_reachable_without_loops:
+  "x\<^sup>+ = (x \<sqinter> -1)\<^sup>+ \<squnion> (x \<sqinter> 1)"
+  by (metis comp_associative maddux_3_11_pp regular_one_closed star.circ_back_loop_fixpoint star.circ_loop_fixpoint sup_assoc reachable_without_loops)
+
 lemma star_plus_loops:
   "x\<^sup>\<star> \<squnion> 1 = x\<^sup>+ \<squnion> 1"
   using star.circ_plus_one star_left_unfold_equal sup_commute by auto
 
 lemma star_plus_without_loops:
   "x\<^sup>\<star> \<sqinter> -1 = x\<^sup>+ \<sqinter> -1"
   by (metis maddux_3_13 star_left_unfold_equal)
 
 text \<open>Theorem 4.2\<close>
 
 lemma omit_redundant_points:
   assumes "point p"
   shows "p \<sqinter> x\<^sup>\<star> = (p \<sqinter> 1) \<squnion> (p \<sqinter> x) * (-p \<sqinter> x)\<^sup>\<star>"
 proof (rule antisym)
   let ?p = "p \<sqinter> 1"
   have "?p * x * (-p \<sqinter> x)\<^sup>\<star> * ?p \<le> ?p * top * ?p"
     by (metis comp_associative mult_left_isotone mult_right_isotone top.extremum)
   also have "... \<le> ?p"
     by (simp add: assms injective_codomain vector_inf_one_comp)
   finally have "?p * x * (-p \<sqinter> x)\<^sup>\<star> * ?p * x \<le> ?p * x"
     using mult_left_isotone by blast
   hence "?p * x * (-p \<sqinter> x)\<^sup>\<star> * (p \<sqinter> x) \<le> ?p * x"
     by (simp add: assms comp_associative vector_inf_one_comp)
   also have 1: "... \<le> ?p * x * (-p \<sqinter> x)\<^sup>\<star>"
     using mult_right_isotone star.circ_reflexive by fastforce
   finally have "?p * x * (-p \<sqinter> x)\<^sup>\<star> * (p \<sqinter> x) \<squnion> ?p * x * (-p \<sqinter> x)\<^sup>\<star> * (-p \<sqinter> x) \<le> ?p * x * (-p \<sqinter> x)\<^sup>\<star>"
     by (simp add: mult_right_isotone star.circ_plus_same star.left_plus_below_circ mult_assoc)
   hence "?p * x * (-p \<sqinter> x)\<^sup>\<star> * ((p \<squnion> -p) \<sqinter> x) \<le> ?p * x * (-p \<sqinter> x)\<^sup>\<star>"
     by (simp add: comp_inf.mult_right_dist_sup mult_left_dist_sup)
   hence "?p * x * (-p \<sqinter> x)\<^sup>\<star> * x \<le> ?p * x * (-p \<sqinter> x)\<^sup>\<star>"
     by (metis assms bijective_regular inf.absorb2 inf.cobounded1 inf.sup_monoid.add_commute shunting_p)
   hence "?p * x * (-p \<sqinter> x)\<^sup>\<star> * x \<squnion> ?p * x \<le> ?p * x * (-p \<sqinter> x)\<^sup>\<star>"
     using 1 by simp
   hence "?p * (1 \<squnion> x * (-p \<sqinter> x)\<^sup>\<star>) * x \<le> ?p * x * (-p \<sqinter> x)\<^sup>\<star>"
     by (simp add: comp_associative mult_left_dist_sup mult_right_dist_sup)
   also have "... \<le> ?p * (1 \<squnion> x * (-p \<sqinter> x)\<^sup>\<star>)"
     by (simp add: comp_associative mult_right_isotone)
   finally have "?p * x\<^sup>\<star> \<le> ?p * (1 \<squnion> x * (-p \<sqinter> x)\<^sup>\<star>)"
     using star_right_induct by (meson dual_order.trans le_supI mult_left_sub_dist_sup_left mult_sub_right_one)
   also have "... = ?p \<squnion> ?p * x * (-p \<sqinter> x)\<^sup>\<star>"
     by (simp add: comp_associative semiring.distrib_left)
   finally show "p \<sqinter> x\<^sup>\<star> \<le> ?p \<squnion> (p \<sqinter> x) * (-p \<sqinter> x)\<^sup>\<star>"
     by (simp add: assms vector_inf_one_comp)
   show "?p \<squnion> (p \<sqinter> x) * (-p \<sqinter> x)\<^sup>\<star> \<le> p \<sqinter> x\<^sup>\<star>"
     by (metis assms comp_isotone inf.boundedI inf.cobounded1 inf.coboundedI2 inf.sup_monoid.add_commute le_supI star.circ_increasing star.circ_transitive_equal star_isotone star_left_unfold_equal sup.cobounded1 vector_export_comp)
 qed
 
 text \<open>Weakly connected components\<close>
 
 abbreviation "wcc x \<equiv> (x \<squnion> x\<^sup>T)\<^sup>\<star>"
 
 text \<open>Theorem 5.1\<close>
 
 lemma wcc_equivalence:
   "equivalence (wcc x)"
   apply (intro conjI)
   subgoal by (simp add: star.circ_reflexive)
   subgoal by (simp add: star.circ_transitive_equal)
   subgoal by (simp add: conv_dist_sup conv_star_commute sup_commute)
   done
 
 text \<open>Theorem 5.2\<close>
 
 lemma wcc_increasing:
   "x \<le> wcc x"
   by (simp add: star.circ_sub_dist_1)
 
 lemma wcc_isotone:
   "x \<le> y \<Longrightarrow> wcc x \<le> wcc y"
   using conv_isotone star_isotone sup_mono by blast
 
 lemma wcc_idempotent:
   "wcc (wcc x) = wcc x"
   using star_involutive wcc_equivalence by auto
 
 text \<open>Theorem 5.3\<close>
 
 lemma wcc_below_wcc:
   "x \<le> wcc y \<Longrightarrow> wcc x \<le> wcc y"
   using wcc_idempotent wcc_isotone by fastforce
 
 text \<open>Theorem 5.4\<close>
 
 lemma wcc_bot:
   "wcc bot = 1"
   by (simp add: star.circ_zero)
 
 lemma wcc_one:
   "wcc 1 = 1"
   by (simp add: star_one)
 
 text \<open>Theorem 5.5\<close>
 
 lemma wcc_top:
   "wcc top = top"
   by (simp add: star.circ_top)
 
 text \<open>Theorem 5.6\<close>
 
 lemma wcc_with_loops:
   "wcc x = wcc (x \<squnion> 1)"
   by (metis conv_dist_sup star_decompose_1 star_sup_one sup_commute symmetric_one_closed)
 
 lemma wcc_without_loops:
   "wcc x = wcc (x \<sqinter> -1)"
   by (metis conv_star_commute star_sum reachable_without_loops)
 
 lemma forest_components_wcc:
   "injective x \<Longrightarrow> wcc x = forest_components x"
   by (simp add: cancel_separate_1)
 
 text \<open>Components of a forest, which is represented using edges directed towards the roots\<close>
 
 abbreviation "fc x \<equiv> x\<^sup>\<star> * x\<^sup>T\<^sup>\<star>"
 
 text \<open>Theorem 2.1\<close>
 
 lemma fc_equivalence:
   "univalent x \<Longrightarrow> equivalence (fc x)"
   apply (intro conjI)
   subgoal by (simp add: reflexive_mult_closed star.circ_reflexive)
   subgoal by (metis cancel_separate_1 eq_iff star.circ_transitive_equal)
   subgoal by (simp add: conv_dist_comp conv_star_commute)
   done
 
 text \<open>Theorem 2.2\<close>
 
 lemma fc_increasing:
   "x \<le> fc x"
   by (metis le_supE mult_left_isotone star.circ_back_loop_fixpoint star.circ_increasing)
 
 text \<open>Theorem 2.3\<close>
 
 lemma fc_isotone:
   "x \<le> y \<Longrightarrow> fc x \<le> fc y"
   by (simp add: comp_isotone conv_isotone star_isotone)
 
 text \<open>Theorem 2.4\<close>
 
 lemma fc_idempotent:
   "univalent x \<Longrightarrow> fc (fc x) = fc x"
   by (metis fc_equivalence cancel_separate_1 star.circ_transitive_equal star_involutive)
 
 text \<open>Theorem 2.5\<close>
 
 lemma fc_star:
   "univalent x \<Longrightarrow> (fc x)\<^sup>\<star> = fc x"
   using fc_equivalence fc_idempotent star.circ_transitive_equal by simp
 
 lemma fc_plus:
   "univalent x \<Longrightarrow> (fc x)\<^sup>+ = fc x"
   by (metis fc_star star.circ_decompose_9)
 
 text \<open>Theorem 2.6\<close>
 
 lemma fc_bot:
   "fc bot = 1"
   by (simp add: star.circ_zero)
 
 lemma fc_one:
   "fc 1 = 1"
   by (simp add: star_one)
 
 text \<open>Theorem 2.7\<close>
 
 lemma fc_top:
   "fc top = top"
   by (simp add: star.circ_top)
 
 text \<open>Theorem 5.7\<close>
 
 lemma fc_wcc:
   "univalent x \<Longrightarrow> wcc x = fc x"
   by (simp add: fc_star star_decompose_1)
 
+lemma fc_via_root:
+  assumes "total (p\<^sup>\<star> * (p \<sqinter> 1))"
+  shows "fc p = p\<^sup>\<star> * (p \<sqinter> 1) * p\<^sup>T\<^sup>\<star>"
+proof (rule antisym)
+  have "1 \<le> p\<^sup>\<star> * (p \<sqinter> 1) * p\<^sup>T\<^sup>\<star>"
+    by (smt assms comp_associative conv_dist_comp conv_star_commute coreflexive_idempotent coreflexive_symmetric inf.cobounded2 total_var)
+  hence "fc p \<le> p\<^sup>\<star> * p\<^sup>\<star> * (p \<sqinter> 1) * p\<^sup>T\<^sup>\<star> * p\<^sup>T\<^sup>\<star>"
+    by (metis comp_right_one mult_left_isotone mult_right_isotone mult_assoc)
+  thus "fc p \<le> p\<^sup>\<star> * (p \<sqinter> 1) * p\<^sup>T\<^sup>\<star>"
+    by (simp add: star.circ_transitive_equal mult_assoc)
+  show "p\<^sup>\<star> * (p \<sqinter> 1) * p\<^sup>T\<^sup>\<star> \<le> fc p"
+    by (metis comp_isotone inf.cobounded2 mult_1_right order.refl)
+qed
+
 text \<open>Theorem 4.1\<close>
 
 lemma update_acyclic_1:
   assumes "acyclic (p \<sqinter> -1)"
     and "point y"
-    and "point w"
-    and "y \<le> p\<^sup>T\<^sup>\<star> * w"
+    and "vector w"
+    and "w \<le> p\<^sup>\<star> * y"
   shows "acyclic ((p[w\<longmapsto>y]) \<sqinter> -1)"
 proof -
   let ?p = "p[w\<longmapsto>y]"
-  have "w \<le> p\<^sup>\<star> * y"
-    using assms(2-4) by (metis (no_types, lifting) bijective_reverse conv_star_commute)
-  hence "w * y\<^sup>T \<le> p\<^sup>\<star>"
-    using assms(2) shunt_bijective by blast
+  have "w * y\<^sup>T \<le> p\<^sup>\<star>"
+    using assms(2,4) shunt_bijective by blast
   hence "w * y\<^sup>T \<le> (p \<sqinter> -1)\<^sup>\<star>"
     using reachable_without_loops by auto
   hence "w * y\<^sup>T \<sqinter> -1 \<le> (p \<sqinter> -1)\<^sup>\<star> \<sqinter> -1"
     by (simp add: inf.coboundedI2 inf.sup_monoid.add_commute)
   also have "... \<le> (p \<sqinter> -1)\<^sup>+"
     by (simp add: star_plus_without_loops)
   finally have 1: "w \<sqinter> y\<^sup>T \<sqinter> -1 \<le> (p \<sqinter> -1)\<^sup>+"
     using assms(2,3) vector_covector by auto
   have "?p \<sqinter> -1 = (w \<sqinter> y\<^sup>T \<sqinter> -1) \<squnion> (-w \<sqinter> p \<sqinter> -1)"
     by (simp add: inf_sup_distrib2)
   also have "... \<le> (p \<sqinter> -1)\<^sup>+ \<squnion> (-w \<sqinter> p \<sqinter> -1)"
     using 1 sup_left_isotone by blast
   also have "... \<le> (p \<sqinter> -1)\<^sup>+ \<squnion> (p \<sqinter> -1)"
     using comp_inf.mult_semi_associative sup_right_isotone by auto
   also have "... = (p \<sqinter> -1)\<^sup>+"
     by (metis star.circ_back_loop_fixpoint sup.right_idem)
   finally have "(?p \<sqinter> -1)\<^sup>+ \<le> (p \<sqinter> -1)\<^sup>+"
     by (metis comp_associative comp_isotone star.circ_transitive_equal star.left_plus_circ star_isotone)
   also have "... \<le> -1"
     using assms(1) by blast
   finally show ?thesis
     by simp
 qed
 
+lemma update_acyclic_2:
+  assumes "acyclic (p \<sqinter> -1)"
+    and "point y"
+    and "point x"
+    and "y \<le> p\<^sup>T\<^sup>\<star> * x"
+    and "univalent p"
+    and "p\<^sup>T * y \<le> y"
+  shows "acyclic ((p[p\<^sup>T\<^sup>\<star>*x\<longmapsto>y]) \<sqinter> -1)"
+proof -
+  have "p\<^sup>T * p\<^sup>\<star> * y = p\<^sup>T * p * p\<^sup>\<star> * y \<squnion> p\<^sup>T * y"
+    by (metis comp_associative mult_left_dist_sup star.circ_loop_fixpoint)
+  also have "... \<le> p\<^sup>\<star> * y"
+    by (metis assms(5,6) comp_right_one le_supI le_supI2 mult_left_isotone star.circ_loop_fixpoint star.circ_transitive_equal)
+  finally have "p\<^sup>T\<^sup>\<star> * x \<le> p\<^sup>\<star> * y"
+    by (simp add: assms(2-4) bijective_reverse conv_star_commute comp_associative star_left_induct)
+  thus ?thesis
+    by (simp add: assms(1-3) vector_mult_closed update_acyclic_1)
+qed
+
+lemma update_acyclic_3:
+  assumes "acyclic (p \<sqinter> -1)"
+    and "point y"
+    and "point w"
+    and "y \<le> p\<^sup>T\<^sup>\<star> * w"
+  shows "acyclic ((p[w\<longmapsto>y]) \<sqinter> -1)"
+  by (simp add: assms bijective_reverse conv_star_commute update_acyclic_1)
+
 lemma rectangle_star_rectangle:
   "rectangle a \<Longrightarrow> a * x\<^sup>\<star> * a \<le> a"
   by (metis mult_left_isotone mult_right_isotone top.extremum)
 
 lemma arc_star_arc:
   "arc a \<Longrightarrow> a * x\<^sup>\<star> * a \<le> a"
   using arc_top_arc rectangle_star_rectangle by blast
 
 lemma star_rectangle_decompose:
   assumes "rectangle a"
   shows "(a \<squnion> x)\<^sup>\<star> = x\<^sup>\<star> \<squnion> x\<^sup>\<star> * a * x\<^sup>\<star>"
 proof (rule antisym)
   have 1: "1 \<le> x\<^sup>\<star> \<squnion> x\<^sup>\<star> * a * x\<^sup>\<star>"
     by (simp add: star.circ_reflexive sup.coboundedI1)
   have "(a \<squnion> x) * (x\<^sup>\<star> \<squnion> x\<^sup>\<star> * a * x\<^sup>\<star>) = a * x\<^sup>\<star> \<squnion> a * x\<^sup>\<star> * a * x\<^sup>\<star> \<squnion> x\<^sup>+ \<squnion> x\<^sup>+ * a * x\<^sup>\<star>"
     by (metis comp_associative semiring.combine_common_factor semiring.distrib_left sup_commute)
   also have "... = a * x\<^sup>\<star> \<squnion> x\<^sup>+ \<squnion> x\<^sup>+ * a * x\<^sup>\<star>"
     using assms rectangle_star_rectangle by (simp add: mult_left_isotone sup_absorb1)
   also have "... = x\<^sup>+ \<squnion> x\<^sup>\<star> * a * x\<^sup>\<star>"
     by (metis comp_associative star.circ_loop_fixpoint sup_assoc sup_commute)
   also have "... \<le> x\<^sup>\<star> \<squnion> x\<^sup>\<star> * a * x\<^sup>\<star>"
     using star.left_plus_below_circ sup_left_isotone by auto
   finally show "(a \<squnion> x)\<^sup>\<star> \<le> x\<^sup>\<star> \<squnion> x\<^sup>\<star> * a * x\<^sup>\<star>"
     using 1 by (metis comp_right_one le_supI star_left_induct)
 next
   show "x\<^sup>\<star> \<squnion> x\<^sup>\<star> * a * x\<^sup>\<star> \<le> (a \<squnion> x)\<^sup>\<star>"
     by (metis comp_isotone le_supE le_supI star.circ_increasing star.circ_transitive_equal star_isotone sup_ge2)
 qed
 
 lemma star_arc_decompose:
   "arc a \<Longrightarrow> (a \<squnion> x)\<^sup>\<star> = x\<^sup>\<star> \<squnion> x\<^sup>\<star> * a * x\<^sup>\<star>"
   using arc_top_arc star_rectangle_decompose by blast
 
 lemma plus_rectangle_decompose:
   assumes "rectangle a"
   shows "(a \<squnion> x)\<^sup>+ = x\<^sup>+ \<squnion> x\<^sup>\<star> * a * x\<^sup>\<star>"
 proof -
   have "(a \<squnion> x)\<^sup>+ = (a \<squnion> x) * (x\<^sup>\<star> \<squnion> x\<^sup>\<star> * a * x\<^sup>\<star>)"
     by (simp add: assms star_rectangle_decompose)
   also have "... = a * x\<^sup>\<star> \<squnion> a * x\<^sup>\<star> * a * x\<^sup>\<star> \<squnion> x\<^sup>+ \<squnion> x\<^sup>+ * a * x\<^sup>\<star>"
     by (metis comp_associative semiring.combine_common_factor semiring.distrib_left sup_commute)
   also have "... = a * x\<^sup>\<star> \<squnion> x\<^sup>+ \<squnion> x\<^sup>+ * a * x\<^sup>\<star>"
     using assms rectangle_star_rectangle by (simp add: mult_left_isotone sup_absorb1)
   also have "... = x\<^sup>+ \<squnion> x\<^sup>\<star> * a * x\<^sup>\<star>"
     by (metis comp_associative star.circ_loop_fixpoint sup_assoc sup_commute)
   finally show ?thesis
     by simp
 qed
 
 text \<open>Theorem 6.1\<close>
 
 lemma plus_arc_decompose:
   "arc a \<Longrightarrow> (a \<squnion> x)\<^sup>+ = x\<^sup>+ \<squnion> x\<^sup>\<star> * a * x\<^sup>\<star>"
   using arc_top_arc plus_rectangle_decompose by blast
 
 text \<open>Theorem 6.2\<close>
 
-lemma update_acyclic_2:
+lemma update_acyclic_4:
   assumes "acyclic (p \<sqinter> -1)"
     and "point y"
     and "point w"
     and "y \<sqinter> p\<^sup>\<star> * w = bot"
   shows "acyclic ((p[w\<longmapsto>y]) \<sqinter> -1)"
 proof -
   let ?p = "p[w\<longmapsto>y]"
   have "y\<^sup>T * p\<^sup>\<star> * w \<le> -1"
     using assms(4) comp_associative pseudo_complement schroeder_3_p by auto
   hence 1: "p\<^sup>\<star> * w * y\<^sup>T * p\<^sup>\<star> \<le> -1"
     by (metis comp_associative comp_commute_below_diversity star.circ_transitive_equal)
   have "?p \<sqinter> -1 \<le> (w \<sqinter> y\<^sup>T) \<squnion> (p \<sqinter> -1)"
     by (metis comp_inf.mult_right_dist_sup dual_order.trans inf.cobounded1 inf.coboundedI2 inf.sup_monoid.add_assoc le_supI sup.cobounded1 sup_ge2)
   also have "... = w * y\<^sup>T \<squnion> (p \<sqinter> -1)"
     using assms(2,3) by (simp add: vector_covector)
   finally have "(?p \<sqinter> -1)\<^sup>+ \<le> (w * y\<^sup>T \<squnion> (p \<sqinter> -1))\<^sup>+"
     by (simp add: comp_isotone star_isotone)
   also have "... = (p \<sqinter> -1)\<^sup>+ \<squnion> (p \<sqinter> -1)\<^sup>\<star> * w * y\<^sup>T * (p \<sqinter> -1)\<^sup>\<star>"
     using assms(2,3) plus_arc_decompose points_arc by (simp add: comp_associative)
   also have "... \<le> (p \<sqinter> -1)\<^sup>+ \<squnion> p\<^sup>\<star> * w * y\<^sup>T * p\<^sup>\<star>"
     using reachable_without_loops by auto
   also have "... \<le> -1"
     using 1 assms(1) by simp
   finally show ?thesis
     by simp
 qed
 
 lemma acyclic_down_closed:
   "x \<le> y \<Longrightarrow> acyclic y \<Longrightarrow> acyclic x"
   using comp_isotone star_isotone by fastforce
 
 text \<open>Theorem 6.3\<close>
 
-lemma update_acyclic_3:
+lemma update_acyclic_5:
   assumes "acyclic (p \<sqinter> -1)"
     and "point w"
   shows "acyclic ((p[w\<longmapsto>w]) \<sqinter> -1)"
 proof -
   let ?p = "p[w\<longmapsto>w]"
   have "?p \<sqinter> -1 \<le> (w \<sqinter> w\<^sup>T \<sqinter> -1) \<squnion> (p \<sqinter> -1)"
     by (metis comp_inf.mult_right_dist_sup inf.cobounded2 inf.sup_monoid.add_assoc sup_right_isotone)
   also have "... = p \<sqinter> -1"
     using assms(2) by (metis comp_inf.covector_complement_closed equivalence_top_closed inf_top.right_neutral maddux_3_13 pseudo_complement regular_closed_top regular_one_closed vector_covector vector_top_closed)
   finally show ?thesis
     using assms(1) acyclic_down_closed by blast
 qed
 
 text \<open>Root of the tree containing point $x$ in the disjoint-set forest $p$\<close>
 
 abbreviation "root p x \<equiv> p\<^sup>T\<^sup>\<star> * x \<sqinter> (p \<sqinter> 1) * top"
 
 text \<open>Theorem 3.1\<close>
 
 lemma root_var:
   "root p x = (p \<sqinter> 1) * p\<^sup>T\<^sup>\<star> * x"
   by (simp add: coreflexive_comp_top_inf inf_commute mult_assoc)
 
 text \<open>Theorem 3.2\<close>
 
 lemma root_successor_loop:
   "univalent p \<Longrightarrow> root p x = p[[root p x]]"
   by (metis root_var injective_codomain comp_associative conv_dist_inf coreflexive_symmetric equivalence_one_closed inf.cobounded2 univalent_conv_injective)
 
 lemma root_transitive_successor_loop:
   "univalent p \<Longrightarrow> root p x = p\<^sup>T\<^sup>\<star> * (root p x)"
   by (metis mult_1_right star_one star_simulation_right_equal root_successor_loop)
 
 text \<open>The root of a tree of a node belongs to the same component as the node.\<close>
 
 lemma root_same_component:
   "injective x \<Longrightarrow> root p x * x\<^sup>T \<le> fc p"
   by (metis comp_associative coreflexive_comp_top_inf eq_refl inf.sup_left_divisibility inf.sup_monoid.add_commute mult_isotone star.circ_circ_mult star.circ_right_top star.circ_transitive_equal star_one star_outer_increasing test_preserves_equation top_greatest)
 
 lemma root_vector:
   "vector x \<Longrightarrow> vector (root p x)"
   by (simp add: vector_mult_closed root_var)
 
 lemma root_vector_inf:
   "vector x \<Longrightarrow> root p x * x\<^sup>T = root p x \<sqinter> x\<^sup>T"
   by (simp add: vector_covector root_vector)
 
 lemma root_same_component_vector:
   "injective x \<Longrightarrow> vector x \<Longrightarrow> root p x \<sqinter> x\<^sup>T \<le> fc p"
   using root_same_component root_vector_inf by fastforce
 
 lemma univalent_root_successors:
   assumes "univalent p"
   shows "(p \<sqinter> 1) * p\<^sup>\<star> = p \<sqinter> 1"
 proof (rule antisym)
   have "(p \<sqinter> 1) * p \<le> p \<sqinter> 1"
     by (smt assms(1) comp_inf.mult_semi_associative conv_dist_comp conv_dist_inf conv_order equivalence_one_closed inf.absorb1 inf.sup_monoid.add_assoc injective_codomain)
   thus "(p \<sqinter> 1) * p\<^sup>\<star> \<le> p \<sqinter> 1"
     using star_right_induct_mult by blast
   show "p \<sqinter> 1 \<le> (p \<sqinter> 1) * p\<^sup>\<star>"
     by (metis coreflexive_idempotent inf_le1 inf_le2 mult_right_isotone order_trans star.circ_increasing)
 qed
 
 lemma same_component_same_root_sub:
   assumes "univalent p"
     and "bijective y"
     and "x * y\<^sup>T \<le> fc p"
   shows "root p x \<le> root p y"
 proof -
   have "root p x * y\<^sup>T \<le> (p \<sqinter> 1) * p\<^sup>T\<^sup>\<star>"
     by (smt assms(1,3) mult_isotone mult_assoc root_var fc_plus fc_star eq_iff univalent_root_successors)
   thus ?thesis
     by (simp add: assms(2) shunt_bijective root_var)
 qed
 
 lemma same_component_same_root:
   assumes "univalent p"
     and "bijective x"
     and "bijective y"
     and "x * y\<^sup>T \<le> fc p"
   shows "root p x = root p y"
 proof (rule antisym)
   show "root p x \<le> root p y"
     using assms(1,3,4) same_component_same_root_sub by blast
   have "y * x\<^sup>T \<le> fc p"
     using assms(1,4) fc_equivalence conv_dist_comp conv_isotone by fastforce
   thus "root p y \<le> root p x"
     using assms(1,2) same_component_same_root_sub by blast
 qed
 
 lemma same_roots_sub:
   assumes "univalent q"
     and "p \<sqinter> 1 \<le> q \<sqinter> 1"
     and "fc p \<le> fc q"
   shows "p\<^sup>\<star> * (p \<sqinter> 1) \<le> q\<^sup>\<star> * (q \<sqinter> 1)"
 proof -
   have "p\<^sup>\<star> * (p \<sqinter> 1) \<le> p\<^sup>\<star> * (q \<sqinter> 1)"
     using assms(2) mult_right_isotone by auto
   also have "... \<le> fc p * (q \<sqinter> 1)"
     using mult_left_isotone mult_right_isotone star.circ_reflexive by fastforce
   also have "... \<le> fc q * (q \<sqinter> 1)"
     by (simp add: assms(3) mult_left_isotone)
   also have "... = q\<^sup>\<star> * (q \<sqinter> 1)"
     by (metis assms(1) conv_dist_comp conv_dist_inf conv_star_commute inf_commute one_inf_conv symmetric_one_closed mult_assoc univalent_root_successors)
   finally show ?thesis
     .
 qed
 
 lemma same_roots:
   assumes "univalent p"
     and "univalent q"
     and "p \<sqinter> 1 = q \<sqinter> 1"
     and "fc p = fc q"
   shows "p\<^sup>\<star> * (p \<sqinter> 1) = q\<^sup>\<star> * (q \<sqinter> 1)"
   by (smt assms conv_dist_comp conv_dist_inf conv_involutive conv_star_commute inf_commute one_inf_conv symmetric_one_closed root_var univalent_root_successors)
 
 lemma same_root:
   assumes "univalent p"
     and "univalent q"
     and "p \<sqinter> 1 = q \<sqinter> 1"
     and "fc p = fc q"
   shows "root p x = root q x"
   by (metis assms mult_assoc root_var univalent_root_successors)
 
+lemma loop_root:
+  assumes "injective x"
+    and "x = p[[x]]"
+  shows "x = root p x"
+proof (rule antisym)
+  have "x \<le> p * x"
+    by (metis assms comp_associative comp_right_one conv_order equivalence_one_closed ex231c inf.orderE inf.sup_monoid.add_commute mult_left_isotone mult_right_isotone one_inf_conv)
+  hence "x = (p \<sqinter> 1) * x"
+    by (simp add: assms(1) inf_absorb2 injective_comp_right_dist_inf)
+  thus "x \<le> root p x"
+    by (metis assms(2) coreflexive_comp_top_inf inf.boundedI inf.cobounded1 inf.cobounded2 mult_isotone star.circ_increasing)
+next
+  show "root p x \<le> x"
+    using assms(2) le_infI1 star_left_induct_mult by auto
+qed
+
+lemma test_comp_test_inf:
+  "(x \<sqinter> 1) * y * (z \<sqinter> 1) = (x \<sqinter> 1) * y \<sqinter> y * (z \<sqinter> 1)"
+  by (smt comp_right_one comp_right_subdist_inf coreflexive_comp_top_inf inf.left_commute inf.orderE inf_le2 mult_assoc)
+
+lemma test_comp_test_top:
+  "y \<sqinter> (x \<sqinter> 1) * top * (z \<sqinter> 1) = (x \<sqinter> 1) * y * (z \<sqinter> 1)"
+proof -
+  have "\<forall>u v . (v \<sqinter> u\<^sup>T)\<^sup>T = v\<^sup>T \<sqinter> u"
+    using conv_dist_inf by auto
+  thus ?thesis
+    by (smt conv_dist_comp conv_involutive coreflexive_comp_top_inf inf.cobounded2 inf.left_commute inf.sup_monoid.add_commute symmetric_one_closed mult_assoc symmetric_top_closed)
+qed
+
+lemma one_loop:
+  assumes "acyclic (p \<sqinter> -1)"
+    and "univalent p"
+  shows "(p \<sqinter> 1) * (p\<^sup>T \<sqinter> -1)\<^sup>+ * (p \<sqinter> 1) = bot"
+proof -
+  have "p\<^sup>T\<^sup>+ \<sqinter> (p \<sqinter> 1) * top * (p \<sqinter> 1) = (p \<sqinter> 1) * p\<^sup>T\<^sup>+ * (p \<sqinter> 1)"
+    by (simp add: test_comp_test_top)
+  also have "... \<le> p\<^sup>T\<^sup>\<star> * (p \<sqinter> 1)"
+    by (simp add: inf.coboundedI2 mult_left_isotone star.circ_mult_upper_bound star.circ_reflexive star.left_plus_below_circ)
+  also have "... = p \<sqinter> 1"
+    by (metis assms(2) conv_dist_comp conv_dist_inf conv_star_commute inf_commute one_inf_conv symmetric_one_closed univalent_root_successors)
+  also have "... \<le> 1"
+    by simp
+  finally have "(p \<sqinter> 1) * top * (p \<sqinter> 1) \<le> -(p\<^sup>T\<^sup>+ \<sqinter> -1)"
+    using p_antitone p_antitone_iff p_shunting_swap by blast
+  hence "(p \<sqinter> 1)\<^sup>T * (p\<^sup>T\<^sup>+ \<sqinter> -1) * (p \<sqinter> 1)\<^sup>T \<le> bot"
+    using triple_schroeder_p p_top by blast
+  hence "(p \<sqinter> 1) * (p\<^sup>T\<^sup>+ \<sqinter> -1) * (p \<sqinter> 1) = bot"
+    by (simp add: coreflexive_symmetric le_bot)
+  thus ?thesis
+    by (smt assms(1) conv_complement conv_dist_comp conv_dist_inf conv_star_commute inf_absorb1 star.circ_plus_same symmetric_one_closed reachable_without_loops star_plus_without_loops)
+qed
+
+lemma root_root:
+  "root p x = root p (root p x)"
+  by (smt comp_associative comp_inf.mult_right_sub_dist_sup_right dual_order.eq_iff inf.cobounded1 inf.cobounded2 inf.orderE mult_right_isotone star.circ_loop_fixpoint star.circ_transitive_equal root_var)
+
+lemma loop_root_2:
+  assumes "acyclic (p \<sqinter> -1)"
+    and "univalent p"
+    and "injective x"
+    and "x \<le> p\<^sup>T\<^sup>+ * x"
+  shows "x = root p x"
+proof (rule antisym)
+  have 1: "x = x \<sqinter> -(-1 * x)"
+    by (metis assms(3) comp_injective_below_complement inf.orderE mult_1_left regular_one_closed)
+  have "x \<le> (p\<^sup>T \<sqinter> -1)\<^sup>+ * x \<squnion> (p \<sqinter> 1) * x"
+    by (metis assms(4) inf_commute mult_right_dist_sup one_inf_conv plus_reachable_without_loops)
+  also have "... \<le> -1 * x \<squnion> (p \<sqinter> 1) * x"
+    by (metis assms(1) conv_complement conv_dist_inf conv_isotone conv_plus_commute mult_left_isotone semiring.add_right_mono symmetric_one_closed)
+  also have "... \<le> -1 * x \<squnion> root p x"
+    using comp_isotone inf.coboundedI2 star.circ_reflexive sup_right_isotone by auto
+  finally have "x \<le> (-1 * x \<squnion> root p x) \<sqinter> -(-1 * x)"
+    using 1 inf.boundedI inf.order_iff by blast
+  also have "... \<le> root p x"
+    using inf.sup_left_divisibility by auto
+  finally show 2: "x \<le> root p x"
+    .
+  have "root p x = (p \<sqinter> 1) * x \<squnion> (p \<sqinter> 1) * (p\<^sup>T \<sqinter> -1)\<^sup>+ * x"
+    by (metis comp_associative mult_left_dist_sup star.circ_loop_fixpoint sup_commute reachable_without_loops root_var)
+  also have "... \<le> x \<squnion> (p \<sqinter> 1) * (p\<^sup>T \<sqinter> -1)\<^sup>+ * root p x"
+    using 2 by (metis coreflexive_comp_top_inf inf.cobounded2 mult_right_isotone semiring.add_mono)
+  also have "... = x"
+    by (metis assms(1,2) one_loop root_var mult_assoc semiring.mult_not_zero sup_bot_right)
+  finally show "root p x \<le> x"
+    .
+qed
+
 end
 
 context stone_relation_algebra_tarski
 begin
 
 text \<open>Two basic results about points using the Tarski rule of relation algebras\<close>
 
 lemma point_in_vector_partition:
   assumes "point x"
     and "vector y"
   shows "x \<le> -y \<or> x \<le> --y"
 proof (cases "x * x\<^sup>T \<le> -y")
   case True
   have "x \<le> x * x\<^sup>T * x"
     by (simp add: ex231c)
   also have "... \<le> -y * x"
     by (simp add: True mult_left_isotone)
   also have "... \<le> -y"
     by (metis assms(2) mult_right_isotone top.extremum vector_complement_closed)
   finally show ?thesis
     by simp
 next
   case False
   have "x \<le> x * x\<^sup>T * x"
     by (simp add: ex231c)
   also have "... \<le> --y * x"
     using False assms(1) arc_in_partition mult_left_isotone point_arc by blast
   also have "... \<le> --y"
     by (metis assms(2) mult_right_isotone top.extremum vector_complement_closed)
   finally show ?thesis
     by simp
 qed
 
 lemma point_atomic_vector:
   assumes "point x"
     and "vector y"
     and "regular y"
     and "y \<le> x"
   shows "y = x \<or> y = bot"
 proof (cases "x \<le> -y")
   case True
   thus ?thesis
     using assms(4) inf.absorb2 pseudo_complement by force
 next
   case False
   thus ?thesis
     using assms point_in_vector_partition by fastforce
 qed
 
+lemma point_in_vector_partition_2:
+  assumes "point x"
+    and "vector y"
+    and "regular y"
+    and "\<not> y \<le> -x"
+  shows "x \<le> y"
+  using assms point_in_vector_partition p_antitone_iff by fastforce
+
 text \<open>Theorem 4.3\<close>
 
 lemma distinct_points:
   assumes "point x"
     and "point y"
     and "x \<noteq> y"
   shows "x \<sqinter> y = bot"
   by (metis assms antisym comp_bijective_complement inf.sup_monoid.add_commute mult_left_one pseudo_complement regular_one_closed point_in_vector_partition)
 
 text \<open>Back and von Wright's array independence requirements \cite{BackWright1998}\<close>
 
-lemma put_get_different:
-  assumes "point y" "point w" "w \<noteq> y"
+lemma put_get_different_vector:
+  assumes "vector y" "vector w" "w \<le> -y"
   shows "(x[y\<longmapsto>z])[[w]] = x[[w]]"
 proof -
   have "(x[y\<longmapsto>z])[[w]] = (y\<^sup>T \<sqinter> z) * w \<squnion> (-y\<^sup>T \<sqinter> x\<^sup>T) * w"
     by (simp add: conv_complement conv_dist_inf conv_dist_sup mult_right_dist_sup)
   also have "... = z * (w \<sqinter> y) \<squnion> x\<^sup>T * (w \<sqinter> -y)"
     by (metis assms(1) conv_complement covector_inf_comp_3 inf_commute vector_complement_closed)
+  also have "... = z * (w \<sqinter> y) \<squnion> x\<^sup>T * w"
+    by (simp add: assms(3) inf.absorb1)
+  also have "... = z * bot \<squnion> x\<^sup>T * w"
+    by (metis assms(3) comp_inf.semiring.mult_zero_right inf.absorb1 inf.sup_monoid.add_assoc p_inf)
   also have "... = x\<^sup>T * w"
-  proof -
-    have 1: "w \<sqinter> y = bot"
-      using assms distinct_points by simp
-    hence "w \<le> -y"
-      using pseudo_complement by simp
-    thus ?thesis
-      using 1 by (simp add: inf.absorb1)
-  qed
+    by simp
   finally show ?thesis
     .
 qed
 
-lemma put_put_different:
-  assumes "point y" "point v" "v \<noteq> y"
+lemma put_get_different:
+  assumes "point y" "point w" "w \<noteq> y"
+  shows "(x[y\<longmapsto>z])[[w]] = x[[w]]"
+proof -
+  have "w \<sqinter> y = bot"
+    using assms distinct_points by simp
+  hence "w \<le> -y"
+    using pseudo_complement by simp
+  thus ?thesis
+    by (simp add: assms(1) assms(2) put_get_different_vector)
+qed
+
+lemma put_put_different_vector:
+  assumes "vector y" "vector v" "v \<sqinter> y = bot"
   shows "(x[y\<longmapsto>z])[v\<longmapsto>w] = (x[v\<longmapsto>w])[y\<longmapsto>z]"
 proof -
   have "(x[y\<longmapsto>z])[v\<longmapsto>w] = (v \<sqinter> w\<^sup>T) \<squnion> (-v \<sqinter> y \<sqinter> z\<^sup>T) \<squnion> (-v \<sqinter> -y \<sqinter> x)"
     by (simp add: comp_inf.semiring.distrib_left inf_assoc sup_assoc)
   also have "... = (v \<sqinter> w\<^sup>T) \<squnion> (y \<sqinter> z\<^sup>T) \<squnion> (-v \<sqinter> -y \<sqinter> x)"
-    using assms distinct_points pseudo_complement inf.absorb2 by simp
+    by (metis assms(3) inf_commute inf_import_p p_inf selection_closed_id)
   also have "... = (y \<sqinter> z\<^sup>T) \<squnion> (v \<sqinter> w\<^sup>T) \<squnion> (-y \<sqinter> -v \<sqinter> x)"
     by (simp add: inf_commute sup_commute)
   also have "... = (y \<sqinter> z\<^sup>T) \<squnion> (-y \<sqinter> v \<sqinter> w\<^sup>T) \<squnion> (-y \<sqinter> -v \<sqinter> x)"
     using assms distinct_points pseudo_complement inf.absorb2 by simp
   also have "... = (x[v\<longmapsto>w])[y\<longmapsto>z]"
     by (simp add: comp_inf.semiring.distrib_left inf_assoc sup_assoc)
   finally show ?thesis
     .
 qed
 
+lemma put_put_different:
+  assumes "point y" "point v" "v \<noteq> y"
+  shows "(x[y\<longmapsto>z])[v\<longmapsto>w] = (x[v\<longmapsto>w])[y\<longmapsto>z]"
+  using assms distinct_points put_put_different_vector by blast
+
 end
 
 section \<open>Verifying Operations on Disjoint-Set Forests\<close>
 
 text \<open>
 In this section we verify the make-set, find-set and union-sets operations of disjoint-set forests.
 We start by introducing syntax for updating arrays in programs.
 Updating the value at a given array index means updating the whole array.
 \<close>
 
 syntax
   "_rel_update" :: "idt \<Rightarrow> 'a \<Rightarrow> 'a \<Rightarrow> 'b com" ("(2_[_] :=/ _)" [70, 65, 65] 61)
 
 translations
   "x[y] := z" => "(x := (y \<sqinter> z\<^sup>T) \<squnion> (CONST uminus y \<sqinter> x))"
 
 text \<open>
 The finiteness requirement in the following class is used for proving that the operations terminate.
 \<close>
 
 class finite_regular_p_algebra = p_algebra +
   assumes finite_regular: "finite { x . regular x }"
 
 class stone_kleene_relation_algebra_tarski = stone_kleene_relation_algebra + stone_relation_algebra_tarski
 
 class stone_kleene_relation_algebra_tarski_finite_regular = stone_kleene_relation_algebra_tarski + finite_regular_p_algebra
 begin
 
 subsection \<open>Make-Set\<close>
 
 text \<open>
 We prove two correctness results about make-set.
 The first shows that the forest changes only to the extent of making one node the root of a tree.
 The second result adds that only singleton sets are created.
 \<close>
 
 definition "make_set_postcondition p x p0 \<equiv> x \<sqinter> p = x * x\<^sup>T \<and> -x \<sqinter> p = -x \<sqinter> p0"
 
 theorem make_set:
   "VARS p
   [ point x \<and> p0 = p ]
   p[x] := x
   [ make_set_postcondition p x p0 ]"
   apply vcg_tc_simp
   by (simp add: make_set_postcondition_def inf_sup_distrib1 inf_assoc[THEN sym] vector_covector[THEN sym])
 
 theorem make_set_2:
   "VARS p
   [ point x \<and> p0 = p \<and> p \<le> 1 ]
   p[x] := x
   [ make_set_postcondition p x p0 \<and> p \<le> 1 ]"
 proof vcg_tc
   fix p
   assume 1: "point x \<and> p0 = p \<and> p \<le> 1"
   show "make_set_postcondition (p[x\<longmapsto>x]) x p0 \<and> p[x\<longmapsto>x] \<le> 1"
   proof (rule conjI)
     show "make_set_postcondition (p[x\<longmapsto>x]) x p0"
       using 1 by (simp add: make_set_postcondition_def inf_sup_distrib1 inf_assoc[THEN sym] vector_covector[THEN sym])
     show "p[x\<longmapsto>x] \<le> 1"
       using 1 by (metis coreflexive_sup_closed dual_order.trans inf.cobounded2 vector_covector)
   qed
 qed
 
 text \<open>
 The above total-correctness proof allows us to extract a function, which can be used in other implementations below.
 This is a technique of \cite{Guttmann2018c}.
 \<close>
 
 lemma make_set_exists:
   "point x \<Longrightarrow> \<exists>p' . make_set_postcondition p' x p"
   using tc_extract_function make_set by blast
 
 definition "make_set p x \<equiv> (SOME p' . make_set_postcondition p' x p)"
 
 lemma make_set_function:
   assumes "point x"
     and "p' = make_set p x"
   shows "make_set_postcondition p' x p"
 proof -
   let ?P = "\<lambda>p' . make_set_postcondition p' x p"
   have "?P (SOME z . ?P z)"
     using assms(1) make_set_exists by (meson someI)
   thus ?thesis
     using assms(2) make_set_def by auto
 qed
 
 subsection \<open>Find-Set\<close>
 
 text \<open>
 Disjoint-set forests are represented by their parent mapping.
 It is a forest except each root of a component tree points to itself.
 
 We prove that find-set returns the root of the component tree of the given node.
 \<close>
 
 abbreviation "disjoint_set_forest p \<equiv> mapping p \<and> acyclic (p \<sqinter> -1)"
 
 definition "find_set_precondition p x \<equiv> disjoint_set_forest p \<and> point x"
 definition "find_set_invariant p x y \<equiv> find_set_precondition p x \<and> point y \<and> y \<le> p\<^sup>T\<^sup>\<star> * x"
 definition "find_set_postcondition p x y \<equiv> point y \<and> y = root p x"
 
 lemma find_set_1:
   "find_set_precondition p x \<Longrightarrow> find_set_invariant p x x"
   apply (unfold find_set_invariant_def)
   using mult_left_isotone star.circ_reflexive find_set_precondition_def by fastforce
 
 lemma find_set_2:
   "find_set_invariant p x y \<and> y \<noteq> p[[y]] \<Longrightarrow> find_set_invariant p x (p[[y]]) \<and> card { z . regular z \<and> z \<le> p\<^sup>T\<^sup>\<star> * (p[[y]]) } < card { z . regular z \<and> z \<le> p\<^sup>T\<^sup>\<star> * y }"
 proof -
   let ?s = "{ z . regular z \<and> z \<le> p\<^sup>T\<^sup>\<star> * y }"
   let ?t = "{ z . regular z \<and> z \<le> p\<^sup>T\<^sup>\<star> * (p[[y]]) }"
   assume 1: "find_set_invariant p x y \<and> y \<noteq> p[[y]]"
   have 2: "point (p[[y]])"
     using 1 read_point find_set_invariant_def find_set_precondition_def by simp
   show "find_set_invariant p x (p[[y]]) \<and> card ?t < card ?s"
   proof (unfold find_set_invariant_def, intro conjI)
     show "find_set_precondition p x"
       using 1 find_set_invariant_def by simp
     show "vector (p[[y]])"
       using 2 by simp
     show "injective (p[[y]])"
       using 2 by simp
     show "surjective (p[[y]])"
       using 2 by simp
     show "p[[y]] \<le> p\<^sup>T\<^sup>\<star> * x"
       using 1 by (metis (hide_lams) find_set_invariant_def comp_associative comp_isotone star.circ_increasing star.circ_transitive_equal)
     show "card ?t < card ?s"
     proof -
       have 3: "(p\<^sup>T \<sqinter> -1) * (p\<^sup>T \<sqinter> -1)\<^sup>+ * y \<le> (p\<^sup>T \<sqinter> -1)\<^sup>+ * y"
         by (simp add: mult_left_isotone mult_right_isotone star.left_plus_below_circ)
       have "p[[y]] = (p\<^sup>T \<sqinter> 1) * y \<squnion> (p\<^sup>T \<sqinter> -1) * y"
         by (metis maddux_3_11_pp mult_right_dist_sup regular_one_closed)
       also have "... \<le> ((p[[y]]) \<sqinter> y) \<squnion> (p\<^sup>T \<sqinter> -1) * y"
         by (metis comp_left_subdist_inf mult_1_left semiring.add_right_mono)
       also have "... = (p\<^sup>T \<sqinter> -1) * y"
         using 1 2 find_set_invariant_def distinct_points by auto
       finally have 4: "(p\<^sup>T \<sqinter> -1)\<^sup>\<star> * (p[[y]]) \<le> (p\<^sup>T \<sqinter> -1)\<^sup>+ * y"
         using 3 by (metis inf.antisym_conv inf.eq_refl inf_le1 mult_left_isotone star_plus mult_assoc)
       hence "p\<^sup>T\<^sup>\<star> * (p[[y]]) \<le> p\<^sup>T\<^sup>\<star> * y"
         by (metis mult_isotone order_refl star.left_plus_below_circ star_plus mult_assoc)
       hence 5: "?t \<subseteq> ?s"
         using order_trans by auto
       have 6: "y \<in> ?s"
         using 1 find_set_invariant_def bijective_regular mult_left_isotone star.circ_reflexive by fastforce
       have 7: "\<not> y \<in> ?t"
       proof
         assume "y \<in> ?t"
         hence "y \<le> (p\<^sup>T \<sqinter> -1)\<^sup>+ * y"
           using 4 by (metis reachable_without_loops mem_Collect_eq order_trans)
         hence "y * y\<^sup>T \<le> (p\<^sup>T \<sqinter> -1)\<^sup>+"
           using 1 find_set_invariant_def shunt_bijective by simp
         also have "... \<le> -1"
           using 1 by (metis (mono_tags, lifting) find_set_invariant_def find_set_precondition_def conv_dist_comp conv_dist_inf conv_isotone conv_star_commute equivalence_one_closed star.circ_plus_same symmetric_complement_closed)
         finally have "y \<le> -y"
           using schroeder_4_p by auto
         thus False
           using 1 by (metis find_set_invariant_def comp_inf.coreflexive_idempotent conv_complement covector_vector_comp inf.absorb1 inf.sup_monoid.add_commute pseudo_complement surjective_conv_total top.extremum vector_top_closed regular_closed_top)
       qed
       show "card ?t < card ?s"
         apply (rule psubset_card_mono)
         subgoal using finite_regular by simp
         subgoal using 5 6 7 by auto
         done
     qed
   qed
 qed
 
 lemma find_set_3:
   "find_set_invariant p x y \<and> y = p[[y]] \<Longrightarrow> find_set_postcondition p x y"
 proof -
   assume 1: "find_set_invariant p x y \<and> y = p[[y]]"
   show "find_set_postcondition p x y"
   proof (unfold find_set_postcondition_def, rule conjI)
     show "point y"
       using 1 find_set_invariant_def by simp
     show "y = root p x"
     proof (rule antisym)
       have "y * y\<^sup>T \<le> p"
         using 1 by (metis find_set_invariant_def find_set_precondition_def shunt_bijective shunt_mapping top_right_mult_increasing)
       hence "y * y\<^sup>T \<le> p \<sqinter> 1"
         using 1 find_set_invariant_def le_infI by blast
       hence "y \<le> (p \<sqinter> 1) * top"
         using 1 by (metis find_set_invariant_def order_lesseq_imp shunt_bijective top_right_mult_increasing mult_assoc)
       thus "y \<le> root p x"
         using 1 find_set_invariant_def by simp
     next
       have 2: "x \<le> p\<^sup>\<star> * y"
         using 1 find_set_invariant_def find_set_precondition_def bijective_reverse conv_star_commute by auto
       have "p\<^sup>T * p\<^sup>\<star> * y = p\<^sup>T * p * p\<^sup>\<star> * y \<squnion> (p[[y]])"
         by (metis comp_associative mult_left_dist_sup star.circ_loop_fixpoint)
       also have "... \<le> p\<^sup>\<star> * y \<squnion> y"
         using 1 by (metis find_set_invariant_def find_set_precondition_def comp_isotone mult_left_sub_dist_sup semiring.add_right_mono star.circ_back_loop_fixpoint star.circ_circ_mult star.circ_top star.circ_transitive_equal star_involutive star_one)
       also have "... = p\<^sup>\<star> * y"
         by (metis star.circ_loop_fixpoint sup.left_idem sup_commute)
       finally have 3: "p\<^sup>T\<^sup>\<star> * x \<le> p\<^sup>\<star> * y"
         using 2 by (simp add: comp_associative star_left_induct)
       have "p * y \<sqinter> (p \<sqinter> 1) * top = (p \<sqinter> 1) * p * y"
         using comp_associative coreflexive_comp_top_inf inf_commute by auto
       also have "... \<le> p\<^sup>T * p * y"
         by (metis inf.cobounded2 inf.sup_monoid.add_commute mult_left_isotone one_inf_conv)
       also have "... \<le> y"
         using 1 find_set_invariant_def find_set_precondition_def mult_left_isotone by fastforce
       finally have 4: "p * y \<le> y \<squnion> -((p \<sqinter> 1) * top)"
         using 1 by (metis find_set_invariant_def shunting_p bijective_regular)
       have "p\<^sup>T * (p \<sqinter> 1) \<le> p\<^sup>T \<sqinter> 1"
         using 1 by (metis find_set_invariant_def find_set_precondition_def N_top comp_isotone coreflexive_idempotent inf.cobounded2 inf.sup_monoid.add_commute inf_assoc one_inf_conv shunt_mapping)
       hence "p\<^sup>T * (p \<sqinter> 1) * top \<le> (p \<sqinter> 1) * top"
         using inf_commute mult_isotone one_inf_conv by auto
       hence "p * -((p \<sqinter> 1) * top) \<le> -((p \<sqinter> 1) * top)"
         by (metis comp_associative inf.sup_monoid.add_commute p_antitone p_antitone_iff schroeder_3_p)
       hence "p * y \<squnion> p * -((p \<sqinter> 1) * top) \<le> y \<squnion> -((p \<sqinter> 1) * top)"
         using 4 dual_order.trans le_supI sup_ge2 by blast
       hence "p * (y \<squnion> -((p \<sqinter> 1) * top)) \<le> y \<squnion> -((p \<sqinter> 1) * top)"
         by (simp add: mult_left_dist_sup)
       hence "p\<^sup>\<star> * y \<le> y \<squnion> -((p \<sqinter> 1) * top)"
         by (simp add: star_left_induct)
       hence "p\<^sup>T\<^sup>\<star> * x \<le> y \<squnion> -((p \<sqinter> 1) * top)"
         using 3 dual_order.trans by blast
       thus "root p x \<le> y"
         using 1 by (metis find_set_invariant_def shunting_p bijective_regular)
     qed
   qed
 qed
 
 theorem find_set:
   "VARS y
   [ find_set_precondition p x ]
   y := x;
   WHILE y \<noteq> p[[y]]
     INV { find_set_invariant p x y }
     VAR { card { z . regular z \<and> z \<le> p\<^sup>T\<^sup>\<star> * y } }
      DO y := p[[y]]
      OD
   [ find_set_postcondition p x y ]"
   apply vcg_tc_simp
     apply (fact find_set_1)
    apply (fact find_set_2)
   by (fact find_set_3)
 
 lemma find_set_exists:
   "find_set_precondition p x \<Longrightarrow> \<exists>y . find_set_postcondition p x y"
   using tc_extract_function find_set by blast
 
 text \<open>
 The root of a component tree is a point, that is, represents a singleton set of nodes.
 This could be proved from the definitions using Kleene-relation algebraic calculations.
 But they can be avoided because the property directly follows from the postcondition of the previous correctness proof.
 The corresponding algorithm shows how to obtain the root.
 We therefore have an essentially constructive proof of the following result.
 \<close>
 
 text \<open>Theorem 3.3\<close>
 
 lemma root_point:
   "disjoint_set_forest p \<Longrightarrow> point x \<Longrightarrow> point (root p x)"
   using find_set_exists find_set_precondition_def find_set_postcondition_def by simp
 
 definition "find_set p x \<equiv> (SOME y . find_set_postcondition p x y)"
 
 lemma find_set_function:
   assumes "find_set_precondition p x"
     and "y = find_set p x"
   shows "find_set_postcondition p x y"
   by (metis assms find_set_def find_set_exists someI)
 
 subsection \<open>Path Compression\<close>
 
 text \<open>
 The path-compression technique is frequently implemented in recursive implementations of find-set 
 modifying the tree on the way out from recursive calls. Here we implement it using a second while-loop, 
 which iterates over the same path to the root and changes edges to point to the root of the component, 
 which is known after the while-loop in find-set completes. We prove that path compression preserves 
 the equivalence-relational semantics of the disjoint-set forest and also preserves the roots of the 
-component trees.
+component trees. Additionally we prove the exact effect of path compression.
 \<close>
 
 definition "path_compression_precondition p x y \<equiv> disjoint_set_forest p \<and> point x \<and> point y \<and> y = root p x"
 definition "path_compression_invariant p x y p0 w \<equiv> 
   path_compression_precondition p x y \<and> point w \<and> y \<le> p\<^sup>T\<^sup>\<star> * w \<and> 
-  (w \<noteq> x \<longrightarrow> p[[x]] = y \<and> y \<noteq> x \<and> p\<^sup>T\<^sup>+ * w \<le> -x) \<and> p \<sqinter> 1 = p0 \<sqinter> 1 \<and> fc p = fc p0"
+  (w \<noteq> x \<longrightarrow> p[[x]] = y \<and> y \<noteq> x \<and> p\<^sup>T\<^sup>+ * w \<le> -x) \<and> p \<sqinter> 1 = p0 \<sqinter> 1 \<and> fc p = fc p0 \<and>
+  root p w = y \<and> (w \<noteq> y \<longrightarrow> p[[w]] \<noteq> w \<and> p\<^sup>T\<^sup>+ * w \<le> -w) \<and> p[[w]] = p0[[w]] \<and> p0[p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * w)\<longmapsto>y] = p \<and>
+  disjoint_set_forest p0 \<and> y = root p0 x \<and> w \<le> p0\<^sup>T\<^sup>\<star> * x"
 definition "path_compression_postcondition p x y p0 \<equiv> 
-  path_compression_precondition p x y \<and> p \<sqinter> 1 = p0 \<sqinter> 1 \<and> fc p = fc p0"
+  path_compression_precondition p x y \<and> p \<sqinter> 1 = p0 \<sqinter> 1 \<and> fc p = fc p0 \<and>
+  p0[p0\<^sup>T\<^sup>\<star> * x\<longmapsto>y] = p"
+
+text \<open>
+We first consider a variant that achieves the effect as a single update.
+The parents of all nodes reachable from x are simultaneously updated to the root of the component of x.
+\<close>
+
+lemma path_compression_exact:
+  assumes "path_compression_precondition p0 x y"
+    and "p0[p0\<^sup>T\<^sup>\<star> * x\<longmapsto>y] = p"
+  shows "p \<sqinter> 1 = p0 \<sqinter> 1" "fc p = fc p0"
+proof -
+  have a1: "disjoint_set_forest p0" and a2: "point x" and a3: "point y" and a4: "y = root p0 x"
+    using path_compression_precondition_def assms(1) by auto
+  have 1: "regular (p0\<^sup>T\<^sup>\<star> * x)"
+    using a1 a2 bijective_regular mapping_regular regular_closed_star regular_conv_closed regular_mult_closed by auto
+  have "p \<sqinter> 1 = (p0\<^sup>T\<^sup>\<star> * x \<sqinter> y\<^sup>T \<sqinter> 1) \<squnion> (-(p0\<^sup>T\<^sup>\<star> * x) \<sqinter> p0 \<sqinter> 1)"
+    using assms(2) inf_sup_distrib2 by auto
+  also have "... = (p0\<^sup>T\<^sup>\<star> * x \<sqinter> p0 \<sqinter> 1) \<squnion> (-(p0\<^sup>T\<^sup>\<star> * x) \<sqinter> p0 \<sqinter> 1)"
+  proof -
+    have "p0\<^sup>T\<^sup>\<star> * x \<sqinter> y\<^sup>T \<sqinter> 1 = p0\<^sup>T\<^sup>\<star> * x \<sqinter> p0 \<sqinter> 1"
+    proof (rule antisym)
+      have "(p0 \<sqinter> 1) * p0\<^sup>T\<^sup>\<star> * x \<sqinter> 1 \<le> p0"
+        by (smt coreflexive_comp_top_inf_one inf.absorb_iff2 inf.cobounded2 inf.sup_monoid.add_assoc root_var)
+      hence "p0\<^sup>T\<^sup>\<star> * x \<sqinter> y\<^sup>T \<sqinter> 1 \<le> p0"
+        by (metis inf_le1 a4 conv_dist_inf coreflexive_symmetric inf.absorb2 inf.cobounded2 inf.sup_monoid.add_assoc root_var symmetric_one_closed)
+      thus "p0\<^sup>T\<^sup>\<star> * x \<sqinter> y\<^sup>T \<sqinter> 1 \<le> p0\<^sup>T\<^sup>\<star> * x \<sqinter> p0 \<sqinter> 1"
+        by (meson inf.le_sup_iff order.refl)
+      have "p0\<^sup>T\<^sup>\<star> * x \<sqinter> p0 \<sqinter> 1 \<le> y"
+        by (metis a4 coreflexive_comp_top_inf_one inf.cobounded1 inf_assoc inf_le2)
+      thus "p0\<^sup>T\<^sup>\<star> * x \<sqinter> p0 \<sqinter> 1 \<le> p0\<^sup>T\<^sup>\<star> * x \<sqinter> y\<^sup>T \<sqinter> 1"
+        by (smt conv_dist_inf coreflexive_symmetric inf.absorb_iff2 inf.cobounded2 inf.sup_monoid.add_assoc)
+    qed
+    thus ?thesis
+      by simp
+  qed
+  also have "... = p0 \<sqinter> 1"
+    using 1 by (metis inf.sup_monoid.add_commute inf_sup_distrib1 maddux_3_11_pp)
+  finally show "p \<sqinter> 1 = p0 \<sqinter> 1"
+    .
+  show  "fc p = fc p0"
+  proof (rule antisym)
+    have 2: "univalent (p0[p0\<^sup>T\<^sup>\<star> * x\<longmapsto>y])"
+      by (simp add: a1 a2 a3 update_univalent mult_assoc)
+    have 3: "-(p0\<^sup>T\<^sup>\<star> * x) \<sqinter> p0 \<le> (p0[p0\<^sup>T\<^sup>\<star> * x\<longmapsto>y])\<^sup>\<star> * (p0[p0\<^sup>T\<^sup>\<star> * x\<longmapsto>y])\<^sup>T\<^sup>\<star>"
+      using fc_increasing inf.order_trans sup.cobounded2 by blast
+    have "p0\<^sup>T\<^sup>\<star> * x \<sqinter> p0 \<le> (p0\<^sup>T\<^sup>\<star> \<sqinter> p0 * x\<^sup>T) * (x \<sqinter> p0\<^sup>\<star> * p0)"
+      by (metis conv_involutive conv_star_commute dedekind)
+    also have "... \<le> p0\<^sup>T\<^sup>\<star> * x \<sqinter> p0 * x\<^sup>T * p0\<^sup>\<star> * p0"
+      by (metis comp_associative inf.boundedI inf.cobounded2 inf_le1 mult_isotone)
+    also have "... \<le> p0\<^sup>T\<^sup>\<star> * x \<sqinter> top * x\<^sup>T * p0\<^sup>\<star>"
+      using comp_associative comp_inf.mult_right_isotone mult_isotone star.right_plus_below_circ by auto
+    also have "... = p0\<^sup>T\<^sup>\<star> * x * x\<^sup>T * p0\<^sup>\<star>"
+      by (metis a2 symmetric_top_closed vector_covector vector_inf_comp vector_mult_closed)
+    also have "... \<le> (p0\<^sup>T\<^sup>\<star> * x * y\<^sup>T) * (y * x\<^sup>T * p0\<^sup>\<star>)"
+      by (metis a3 antisym comp_inf.top_right_mult_increasing conv_involutive dedekind_1 inf.sup_left_divisibility inf.sup_monoid.add_commute mult_right_isotone surjective_conv_total mult_assoc)
+    also have "... = (p0\<^sup>T\<^sup>\<star> * x \<sqinter> y\<^sup>T) * (y \<sqinter> x\<^sup>T * p0\<^sup>\<star>)"
+      by (metis a2 a3 vector_covector vector_inf_comp vector_mult_closed)
+    also have "... = (p0\<^sup>T\<^sup>\<star> * x \<sqinter> y\<^sup>T) * (p0\<^sup>T\<^sup>\<star> * x \<sqinter> y\<^sup>T)\<^sup>T"
+      by (simp add: conv_dist_comp conv_dist_inf conv_star_commute inf_commute)
+    also have "... \<le> (p0[p0\<^sup>T\<^sup>\<star> * x\<longmapsto>y])\<^sup>\<star> * (p0[p0\<^sup>T\<^sup>\<star> * x\<longmapsto>y])\<^sup>T\<^sup>\<star>"
+      by (meson conv_isotone dual_order.trans mult_isotone star.circ_increasing sup.cobounded1)
+    finally have "p0\<^sup>T\<^sup>\<star> * x \<sqinter> p0 \<le> (p0[p0\<^sup>T\<^sup>\<star> * x\<longmapsto>y])\<^sup>\<star> * (p0[p0\<^sup>T\<^sup>\<star> * x\<longmapsto>y])\<^sup>T\<^sup>\<star>"
+      .
+    hence "(p0\<^sup>T\<^sup>\<star> * x \<sqinter> p0) \<squnion> (-(p0\<^sup>T\<^sup>\<star> * x) \<sqinter> p0) \<le> (p0[p0\<^sup>T\<^sup>\<star> * x\<longmapsto>y])\<^sup>\<star> * (p0[p0\<^sup>T\<^sup>\<star> * x\<longmapsto>y])\<^sup>T\<^sup>\<star>"
+      using 3 le_supI by blast
+    hence "p0 \<le> (p0[p0\<^sup>T\<^sup>\<star> * x\<longmapsto>y])\<^sup>\<star> * (p0[p0\<^sup>T\<^sup>\<star> * x\<longmapsto>y])\<^sup>T\<^sup>\<star>"
+      using 1 by (metis inf_commute maddux_3_11_pp)
+    hence "fc p0 \<le> (p0[p0\<^sup>T\<^sup>\<star> * x\<longmapsto>y])\<^sup>\<star> * (p0[p0\<^sup>T\<^sup>\<star> * x\<longmapsto>y])\<^sup>T\<^sup>\<star>"
+      using 2 fc_idempotent fc_isotone by fastforce
+    thus "fc p0 \<le> fc p"
+      by (simp add: assms(2))
+    have "((p0\<^sup>T\<^sup>\<star> * x \<sqinter> y\<^sup>T) \<squnion> (-(p0\<^sup>T\<^sup>\<star> * x) \<sqinter> p0))\<^sup>\<star> = (-(p0\<^sup>T\<^sup>\<star> * x) \<sqinter> p0)\<^sup>\<star> * ((p0\<^sup>T\<^sup>\<star> * x \<sqinter> y\<^sup>T) \<squnion> 1)"
+    proof (rule star_sup_2)
+      have 4: "transitive (p0\<^sup>T\<^sup>\<star> * x)"
+        using a2 comp_associative mult_right_isotone rectangle_star_rectangle by auto
+      have "transitive (y\<^sup>T)"
+        by (metis a3 conv_dist_comp inf.eq_refl mult_assoc)
+      thus "transitive (p0\<^sup>T\<^sup>\<star> * x \<sqinter> y\<^sup>T)"
+        using 4 transitive_inf_closed by auto
+      have 5: "p0\<^sup>T\<^sup>\<star> * x * (-(p0\<^sup>T\<^sup>\<star> * x) \<sqinter> p0) \<le> p0\<^sup>T\<^sup>\<star> * x"
+        by (metis a2 mult_right_isotone top_greatest mult_assoc)
+      have "(-(p0\<^sup>T\<^sup>\<star> * x) \<sqinter> p0)\<^sup>T * y \<le> p0\<^sup>T * y"
+        by (simp add: conv_dist_inf mult_left_isotone)
+      also have "... \<le> y"
+        using a1 a4 root_successor_loop by auto
+      finally have "y\<^sup>T * (-(p0\<^sup>T\<^sup>\<star> * x) \<sqinter> p0) \<le> y\<^sup>T"
+        using conv_dist_comp conv_isotone by fastforce
+      thus "(p0\<^sup>T\<^sup>\<star> * x \<sqinter> y\<^sup>T) * (-(p0\<^sup>T\<^sup>\<star> * x) \<sqinter> p0) \<le> p0\<^sup>T\<^sup>\<star> * x \<sqinter> y\<^sup>T"
+        using 5 comp_left_subdist_inf inf_mono order_trans by blast
+    qed
+    hence "p\<^sup>\<star> = (-(p0\<^sup>T\<^sup>\<star> * x) \<sqinter> p0)\<^sup>\<star> * ((p0\<^sup>T\<^sup>\<star> * x \<sqinter> y\<^sup>T) \<squnion> 1)"
+      by (simp add: assms(2))
+    also have "... \<le> p0\<^sup>\<star> * ((p0\<^sup>T\<^sup>\<star> * x \<sqinter> y\<^sup>T) \<squnion> 1)"
+      by (simp add: mult_left_isotone star_isotone)
+    also have "... = p0\<^sup>\<star> * (p0\<^sup>T\<^sup>\<star> * x * y\<^sup>T \<squnion> 1)"
+      by (simp add: a2 a3 vector_covector vector_mult_closed)
+    also have "... = p0\<^sup>\<star> * (p0\<^sup>T\<^sup>\<star> * (x * x\<^sup>T) * p0\<^sup>\<star> * (p0 \<sqinter> 1) \<squnion> 1)"
+      by (metis a4 coreflexive_symmetric inf.cobounded2 root_var comp_associative conv_dist_comp conv_involutive conv_star_commute)
+    also have "... \<le> p0\<^sup>\<star> * (p0\<^sup>T\<^sup>\<star> * 1 * p0\<^sup>\<star> * (p0 \<sqinter> 1) \<squnion> 1)"
+      by (metis a2 mult_left_isotone mult_right_isotone semiring.add_left_mono sup_commute)
+    also have "... = p0\<^sup>\<star> * (p0\<^sup>T\<^sup>\<star> * (p0 \<sqinter> 1) \<squnion> p0\<^sup>\<star> * (p0 \<sqinter> 1) \<squnion> 1)"
+      by (simp add: a1 cancel_separate_eq mult_right_dist_sup)
+    also have "... = p0\<^sup>\<star> * ((p0 \<sqinter> 1) \<squnion> p0\<^sup>\<star> * (p0 \<sqinter> 1) \<squnion> 1)"
+      by (smt univalent_root_successors a1 conv_dist_comp conv_dist_inf coreflexive_idempotent coreflexive_symmetric inf.cobounded2 injective_codomain loop_root root_transitive_successor_loop symmetric_one_closed)
+    also have "... = p0\<^sup>\<star> * (p0\<^sup>\<star> * (p0 \<sqinter> 1) \<squnion> 1)"
+      by (metis inf.sup_left_divisibility inf_commute sup.left_idem sup_commute sup_relative_same_increasing)
+    also have "... \<le> p0\<^sup>\<star> * p0\<^sup>\<star>"
+      by (metis inf.cobounded2 inf_commute order.refl order_lesseq_imp star.circ_mult_upper_bound star.circ_reflexive star.circ_transitive_equal sup.boundedI sup_monoid.add_commute)
+    also have "... = p0\<^sup>\<star>"
+      by (simp add: star.circ_transitive_equal)
+    finally show "fc p \<le> fc p0"
+      by (metis conv_order conv_star_commute mult_isotone)
+  qed
+qed
+
+lemma update_acyclic_6:
+  assumes "disjoint_set_forest p"
+    and "point x"
+  shows "acyclic ((p[p\<^sup>T\<^sup>\<star>*x\<longmapsto>root p x]) \<sqinter> -1)"
+  using assms root_point root_successor_loop update_acyclic_2 by auto
+
+theorem path_compression_assign:
+  "VARS p t w
+  [ path_compression_precondition p x y \<and> p0 = p ]
+  p[p\<^sup>T\<^sup>\<star> * x] := y
+  [ path_compression_postcondition p x y p0 ]"
+  apply vcg_tc_simp
+  apply (unfold path_compression_precondition_def path_compression_postcondition_def)
+  apply (intro conjI)
+  subgoal using update_univalent mult_assoc by auto
+  subgoal using bijective_regular mapping_regular regular_closed_star regular_conv_closed regular_mult_closed update_mapping mult_assoc by auto
+  subgoal using update_acyclic_6 by blast
+  subgoal by blast
+  subgoal by blast
+  subgoal by blast
+  subgoal by blast
+  subgoal by blast
+  subgoal by blast
+  subgoal by (smt same_root path_compression_exact path_compression_precondition_def update_univalent vector_mult_closed)
+  subgoal using path_compression_exact(1) path_compression_precondition_def by blast
+  subgoal using path_compression_exact(2) path_compression_precondition_def by blast
+  by blast
+
+text \<open>
+We next look at implementing these updates using a loop.
+\<close>
+
+lemma path_compression_1a:
+  assumes "point x"
+    and "disjoint_set_forest p"
+    and "x \<noteq> root p x"
+  shows "p\<^sup>T\<^sup>+ * x \<le> - x"
+  by (meson assms bijective_regular mapping_regular regular_closed_star regular_conv_closed regular_mult_closed vector_mult_closed point_in_vector_partition_2 loop_root_2)
+
+lemma path_compression_1b:
+  "x \<le> p\<^sup>T\<^sup>\<star> * x"
+  using mult_left_isotone star.circ_reflexive by fastforce
 
 lemma path_compression_1:
   "path_compression_precondition p x y \<Longrightarrow> path_compression_invariant p x y p x"
-  using path_compression_invariant_def path_compression_precondition_def by auto
+  using path_compression_invariant_def path_compression_precondition_def loop_root path_compression_1a path_compression_1b by auto
 
 lemma path_compression_2:
   "path_compression_invariant p x y p0 w \<and> y \<noteq> p[[w]] \<Longrightarrow> path_compression_invariant (p[w\<longmapsto>y]) x y p0 (p[[w]]) \<and> card { z . regular z \<and> z \<le> (p[w\<longmapsto>y])\<^sup>T\<^sup>\<star> * (p[[w]]) } < card { z . regular z \<and> z \<le> p\<^sup>T\<^sup>\<star> * w }"
 proof -
   let ?p = "p[w\<longmapsto>y]"
   let ?s = "{ z . regular z \<and> z \<le> p\<^sup>T\<^sup>\<star> * w }"
   let ?t = "{ z . regular z \<and> z \<le> ?p\<^sup>T\<^sup>\<star> * (p[[w]]) }"
   assume 1: "path_compression_invariant p x y p0 w \<and> y \<noteq> p[[w]]"
-  hence 2: "point (p[[w]])"
-    by (simp add: path_compression_invariant_def path_compression_precondition_def read_point)
+  have i1: "disjoint_set_forest p" and i2: "point x" and i3: "point y" and i4: "y = root p x"
+    using 1 path_compression_invariant_def path_compression_precondition_def by meson+
+  have i5: "point w" and i6: "y \<le> p\<^sup>T\<^sup>\<star> * w"
+    and i7: "w \<noteq> x \<longrightarrow> p[[x]] = y \<and> y \<noteq> x \<and> p\<^sup>T\<^sup>+ * w \<le> -x" and i8: "p \<sqinter> 1 = p0 \<sqinter> 1" and i9: "fc p = fc p0"
+    and i10: "root p w = y" and i11: "w \<noteq> y \<longrightarrow> p[[w]] \<noteq> w" and i12: "p[[w]] = p0[[w]]" and i13: "p0[p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * w)\<longmapsto>y] = p"
+    using 1 path_compression_invariant_def by blast+
+  have i14: "disjoint_set_forest p0" and i15: "y = root p0 x" and i16: "w \<le> p0\<^sup>T\<^sup>\<star> * x"
+    using 1 path_compression_invariant_def by auto
+  have 2: "point (p[[w]])"
+    using i1 i5 read_point by blast
   show "path_compression_invariant ?p x y p0 (p[[w]]) \<and> card ?t < card ?s"
   proof (unfold path_compression_invariant_def, intro conjI)
     have 3: "mapping ?p"
-      using 1 by (meson path_compression_invariant_def path_compression_precondition_def update_mapping bijective_regular)
+      by (simp add: i1 i3 i5 bijective_regular update_total update_univalent)
     have 4: "w \<noteq> y"
-      using 1 by (metis (no_types, hide_lams) path_compression_invariant_def path_compression_precondition_def root_successor_loop)
+      using 1 i1 i4 root_successor_loop by blast
     hence 5: "w \<sqinter> y = bot"
-      using 1 distinct_points path_compression_invariant_def path_compression_precondition_def by auto
+      by (simp add: i3 i5 distinct_points)
     hence "y * w\<^sup>T \<le> -1"
       using pseudo_complement schroeder_4_p by auto
     hence "y * w\<^sup>T \<le> p\<^sup>T\<^sup>\<star> \<sqinter> -1"
-      using 1 shunt_bijective path_compression_invariant_def by auto
+      using i5 i6 shunt_bijective by auto
     also have "... \<le> p\<^sup>T\<^sup>+"
       by (simp add: star_plus_without_loops)
     finally have 6: "y \<le> p\<^sup>T\<^sup>+ * w"
-      using 1 shunt_bijective path_compression_invariant_def by blast
+      using i5 shunt_bijective by auto
     have 7: "w * w\<^sup>T \<le> -p\<^sup>T\<^sup>+"
     proof (rule ccontr)
       assume "\<not> w * w\<^sup>T \<le> -p\<^sup>T\<^sup>+"
       hence "w * w\<^sup>T \<le> --p\<^sup>T\<^sup>+"
-        using 1 path_compression_invariant_def point_arc arc_in_partition by blast
+        using i5 point_arc arc_in_partition by blast
       hence "w * w\<^sup>T \<le> p\<^sup>T\<^sup>+ \<sqinter> 1"
-        using 1 path_compression_invariant_def path_compression_precondition_def mapping_regular regular_conv_closed regular_closed_star regular_mult_closed by simp
+        using i1 i5 mapping_regular regular_conv_closed regular_closed_star regular_mult_closed by simp
       also have "... = ((p\<^sup>T \<sqinter> 1) * p\<^sup>T\<^sup>\<star> \<sqinter> 1) \<squnion> ((p\<^sup>T \<sqinter> -1) * p\<^sup>T\<^sup>\<star> \<sqinter> 1)"
         by (metis comp_inf.mult_right_dist_sup maddux_3_11_pp mult_right_dist_sup regular_one_closed)
       also have "... = ((p\<^sup>T \<sqinter> 1) * p\<^sup>T\<^sup>\<star> \<sqinter> 1) \<squnion> ((p \<sqinter> -1)\<^sup>+ \<sqinter> 1)\<^sup>T"
         by (metis conv_complement conv_dist_inf conv_plus_commute equivalence_one_closed reachable_without_loops)
       also have "... \<le> ((p\<^sup>T \<sqinter> 1) * p\<^sup>T\<^sup>\<star> \<sqinter> 1) \<squnion> (-1 \<sqinter> 1)\<^sup>T"
-        using 1 by (metis (no_types, hide_lams) path_compression_invariant_def path_compression_precondition_def sup_right_isotone inf.sup_left_isotone conv_isotone)
+        by (metis (no_types, hide_lams) i1 sup_right_isotone inf.sup_left_isotone conv_isotone)
       also have "... = (p\<^sup>T \<sqinter> 1) * p\<^sup>T\<^sup>\<star> \<sqinter> 1"
         by simp
       also have "... \<le> (p\<^sup>T \<sqinter> 1) * top \<sqinter> 1"
         by (metis comp_inf.comp_isotone coreflexive_comp_top_inf equivalence_one_closed inf.cobounded1 inf.cobounded2)
       also have "... \<le> p\<^sup>T"
         by (simp add: coreflexive_comp_top_inf_one)
       finally have "w * w\<^sup>T \<le> p\<^sup>T"
         by simp
       hence "w \<le> p[[w]]"
-        using 1 path_compression_invariant_def shunt_bijective by blast
+        using i5 shunt_bijective by blast
       hence "w = p[[w]]"
-        using 1 2 path_compression_invariant_def epm_3 by fastforce
-      hence "w = p\<^sup>T\<^sup>+ * w"
-        using 2 by (metis comp_associative star.circ_top star_simulation_right_equal)
+        using 2 by (metis i5 epm_3 mult_semi_associative)
       thus False
-        using 1 4 6 epm_3 path_compression_invariant_def path_compression_precondition_def by fastforce
+        using 4 i11 by auto
     qed
     hence 8: "w \<sqinter> p\<^sup>T\<^sup>+ * w = bot"
       using p_antitone_iff pseudo_complement schroeder_4_p by blast
     show "y \<le> ?p\<^sup>T\<^sup>\<star> * (p[[w]])"
     proof -
       have "(w \<sqinter> y\<^sup>T)\<^sup>T * (-w \<sqinter> p)\<^sup>T\<^sup>\<star> * p\<^sup>T * w \<le> w\<^sup>T * (-w \<sqinter> p)\<^sup>T\<^sup>\<star> * p\<^sup>T * w"
         by (simp add: conv_isotone mult_left_isotone)
       also have "... \<le> w\<^sup>T * p\<^sup>T\<^sup>\<star> * p\<^sup>T * w"
         by (simp add: conv_isotone mult_left_isotone star_isotone mult_right_isotone)
       also have "... = w\<^sup>T * p\<^sup>T\<^sup>+ * w"
         by (simp add: star_plus mult_assoc)
       also have "... = bot"
-        using 1 8 by (metis (no_types, hide_lams) path_compression_invariant_def covector_inf_comp_3 mult_assoc conv_dist_comp conv_star_commute covector_bot_closed equivalence_top_closed inf.le_iff_sup mult_left_isotone)
+        using 8 by (smt i5 covector_inf_comp_3 mult_assoc conv_dist_comp conv_star_commute covector_bot_closed equivalence_top_closed inf.le_iff_sup mult_left_isotone)
       finally have "((w \<sqinter> y\<^sup>T)\<^sup>T \<squnion> (-w \<sqinter> p)\<^sup>T) * (-w \<sqinter> p)\<^sup>T\<^sup>\<star> * p\<^sup>T * w \<le> (-w \<sqinter> p)\<^sup>T * (-w \<sqinter> p)\<^sup>T\<^sup>\<star> * p\<^sup>T * w"
         by (simp add: bot_unique mult_right_dist_sup)
       also have "... \<le> (-w \<sqinter> p)\<^sup>T\<^sup>\<star> * p\<^sup>T * w"
         by (simp add: mult_left_isotone star.left_plus_below_circ)
       finally have "?p\<^sup>T * (-w \<sqinter> p)\<^sup>T\<^sup>\<star> * p\<^sup>T * w \<le> (-w \<sqinter> p)\<^sup>T\<^sup>\<star> * p\<^sup>T * w"
         by (simp add: conv_dist_sup)
       hence "?p\<^sup>T\<^sup>\<star> * p\<^sup>T * w \<le> (-w \<sqinter> p)\<^sup>T\<^sup>\<star> * p\<^sup>T * w"
         by (metis comp_associative star.circ_loop_fixpoint star_left_induct sup_commute sup_least sup_left_divisibility)
       hence "w \<sqinter> ?p\<^sup>T\<^sup>\<star> * p\<^sup>T * w \<le> w \<sqinter> (-w \<sqinter> p)\<^sup>T\<^sup>\<star> * p\<^sup>T * w"
         using inf.sup_right_isotone by blast
       also have "... \<le> w \<sqinter> p\<^sup>T\<^sup>\<star> * p\<^sup>T * w"
         using conv_isotone mult_left_isotone star_isotone inf.sup_right_isotone by simp
       also have "... = bot"
         using 8 by (simp add: star_plus)
       finally have 9: "w\<^sup>T * ?p\<^sup>T\<^sup>\<star> * p\<^sup>T * w = bot"
-        using 1 by (metis (no_types, hide_lams) path_compression_invariant_def covector_inf_comp_3 mult_assoc conv_dist_comp covector_bot_closed equivalence_top_closed inf.le_iff_sup mult_left_isotone bot_least inf.absorb1)
+        by (smt i5 covector_inf_comp_3 mult_assoc conv_dist_comp covector_bot_closed equivalence_top_closed inf.le_iff_sup mult_left_isotone bot_least inf.absorb1)
       have "p\<^sup>T * ?p\<^sup>T\<^sup>\<star> * p\<^sup>T * w = ((w \<sqinter> p)\<^sup>T \<squnion> (-w \<sqinter> p)\<^sup>T) * ?p\<^sup>T\<^sup>\<star> * p\<^sup>T * w"
-        using 1 by (metis (no_types, lifting) bijective_regular conv_dist_sup inf_commute maddux_3_11_pp path_compression_invariant_def)
+        by (metis i5 bijective_regular conv_dist_sup inf.sup_monoid.add_commute maddux_3_11_pp)
       also have "... = (w \<sqinter> p)\<^sup>T * ?p\<^sup>T\<^sup>\<star> * p\<^sup>T * w \<squnion> (-w \<sqinter> p)\<^sup>T * ?p\<^sup>T\<^sup>\<star> * p\<^sup>T * w"
         by (simp add: mult_right_dist_sup)
       also have "... \<le> w\<^sup>T * ?p\<^sup>T\<^sup>\<star> * p\<^sup>T * w \<squnion> (-w \<sqinter> p)\<^sup>T * ?p\<^sup>T\<^sup>\<star> * p\<^sup>T * w"
         using semiring.add_right_mono comp_isotone conv_isotone by auto
       also have "... = (-w \<sqinter> p)\<^sup>T * ?p\<^sup>T\<^sup>\<star> * p\<^sup>T * w"
         using 9 by simp
       also have "... \<le> ?p\<^sup>T\<^sup>+ * p\<^sup>T * w"
         by (simp add: conv_isotone mult_left_isotone)
       also have "... \<le> ?p\<^sup>T\<^sup>\<star> * p\<^sup>T * w"
         by (simp add: comp_isotone star.left_plus_below_circ)
       finally have "p\<^sup>T\<^sup>\<star> * p\<^sup>T * w \<le> ?p\<^sup>T\<^sup>\<star> * p\<^sup>T * w"
         by (metis comp_associative star.circ_loop_fixpoint star_left_induct sup_commute sup_least sup_left_divisibility)
       thus "y \<le> ?p\<^sup>T\<^sup>\<star> * (p[[w]])"
         using 6 by (simp add: star_simulation_right_equal mult_assoc)
     qed
     have 10: "acyclic (?p \<sqinter> -1)"
-      using 1 update_acyclic_1 path_compression_invariant_def path_compression_precondition_def by auto
+      using i1 i10 i3 i5 inf_le1 update_acyclic_3 by blast
     have "?p[[p\<^sup>T\<^sup>+ * w]] \<le> p\<^sup>T\<^sup>+ * w"
     proof -
       have "(w\<^sup>T \<sqinter> y) * p\<^sup>T\<^sup>+ * w = y \<sqinter> w\<^sup>T * p\<^sup>T\<^sup>+ * w"
-        using 1 by (metis (no_types, hide_lams) path_compression_invariant_def path_compression_precondition_def inf_commute vector_inf_comp)
+        by (metis i3 inf_vector_comp vector_inf_comp)
       hence "?p[[p\<^sup>T\<^sup>+ * w]] = (y \<sqinter> w\<^sup>T * p\<^sup>T\<^sup>+ * w) \<squnion> (-w\<^sup>T \<sqinter> p\<^sup>T) * p\<^sup>T\<^sup>+ * w"
         by (simp add: comp_associative conv_complement conv_dist_inf conv_dist_sup mult_right_dist_sup)
       also have "... \<le> y \<squnion> (-w\<^sup>T \<sqinter> p\<^sup>T) * p\<^sup>T\<^sup>+ * w"
         using sup_left_isotone by auto
       also have "... \<le> y \<squnion> p\<^sup>T * p\<^sup>T\<^sup>+ * w"
         using mult_left_isotone sup_right_isotone by auto
       also have "... \<le> y \<squnion> p\<^sup>T\<^sup>+ * w"
         using semiring.add_left_mono mult_left_isotone mult_right_isotone star.left_plus_below_circ by auto
       also have "... = p\<^sup>T\<^sup>+ * w"
         using 6 by (simp add: sup_absorb2)
       finally show ?thesis
         by simp
     qed
     hence 11: "?p\<^sup>T\<^sup>\<star> * (p[[w]]) \<le> p\<^sup>T\<^sup>+ * w"
       using star_left_induct by (simp add: mult_left_isotone star.circ_mult_increasing)
     hence 12: "?p\<^sup>T\<^sup>+ * (p[[w]]) \<le> p\<^sup>T\<^sup>+ * w"
       using dual_order.trans mult_left_isotone star.left_plus_below_circ by blast
     have 13: "?p[[x]] = y \<and> y \<noteq> x \<and> ?p\<^sup>T\<^sup>+ * (p[[w]]) \<le> -x"
     proof (cases "w = x")
       case True
       hence "?p[[x]] = (w\<^sup>T \<sqinter> y) * w \<squnion> (-w\<^sup>T \<sqinter> p\<^sup>T) * w"
         by (simp add: conv_complement conv_dist_inf conv_dist_sup mult_right_dist_sup)
       also have "... = (w\<^sup>T \<sqinter> y) * w \<squnion> p\<^sup>T * (-w \<sqinter> w)"
-        using 1 by (metis (no_types, lifting) conv_complement inf.sup_monoid.add_commute path_compression_invariant_def covector_inf_comp_3 vector_complement_closed)
+        by (metis i5 conv_complement covector_inf_comp_3 inf.sup_monoid.add_commute vector_complement_closed)
       also have "... = (w\<^sup>T \<sqinter> y) * w"
         by simp
       also have "... = y * w"
-        using 1 inf.sup_monoid.add_commute path_compression_invariant_def covector_inf_comp_3 by simp
+        by (simp add: i5 covector_inf_comp_3 inf.sup_monoid.add_commute)
       also have "... = y"
-        using 1 by (metis comp_associative path_compression_precondition_def path_compression_invariant_def)
+        by (metis i3 i5 comp_associative)
       finally show ?thesis
         using 4 8 12 True pseudo_complement inf.sup_monoid.add_commute order.trans by blast
     next
       case False
       have "?p[[x]] = (w\<^sup>T \<sqinter> y) * x \<squnion> (-w\<^sup>T \<sqinter> p\<^sup>T) * x"
         by (simp add: conv_complement conv_dist_inf conv_dist_sup mult_right_dist_sup)
       also have "... = y * (w \<sqinter> x) \<squnion> p\<^sup>T * (-w \<sqinter> x)"
-        using 1 by (metis (no_types, lifting) conv_complement inf.sup_monoid.add_commute path_compression_invariant_def covector_inf_comp_3 vector_complement_closed)
+        by (metis i5 conv_complement covector_inf_comp_3 inf_commute vector_complement_closed)
       also have "... = p\<^sup>T * (-w \<sqinter> x)"
-        using 1 False path_compression_invariant_def path_compression_precondition_def distinct_points by auto
+        using i2 i5 False distinct_points by auto
       also have "... = y"
-        using 1 False path_compression_invariant_def path_compression_precondition_def distinct_points inf.absorb2 pseudo_complement by auto
+        using i2 i5 i7 False distinct_points inf.absorb2 pseudo_complement by auto
       finally show ?thesis
-        using 1 12 False path_compression_invariant_def by auto
+        using 12 False i7 dual_order.trans by blast
     qed
     thus "p[[w]] \<noteq> x \<longrightarrow> ?p[[x]] = y \<and> y \<noteq> x \<and> ?p\<^sup>T\<^sup>+ * (p[[w]]) \<le> -x"
       by simp
     have 14: "?p\<^sup>T\<^sup>\<star> * x = x \<squnion> y"
     proof (rule antisym)
       have "?p\<^sup>T * (x \<squnion> y) = y \<squnion> ?p\<^sup>T * y"
         using 13 by (simp add: mult_left_dist_sup)
       also have "... = y \<squnion> (w\<^sup>T \<sqinter> y) * y \<squnion> (-w\<^sup>T \<sqinter> p\<^sup>T) * y"
         by (simp add: conv_complement conv_dist_inf conv_dist_sup mult_right_dist_sup sup_assoc)
       also have "... \<le> y \<squnion> (w\<^sup>T \<sqinter> y) * y \<squnion> p\<^sup>T * y"
         using mult_left_isotone sup_right_isotone by auto
       also have "... = y \<squnion> (w\<^sup>T \<sqinter> y) * y"
-        using 1 by (smt sup.cobounded1 sup_absorb1 path_compression_invariant_def path_compression_precondition_def root_successor_loop)
+        using i1 i10 root_successor_loop sup_commute by auto
       also have "... \<le> y \<squnion> y * y"
         using mult_left_isotone sup_right_isotone by auto
       also have "... = y"
-        using 1 by (metis mult_semi_associative sup_absorb1 path_compression_invariant_def path_compression_precondition_def)
+        by (metis i3 comp_associative sup.idem)
       also have "... \<le> x \<squnion> y"
         by simp
       finally show "?p\<^sup>T\<^sup>\<star> * x \<le> x \<squnion> y"
         by (simp add: star_left_induct)
     next
       show "x \<squnion> y \<le> ?p\<^sup>T\<^sup>\<star> * x"
         using 13 by (metis mult_left_isotone star.circ_increasing star.circ_loop_fixpoint sup.boundedI sup_ge2)
     qed
     have 15: "y = root ?p x"
     proof -
       have "(p \<sqinter> 1) * y = (p \<sqinter> 1) * (p \<sqinter> 1) * p\<^sup>T\<^sup>\<star> * x"
-        using 1 path_compression_invariant_def path_compression_precondition_def root_var mult_assoc by auto
+        by (simp add: i4 comp_associative root_var)
       also have "... = (p \<sqinter> 1) * p\<^sup>T\<^sup>\<star> * x"
         using coreflexive_idempotent by auto
       finally have 16: "(p \<sqinter> 1) * y = y"
-        using 1 path_compression_invariant_def path_compression_precondition_def root_var by auto
+        by (simp add: i4 root_var)
       have 17: "(p \<sqinter> 1) * x \<le> y"
-        using 1 by (metis (no_types, lifting) comp_right_one mult_left_isotone mult_right_isotone star.circ_reflexive path_compression_invariant_def path_compression_precondition_def root_var)
+        by (metis (no_types, lifting) i4 comp_right_one mult_left_isotone mult_right_isotone star.circ_reflexive root_var)
       have "root ?p x = (?p \<sqinter> 1) * (x \<squnion> y)"
         using 14 by (metis mult_assoc root_var)
       also have "... = (w \<sqinter> y\<^sup>T \<sqinter> 1) * (x \<squnion> y) \<squnion> (-w \<sqinter> p \<sqinter> 1) * (x \<squnion> y)"
         by (simp add: inf_sup_distrib2 semiring.distrib_right)
       also have "... = (w \<sqinter> 1 \<sqinter> y\<^sup>T) * (x \<squnion> y) \<squnion> (-w \<sqinter> p \<sqinter> 1) * (x \<squnion> y)"
         by (simp add: inf.left_commute inf.sup_monoid.add_commute)
       also have "... = (w \<sqinter> 1) * (y \<sqinter> (x \<squnion> y)) \<squnion> (-w \<sqinter> p \<sqinter> 1) * (x \<squnion> y)"
-        using 1 by (metis (no_types, lifting) path_compression_invariant_def path_compression_precondition_def covector_inf_comp_3)
+        by (simp add: i3 covector_inf_comp_3)
       also have "... = (w \<sqinter> 1) * y \<squnion> (-w \<sqinter> p \<sqinter> 1) * (x \<squnion> y)"
         by (simp add: inf.absorb1)
       also have "... = (w \<sqinter> 1 * y) \<squnion> (-w \<sqinter> (p \<sqinter> 1) * (x \<squnion> y))"
-        using 1 by (metis (no_types, lifting) inf_assoc vector_complement_closed path_compression_invariant_def vector_inf_comp)
+        by (simp add: i5 inf_assoc vector_complement_closed vector_inf_comp)
       also have "... = (w \<sqinter> y) \<squnion> (-w \<sqinter> ((p \<sqinter> 1) * x \<squnion> y))"
         using 16 by (simp add: mult_left_dist_sup)
       also have "... = (w \<sqinter> y) \<squnion> (-w \<sqinter> y)"
         using 17 by (simp add: sup.absorb2)
       also have "... = y"
-        using 1 by (metis id_apply bijective_regular comp_inf.mult_right_dist_sup comp_inf.vector_conv_covector inf_top.right_neutral regular_complement_top path_compression_invariant_def)
+        using 5 inf.sup_monoid.add_commute le_iff_inf pseudo_complement sup_monoid.add_0_left by fastforce
       finally show ?thesis
         by simp
     qed
     show "path_compression_precondition ?p x y"
-      using 1 3 10 15 path_compression_invariant_def path_compression_precondition_def by auto
+      using 3 10 15 i2 i3 path_compression_precondition_def by blast
     show "vector (p[[w]])"
       using 2 by simp
     show "injective (p[[w]])"
       using 2 by simp
     show "surjective (p[[w]])"
       using 2 by simp
     have "w \<sqinter> p \<sqinter> 1 \<le> w \<sqinter> w\<^sup>T \<sqinter> p"
       by (metis inf.boundedE inf.boundedI inf.cobounded1 inf.cobounded2 one_inf_conv)
     also have "... = w * w\<^sup>T \<sqinter> p"
-      using 1 vector_covector path_compression_invariant_def by auto
+      by (simp add: i5 vector_covector)
     also have "... \<le> -p\<^sup>T\<^sup>+ \<sqinter> p"
       using 7 by (simp add: inf.coboundedI2 inf.sup_monoid.add_commute)
     finally have "w \<sqinter> p \<sqinter> 1 = bot"
       by (metis (no_types, hide_lams) conv_dist_inf coreflexive_symmetric inf.absorb1 inf.boundedE inf.cobounded2 pseudo_complement star.circ_mult_increasing)
     also have "w \<sqinter> y\<^sup>T \<sqinter> 1 = bot"
       using 5 antisymmetric_bot_closed asymmetric_bot_closed comp_inf.schroeder_2 inf.absorb1 one_inf_conv by fastforce
     finally have "w \<sqinter> p \<sqinter> 1 = w \<sqinter> y\<^sup>T \<sqinter> 1"
       by simp
-    thus "?p \<sqinter> 1 = p0 \<sqinter> 1"
-      using 1 by (metis bijective_regular comp_inf.semiring.distrib_left inf.sup_monoid.add_commute maddux_3_11_pp path_compression_invariant_def)
-    show "fc ?p = fc p0"
+    thus 18: "?p \<sqinter> 1 = p0 \<sqinter> 1"
+      by (metis i5 i8 bijective_regular inf.sup_monoid.add_commute inf_sup_distrib2 maddux_3_11_pp)
+    show 19: "fc ?p = fc p0"
     proof -
       have "p[[w]] = p\<^sup>T * (w \<sqinter> p\<^sup>\<star> * y)"
-        using 1 by (metis (no_types, lifting) bijective_reverse conv_star_commute inf.absorb1 path_compression_invariant_def path_compression_precondition_def)
+        by (metis i3 i5 i6 bijective_reverse conv_star_commute inf.absorb1)
       also have "... = p\<^sup>T * (w \<sqinter> p\<^sup>\<star>) * y"
-        using 1 vector_inf_comp path_compression_invariant_def mult_assoc by auto
+        by (simp add: i5 vector_inf_comp mult_assoc)
       also have "... = p\<^sup>T * ((w \<sqinter> 1) \<squnion> (w \<sqinter> p) * (-w \<sqinter> p)\<^sup>\<star>) * y"
-        using 1 omit_redundant_points path_compression_invariant_def by auto
+        by (simp add: i5 omit_redundant_points)
       also have "... = p\<^sup>T * (w \<sqinter> 1) * y \<squnion> p\<^sup>T * (w \<sqinter> p) * (-w \<sqinter> p)\<^sup>\<star> * y"
         by (simp add: comp_associative mult_left_dist_sup mult_right_dist_sup)
       also have "... \<le> p\<^sup>T * y \<squnion> p\<^sup>T * (w \<sqinter> p) * (-w \<sqinter> p)\<^sup>\<star> * y"
         by (metis semiring.add_right_mono comp_isotone eq_iff inf.cobounded1 inf.sup_monoid.add_commute mult_1_right)
       also have "... = y \<squnion> p\<^sup>T * (w \<sqinter> p) * (-w \<sqinter> p)\<^sup>\<star> * y"
-        using 1 path_compression_invariant_def path_compression_precondition_def root_successor_loop by fastforce
+        using i1 i4 root_successor_loop by auto
       also have "... \<le> y \<squnion> p\<^sup>T * p * (-w \<sqinter> p)\<^sup>\<star> * y"
         using comp_isotone sup_right_isotone by auto
       also have "... \<le> y \<squnion> (-w \<sqinter> p)\<^sup>\<star> * y"
-        using 1 by (metis (no_types, lifting) mult_left_isotone star.circ_circ_mult star_involutive star_one sup_right_isotone path_compression_invariant_def path_compression_precondition_def)
+        by (metis i1 comp_associative eq_refl shunt_mapping sup_right_isotone)
       also have "... = (-w \<sqinter> p)\<^sup>\<star> * y"
         by (metis star.circ_loop_fixpoint sup.left_idem sup_commute)
-      finally have 18: "p[[w]] \<le> (-w \<sqinter> p)\<^sup>\<star> * y"
+      finally have 20: "p[[w]] \<le> (-w \<sqinter> p)\<^sup>\<star> * y"
         by simp
       have "p\<^sup>T * (-w \<sqinter> p)\<^sup>\<star> * y = p\<^sup>T * y \<squnion> p\<^sup>T * (-w \<sqinter> p) * (-w \<sqinter> p)\<^sup>\<star> * y"
         by (metis comp_associative mult_left_dist_sup star.circ_loop_fixpoint sup_commute)
       also have "... = y \<squnion> p\<^sup>T * (-w \<sqinter> p) * (-w \<sqinter> p)\<^sup>\<star> * y"
-        using 1 path_compression_invariant_def path_compression_precondition_def root_successor_loop by fastforce
+        using i1 i4 root_successor_loop by auto
       also have "... \<le> y \<squnion> p\<^sup>T * p * (-w \<sqinter> p)\<^sup>\<star> * y"
         using comp_isotone sup_right_isotone by auto
       also have "... \<le> y \<squnion> (-w \<sqinter> p)\<^sup>\<star> * y"
-        using 1 by (metis (no_types, lifting) mult_left_isotone star.circ_circ_mult star_involutive star_one sup_right_isotone path_compression_invariant_def path_compression_precondition_def)
+        by (metis i1 comp_associative eq_refl shunt_mapping sup_right_isotone)
       also have "... = (-w \<sqinter> p)\<^sup>\<star> * y"
         by (metis star.circ_loop_fixpoint sup.left_idem sup_commute)
-      finally have 19: "p\<^sup>T\<^sup>\<star> * p\<^sup>T * w \<le> (-w \<sqinter> p)\<^sup>\<star> * y"
-        using 18 by (simp add: comp_associative star_left_induct)
+      finally have 21: "p\<^sup>T\<^sup>\<star> * p\<^sup>T * w \<le> (-w \<sqinter> p)\<^sup>\<star> * y"
+        using 20 by (simp add: comp_associative star_left_induct)
       have "w\<^sup>T \<sqinter> p\<^sup>T = p\<^sup>T * (w\<^sup>T \<sqinter> 1)"
-        using 1 by (metis conv_dist_comp conv_dist_inf equivalence_one_closed vector_inf_one_comp path_compression_invariant_def)
+        by (metis i5 comp_right_one covector_inf_comp_3 inf.sup_monoid.add_commute one_inf_conv)
       also have "... \<le> p[[w]]"
         by (metis comp_right_subdist_inf inf.boundedE inf.sup_monoid.add_commute one_inf_conv)
       also have "... \<le> p\<^sup>T\<^sup>\<star> * p\<^sup>T * w"
         by (simp add: mult_left_isotone star.circ_mult_increasing_2)
       also have "... \<le> (-w \<sqinter> p)\<^sup>\<star> * y"
-        using 19 by simp
+        using 21 by simp
       finally have "w \<sqinter> p \<le> y\<^sup>T * (-w \<sqinter> p)\<^sup>T\<^sup>\<star>"
         by (metis conv_dist_comp conv_dist_inf conv_involutive conv_isotone conv_star_commute)
       hence "w \<sqinter> p \<le> (w \<sqinter> y\<^sup>T) * (-w \<sqinter> p)\<^sup>T\<^sup>\<star>"
-        using 1 by (metis inf.absorb1 inf.left_commute inf.left_idem inf.orderI vector_inf_comp path_compression_invariant_def)
+        by (simp add: i5 vector_inf_comp)
       also have "... \<le> (w \<sqinter> y\<^sup>T) * ?p\<^sup>T\<^sup>\<star>"
         by (simp add: conv_isotone mult_right_isotone star_isotone)
       also have "... \<le> ?p * ?p\<^sup>T\<^sup>\<star>"
         by (simp add: mult_left_isotone)
       also have "... \<le> fc ?p"
         by (simp add: mult_left_isotone star.circ_increasing)
-      finally have 20: "w \<sqinter> p \<le> fc ?p"
+      finally have 22: "w \<sqinter> p \<le> fc ?p"
         by simp
       have "-w \<sqinter> p \<le> ?p"
         by simp
       also have "... \<le> fc ?p"
         by (simp add: fc_increasing)
       finally have "(w \<squnion> -w) \<sqinter> p \<le> fc ?p"
-        using 20 by (simp add: comp_inf.semiring.distrib_left inf.sup_monoid.add_commute)
+        using 22 by (simp add: comp_inf.semiring.distrib_left inf.sup_monoid.add_commute)
       hence "p \<le> fc ?p"
-        using 1 by (metis (no_types, hide_lams) bijective_regular comp_inf.semiring.distrib_left inf.sup_monoid.add_commute maddux_3_11_pp path_compression_invariant_def)
-      hence 21: "fc p \<le> fc ?p"
+        by (metis i5 bijective_regular inf.sup_monoid.add_commute inf_sup_distrib1 maddux_3_11_pp)
+      hence 23: "fc p \<le> fc ?p"
         using 3 fc_idempotent fc_isotone by fastforce
       have "?p \<le> (w \<sqinter> y\<^sup>T) \<squnion> p"
         using sup_right_isotone by auto
       also have "... = w * y\<^sup>T \<squnion> p"
-        using 1 path_compression_invariant_def path_compression_precondition_def vector_covector by auto
+        by (simp add: i3 i5 vector_covector)
       also have "... \<le> p\<^sup>\<star> \<squnion> p"
-        using 1 by (metis (no_types, lifting) conv_dist_comp conv_involutive conv_isotone conv_star_commute le_supI shunt_bijective star.circ_increasing sup_absorb1 path_compression_invariant_def)
+        by (smt i5 i6 conv_dist_comp conv_involutive conv_isotone conv_star_commute le_supI shunt_bijective star.circ_increasing sup_absorb1)
       also have "... \<le> fc p"
         using fc_increasing star.circ_back_loop_prefixpoint by auto
       finally have "fc ?p \<le> fc p"
-        using 1 by (metis (no_types, lifting) path_compression_invariant_def path_compression_precondition_def fc_idempotent fc_isotone)
+        using i1 fc_idempotent fc_isotone by fastforce
       thus ?thesis
-        using 1 21 path_compression_invariant_def by simp
+        using 23 i9 by auto
+    qed
+    show "?p[[p[[w]]]] = p0[[p[[w]]]]"
+    proof -
+      have "?p[[p[[w]]]] = p[[p[[w]]]]"
+        using 2 4 i5 i11 by (simp add: put_get_different)
+      also have "... = p[[p0[[w]]]]"
+        by (simp add: i12)
+      also have "... = (p0[p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * w)\<longmapsto>y])[[p0[[w]]]]"
+        using i13 by auto
+      also have "... = p0[[p0[[w]]]]"
+      proof -
+        have "p0[[w]] \<le> -(p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * w))"
+          by (meson inf.coboundedI2 mult_left_isotone p_antitone p_antitone_iff star.circ_increasing)
+        thus ?thesis
+          by (meson i2 i5 put_get_different_vector vector_complement_closed vector_inf_closed vector_mult_closed)
+      qed
+      also have "... = p0[[p[[w]]]]"
+        by (simp add: i12)
+      finally show ?thesis
+        .
+    qed
+    have 24: "root ?p (p[[w]]) = root p0 (p[[w]])"
+      using 3 18 19 i14 same_root by blast
+    also have "... = root p0 (p0[[w]])"
+      by (simp add: i12)
+    also have 25: "... = root p0 w"
+      by (metis i5 i14 conv_involutive forest_components_increasing mult_left_isotone shunt_bijective injective_mult_closed read_surjective same_component_same_root)
+    finally show 26: "root ?p (p[[w]]) = y"
+      by (metis i1 i10 i14 i8 i9 same_root)
+    show "p[[w]] \<noteq> y \<longrightarrow> ?p[[p[[w]]]] \<noteq> p[[w]] \<and> ?p\<^sup>T\<^sup>+ * (p[[w]]) \<le> -(p[[w]])"
+    proof
+      assume 27: "p[[w]] \<noteq> y"
+      show "?p[[p[[w]]]] \<noteq> p[[w]] \<and> ?p\<^sup>T\<^sup>+ * (p[[w]]) \<le> -(p[[w]])"
+      proof
+        show "?p[[p[[w]]]] \<noteq> p[[w]]"
+          using 2 26 27 loop_root by auto
+        show "?p\<^sup>T\<^sup>+ * (p[[w]]) \<le> -(p[[w]])"
+          using 2 3 10 26 27 by (simp add: path_compression_1a)
+      qed
+    qed
+    show "univalent p0" "total p0" "acyclic (p0 \<sqinter> -1)"
+      by (simp_all add: i14)
+    show "y = root p0 x"
+      by (simp add: i15)
+    show "p[[w]] \<le> p0\<^sup>T\<^sup>\<star> * x"
+      by (metis i12 i16 mult_isotone star.circ_increasing star.circ_transitive_equal mult_assoc)
+    let ?q = "p0[p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * (p[[w]]))\<longmapsto>y]"
+    show "?q = ?p"
+    proof -
+      have 28: "w \<squnion> p0\<^sup>T\<^sup>+ * w = p0\<^sup>T\<^sup>\<star> * w"
+        using comp_associative star.circ_loop_fixpoint sup_commute by auto
+      hence 29: "p0\<^sup>T\<^sup>+ * w = p0\<^sup>T\<^sup>\<star> * w \<sqinter> -w"
+        using 4 24 25 26 by (metis i12 i14 i5 inf.orderE maddux_3_13 path_compression_1a)
+      hence "p0\<^sup>T\<^sup>\<star> * (p[[w]]) \<le> -w"
+        by (metis i12 inf_le2 star_plus mult.assoc)
+      hence "w \<le> -(p0\<^sup>T\<^sup>\<star> * (p[[w]]))"
+        by (simp add: p_antitone_iff)
+      hence "w \<le> p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * (p[[w]]))"
+        by (simp add: i16)
+      hence 30: "?q \<sqinter> w = ?p \<sqinter> w"
+        by (metis update_inf update_inf_same)
+      have 31: "?q \<sqinter> p0\<^sup>T\<^sup>+ * w = ?p \<sqinter> p0\<^sup>T\<^sup>+ * w"
+      proof -
+        have "?q \<sqinter> p0\<^sup>T\<^sup>+ * w = p0 \<sqinter> p0\<^sup>T\<^sup>+ * w"
+          by (metis i12 comp_associative inf.cobounded2 p_antitone_iff star.circ_plus_same update_inf_different)
+        also have "... = p \<sqinter> p0\<^sup>T\<^sup>+ * w"
+          using 29 by (metis i13 inf.cobounded2 inf.sup_monoid.add_assoc p_antitone_iff update_inf_different)
+        also have "... = ?p \<sqinter> p0\<^sup>T\<^sup>+ * w"
+          using 29 by (simp add: update_inf_different)
+        finally show ?thesis
+          .
+      qed
+      have 32: "?q \<sqinter> p0\<^sup>T\<^sup>\<star> * w = ?p \<sqinter> p0\<^sup>T\<^sup>\<star> * w"
+        using 28 30 31 by (metis inf_sup_distrib1)
+      have 33: "?q \<sqinter> (p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * w)) = ?p \<sqinter> (p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * w))"
+      proof -
+        have "p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * w) \<le> p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * (p[[w]]))"
+          using 29 by (metis i12 inf.sup_right_isotone mult.semigroup_axioms p_antitone_inf star_plus semigroup.assoc)
+        hence "?q \<sqinter> (p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * w)) = y\<^sup>T \<sqinter> p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * w)"
+          by (metis inf_assoc update_inf)
+        also have "... = p \<sqinter> (p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * w))"
+          by (metis i13 inf_assoc update_inf_same)
+        also have "... = ?p \<sqinter> (p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * w))"
+          by (simp add: inf.coboundedI2 p_antitone path_compression_1b inf_assoc update_inf_different)
+        finally show ?thesis
+          .
+      qed
+      have "p0\<^sup>T\<^sup>\<star> * w \<squnion> (p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * w)) = p0\<^sup>T\<^sup>\<star> * x"
+      proof -
+        have 34: "regular (p0\<^sup>T\<^sup>\<star> * w)"
+          using i14 i5 bijective_regular mapping_regular regular_closed_star regular_conv_closed regular_mult_closed by auto
+        have "p0\<^sup>T\<^sup>\<star> * w \<le> p0\<^sup>T\<^sup>\<star> * x"
+          by (metis i16 comp_associative mult_right_isotone star.circ_transitive_equal)
+        hence "p0\<^sup>T\<^sup>\<star> * w \<squnion> (p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * w)) = p0\<^sup>T\<^sup>\<star> * x \<sqinter> (p0\<^sup>T\<^sup>\<star> * w \<squnion> -(p0\<^sup>T\<^sup>\<star> * w))"
+          by (simp add: comp_inf.semiring.distrib_left inf.absorb2)
+        also have "... = p0\<^sup>T\<^sup>\<star> * x"
+          using 34 by (metis inf_sup_distrib1 maddux_3_11_pp)
+        finally show ?thesis
+          .
+      qed
+      hence 35: "?q \<sqinter> p0\<^sup>T\<^sup>\<star> * x = ?p \<sqinter> p0\<^sup>T\<^sup>\<star> * x"
+        using 32 33 by (metis inf_sup_distrib1)
+      have 36: "regular (p0\<^sup>T\<^sup>\<star> * x)"
+        using i14 i2 bijective_regular mapping_regular regular_closed_star regular_conv_closed regular_mult_closed by auto
+      have "-(p0\<^sup>T\<^sup>\<star> * x) \<le> -w"
+        by (simp add: i16 p_antitone)
+      hence "?q \<sqinter> -(p0\<^sup>T\<^sup>\<star> * x) = ?p \<sqinter> -(p0\<^sup>T\<^sup>\<star> * x)"
+        by (metis i13 p_antitone_inf update_inf_different)
+      thus ?thesis
+        using 35 36 by (metis maddux_3_11_pp)
     qed
     show "card ?t < card ?s"
     proof -
       have "?p\<^sup>T * p\<^sup>T\<^sup>\<star> * w = (w\<^sup>T \<sqinter> y) * p\<^sup>T\<^sup>\<star> * w \<squnion> (-w\<^sup>T \<sqinter> p\<^sup>T) * p\<^sup>T\<^sup>\<star> * w"
         by (simp add: conv_complement conv_dist_inf conv_dist_sup mult_right_dist_sup)
       also have "... \<le> (w\<^sup>T \<sqinter> y) * p\<^sup>T\<^sup>\<star> * w \<squnion> p\<^sup>T * p\<^sup>T\<^sup>\<star> * w"
         using mult_left_isotone sup_right_isotone by auto
       also have "... \<le> (w\<^sup>T \<sqinter> y) * p\<^sup>T\<^sup>\<star> * w \<squnion> p\<^sup>T\<^sup>\<star> * w"
         using mult_left_isotone star.left_plus_below_circ sup_right_isotone by blast
       also have "... \<le> y * p\<^sup>T\<^sup>\<star> * w \<squnion> p\<^sup>T\<^sup>\<star> * w"
         using semiring.add_right_mono mult_left_isotone by auto
       also have "... \<le> y * top \<squnion> p\<^sup>T\<^sup>\<star> * w"
         by (simp add: comp_associative le_supI1 mult_right_isotone)
       also have "... = p\<^sup>T\<^sup>\<star> * w"
-        using 1 path_compression_invariant_def path_compression_precondition_def sup_absorb2 by auto
+        by (simp add: i3 i6 sup_absorb2)
       finally have "?p\<^sup>T\<^sup>\<star> * p\<^sup>T * w \<le> p\<^sup>T\<^sup>\<star> * w"
         using 11 by (metis dual_order.trans star.circ_loop_fixpoint sup_commute sup_ge2 mult_assoc)
-      hence 22: "?t \<subseteq> ?s"
+      hence 37: "?t \<subseteq> ?s"
         using order_lesseq_imp mult_assoc by auto
-      have 23: "w \<in> ?s"
-        using 1 bijective_regular path_compression_invariant_def eq_iff star.circ_loop_fixpoint by auto
-      have 24: "\<not> w \<in> ?t"
+      have 38: "w \<in> ?s"
+        by (simp add: i5 bijective_regular path_compression_1b)
+      have 39: "\<not> w \<in> ?t"
       proof
         assume "w \<in> ?t"
-        hence 25: "w \<le> (?p\<^sup>T \<sqinter> -1)\<^sup>\<star> * (p[[w]])"
+        hence 40: "w \<le> (?p\<^sup>T \<sqinter> -1)\<^sup>\<star> * (p[[w]])"
           using reachable_without_loops by auto
         hence "p[[w]] \<le> (?p \<sqinter> -1)\<^sup>\<star> * w"
-          using 1 2 by (metis (no_types, hide_lams) bijective_reverse conv_star_commute reachable_without_loops path_compression_invariant_def)
+          using 2 by (smt i5 bijective_reverse conv_star_commute reachable_without_loops)
         also have "... \<le> p\<^sup>\<star> * w"
         proof -
           have "p\<^sup>T\<^sup>\<star> * y = y"
-            using 1 path_compression_invariant_def path_compression_precondition_def root_transitive_successor_loop by fastforce
+            using i1 i4 root_transitive_successor_loop by auto
           hence "y\<^sup>T * p\<^sup>\<star> * w = y\<^sup>T * w"
             by (metis conv_dist_comp conv_involutive conv_star_commute)
           also have "... = bot"
-            using 1 5 by (metis (no_types, hide_lams) conv_dist_comp conv_dist_inf equivalence_top_closed inf_top.right_neutral schroeder_2 symmetric_bot_closed path_compression_invariant_def)
-          finally have 26: "y\<^sup>T * p\<^sup>\<star> * w = bot"
+            using 5 by (metis i5 inf.idem inf.sup_monoid.add_commute mult_left_zero schroeder_1 vector_inf_comp)
+          finally have 41: "y\<^sup>T * p\<^sup>\<star> * w = bot"
             by simp
           have "(?p \<sqinter> -1) * p\<^sup>\<star> * w = (w \<sqinter> y\<^sup>T \<sqinter> -1) * p\<^sup>\<star> * w \<squnion> (-w \<sqinter> p \<sqinter> -1) * p\<^sup>\<star> * w"
             by (simp add: comp_inf.mult_right_dist_sup mult_right_dist_sup)
           also have "... \<le> (w \<sqinter> y\<^sup>T \<sqinter> -1) * p\<^sup>\<star> * w \<squnion> p * p\<^sup>\<star> * w"
             by (meson inf_le1 inf_le2 mult_left_isotone order_trans sup_right_isotone)
           also have "... \<le> (w \<sqinter> y\<^sup>T \<sqinter> -1) * p\<^sup>\<star> * w \<squnion> p\<^sup>\<star> * w"
             using mult_left_isotone star.left_plus_below_circ sup_right_isotone by blast
           also have "... \<le> y\<^sup>T * p\<^sup>\<star> * w \<squnion> p\<^sup>\<star> * w"
             by (meson inf_le1 inf_le2 mult_left_isotone order_trans sup_left_isotone)
           also have "... = p\<^sup>\<star> * w"
-            using 26 by simp
+            using 41 by simp
           finally show ?thesis
             by (metis comp_associative le_supI star.circ_loop_fixpoint sup_ge2 star_left_induct)
         qed
         finally have "w \<le> p\<^sup>T\<^sup>\<star> * p\<^sup>T * w"
-          using 11 25 reachable_without_loops star_plus by auto
+          using 11 40 reachable_without_loops star_plus by auto
         thus False
-          using 1 7 by (metis inf.le_iff_sup le_bot pseudo_complement schroeder_4_p semiring.mult_zero_right star.circ_plus_same path_compression_invariant_def)
+          using 4 i1 i10 i5 loop_root_2 star.circ_plus_same by auto
       qed
       show "card ?t < card ?s"
         apply (rule psubset_card_mono)
         subgoal using finite_regular by simp
-        subgoal using 22 23 24 by auto
+        subgoal using 37 38 39 by auto
         done
     qed
   qed
 qed
 
+lemma path_compression_3a:
+  assumes "path_compression_invariant p x (p[[w]]) p0 w"
+  shows "p0[p0\<^sup>T\<^sup>\<star> * x\<longmapsto>p[[w]]] = p"
+proof -
+  let ?y = "p[[w]]"
+  let ?p = "p0[p0\<^sup>T\<^sup>\<star> * x\<longmapsto>?y]"
+  have i1: "disjoint_set_forest p" and i2: "point x" and i3: "point ?y" and i4: "?y = root p x"
+    using assms path_compression_invariant_def path_compression_precondition_def by meson+
+  have i5: "point w" and i6: "?y \<le> p\<^sup>T\<^sup>\<star> * w"
+    and i7: "w \<noteq> x \<longrightarrow> p[[x]] = ?y \<and> ?y \<noteq> x \<and> p\<^sup>T\<^sup>+ * w \<le> -x" and i8: "p \<sqinter> 1 = p0 \<sqinter> 1" and i9: "fc p = fc p0"
+    and i10: "root p w = ?y" and i11: "w \<noteq> ?y \<longrightarrow> p[[w]] \<noteq> w" and i12: "p[[w]] = p0[[w]]" and i13: "p0[p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * w)\<longmapsto>?y] = p"
+    and i14: "disjoint_set_forest p0" and i15: "?y = root p0 x" and i16: "w \<le> p0\<^sup>T\<^sup>\<star> * x"
+    using assms path_compression_invariant_def by blast+
+  have 1: "?p \<sqinter> ?y = p \<sqinter> ?y"
+    by (metis i1 i15 i3 i4 get_put inf_le1 root_successor_loop update_inf update_inf_same)
+  have 2: "?p \<sqinter> w = p \<sqinter> w"
+    by (metis i5 i12 i16 get_put update_inf update_inf_same)
+  have "?y = root p0 w"
+    by (metis i1 i10 i14 i8 i9 same_root)
+  hence "p0\<^sup>T\<^sup>\<star> * w = w \<squnion> ?y"
+    by (metis i12 i14 root_transitive_successor_loop star.circ_loop_fixpoint star_plus sup_monoid.add_commute mult_assoc)
+  hence 3: "?p \<sqinter> p0\<^sup>T\<^sup>\<star> * w = p \<sqinter> p0\<^sup>T\<^sup>\<star> * w"
+    using 1 2 by (simp add: inf_sup_distrib1)
+  have "p0\<^sup>T\<^sup>\<star> * w \<le> p0\<^sup>T\<^sup>\<star> * x"
+    by (metis i16 comp_associative mult_right_isotone star.circ_transitive_equal)
+  hence 4: "?p \<sqinter> (p0\<^sup>T\<^sup>\<star> * x \<sqinter> p0\<^sup>T\<^sup>\<star> * w) = p \<sqinter> (p0\<^sup>T\<^sup>\<star> * x \<sqinter> p0\<^sup>T\<^sup>\<star> * w)"
+    using 3 by (simp add: inf.absorb2)
+  have 5: "?p \<sqinter> (p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * w)) = p \<sqinter> (p0\<^sup>T\<^sup>\<star> * x \<sqinter> -(p0\<^sup>T\<^sup>\<star> * w))"
+    by (metis i13 inf_le1 update_inf update_inf_same)
+  have "regular (p0\<^sup>T\<^sup>\<star> * w)"
+    using i14 i5 bijective_regular mapping_regular regular_closed_star regular_conv_closed regular_mult_closed by auto
+  hence 6: "?p \<sqinter> p0\<^sup>T\<^sup>\<star> * x = p \<sqinter> p0\<^sup>T\<^sup>\<star> * x"
+    using 4 5 by (smt inf_sup_distrib1 maddux_3_11_pp)
+  have 7: "?p \<sqinter> -(p0\<^sup>T\<^sup>\<star> * x) = p \<sqinter> -(p0\<^sup>T\<^sup>\<star> * x)"
+    by (smt i13 inf.sup_monoid.add_commute inf_import_p inf_sup_absorb le_iff_inf p_dist_inf update_inf_different inf.idem p_antitone_inf)
+  have "regular (p0\<^sup>T\<^sup>\<star> * x)"
+    using i14 i2 bijective_regular mapping_regular regular_closed_star regular_conv_closed regular_mult_closed by auto
+  thus "?p = p"
+    using 6 7 by (smt inf_sup_distrib1 maddux_3_11_pp)
+qed
+
 lemma path_compression_3:
   "path_compression_invariant p x (p[[w]]) p0 w \<Longrightarrow> path_compression_postcondition p x (p[[w]]) p0"
-  using path_compression_invariant_def path_compression_postcondition_def path_compression_precondition_def by auto
+  using path_compression_invariant_def path_compression_postcondition_def path_compression_precondition_def path_compression_3a by blast
 
 theorem path_compression:
   "VARS p t w
   [ path_compression_precondition p x y \<and> p0 = p ]
   w := x;
   WHILE y \<noteq> p[[w]]
     INV { path_compression_invariant p x y p0 w }
     VAR { card { z . regular z \<and> z \<le> p\<^sup>T\<^sup>\<star> * w } }
      DO t := w;
         w := p[[w]];
         p[t] := y
      OD
   [ path_compression_postcondition p x y p0 ]"
   apply vcg_tc_simp
     apply (fact path_compression_1)
    apply (fact path_compression_2)
   using path_compression_3 by auto
 
 lemma path_compression_exists:
   "path_compression_precondition p x y \<Longrightarrow> \<exists>p' . path_compression_postcondition p' x y p"
   using tc_extract_function path_compression by blast
 
 definition "path_compression p x y \<equiv> (SOME p' . path_compression_postcondition p' x y p)"
 
 lemma path_compression_function:
   assumes "path_compression_precondition p x y"
     and "p' = path_compression p x y"
   shows "path_compression_postcondition p' x y p"
   by (metis assms path_compression_def path_compression_exists someI)
 
 subsection \<open>Find-Set with Path Compression\<close>
 
 text \<open>
 We sequentially combine find-set and path compression.
 We consider implementations which use the previously derived functions and implementations which unfold their definitions.
 \<close>
 
 theorem find_set_path_compression:
   "VARS p y
   [ find_set_precondition p x \<and> p0 = p ]
   y := find_set p x;
   p := path_compression p x y
   [ path_compression_postcondition p x y p0 ]"
   apply vcg_tc_simp
   using find_set_function find_set_postcondition_def find_set_precondition_def path_compression_function path_compression_precondition_def by fastforce
 
 theorem find_set_path_compression_1:
   "VARS p t w y
   [ find_set_precondition p x \<and> p0 = p ]
   y := find_set p x;
   w := x;
   WHILE y \<noteq> p[[w]]
     INV { path_compression_invariant p x y p0 w }
     VAR { card { z . regular z \<and> z \<le> p\<^sup>T\<^sup>\<star> * w } }
      DO t := w;
         w := p[[w]];
         p[t] := y
      OD
   [ path_compression_postcondition p x y p0 ]"
   apply vcg_tc_simp
     using find_set_function find_set_postcondition_def find_set_precondition_def path_compression_1 path_compression_precondition_def apply fastforce
    apply (fact path_compression_2)
   by (fact path_compression_3)
 
 theorem find_set_path_compression_2:
   "VARS p y
   [ find_set_precondition p x \<and> p0 = p ]
   y := x;
   WHILE y \<noteq> p[[y]]
     INV { find_set_invariant p x y \<and> p0 = p }
     VAR { card { z . regular z \<and> z \<le> p\<^sup>T\<^sup>\<star> * y } }
      DO y := p[[y]]
      OD;
   p := path_compression p x y
   [ path_compression_postcondition p x y p0 ]"
   apply vcg_tc_simp
     apply (fact find_set_1)
    apply (fact find_set_2)
   by (smt find_set_3 find_set_invariant_def find_set_postcondition_def find_set_precondition_def path_compression_function path_compression_precondition_def)
 
 theorem find_set_path_compression_3:
   "VARS p t w y
   [ find_set_precondition p x \<and> p0 = p ]
   y := x;
   WHILE y \<noteq> p[[y]]
     INV { find_set_invariant p x y \<and> p0 = p }
     VAR { card { z . regular z \<and> z \<le> p\<^sup>T\<^sup>\<star> * y } }
      DO y := p[[y]]
      OD;
   w := x;
   WHILE y \<noteq> p[[w]]
     INV { path_compression_invariant p x y p0 w }
     VAR { card { z . regular z \<and> z \<le> p\<^sup>T\<^sup>\<star> * w } }
      DO t := w;
         w := p[[w]];
         p[t] := y
      OD
   [ path_compression_postcondition p x y p0 ]"
   apply vcg_tc_simp
       apply (simp add: find_set_1)
      apply (fact find_set_2)
-    using find_set_3 find_set_invariant_def find_set_postcondition_def find_set_precondition_def path_compression_invariant_def path_compression_precondition_def apply blast
+    using find_set_3 find_set_invariant_def find_set_postcondition_def find_set_precondition_def path_compression_1 path_compression_precondition_def apply blast
    apply (fact path_compression_2)
   by (fact path_compression_3)
 
 text \<open>
 Find-set with path compression returns two results: the representative of the tree and the modified disjoint-set forest.
 \<close>
 
 lemma find_set_path_compression_exists:
   "find_set_precondition p x \<Longrightarrow> \<exists>p' y . path_compression_postcondition p' x y p"
   using tc_extract_function find_set_path_compression by blast
 
 definition "find_set_path_compression p x \<equiv> (SOME (p',y) . path_compression_postcondition p' x y p)"
 
 lemma find_set_path_compression_function:
   assumes "find_set_precondition p x"
     and "(p',y) = find_set_path_compression p x"
   shows "path_compression_postcondition p' x y p"
 proof -
   let ?P = "\<lambda>(p',y) . path_compression_postcondition p' x y p"
   have "?P (SOME z . ?P z)"
     apply (unfold some_eq_ex)
     using assms(1) find_set_path_compression_exists by simp
   thus ?thesis
     using assms(2) find_set_path_compression_def by auto
 qed
 
 text \<open>
 We prove that \<open>find_set_path_compression\<close> returns the same representative as \<open>find_set\<close>.
 \<close>
 
 lemma find_set_path_compression_find_set:
   assumes "find_set_precondition p x"
   shows "find_set p x = snd (find_set_path_compression p x)"
 proof -
   let ?r = "find_set p x"
   let ?p = "fst (find_set_path_compression p x)"
   let ?y = "snd (find_set_path_compression p x)"
   have 1: "find_set_postcondition p x ?r"
     by (simp add: assms find_set_function)
   have "path_compression_postcondition ?p x ?y p"
     using assms find_set_path_compression_function prod.collapse by blast
   thus "?r = ?y"
     using 1 by (smt assms same_root find_set_precondition_def find_set_postcondition_def path_compression_precondition_def path_compression_postcondition_def)
 qed
 
 text \<open>
-Proving equality of \<open>path_compression p x (find_set p x)\<close> and \<open>fst (find_set_path_compression p x)\<close> would need a stronger postcondition of path compression describing the precise effect of how links change.
-However we can prove that the two forests have the same semantics; that is, they describe the same disjoint sets and have the same roots.
+A weaker postcondition suffices to prove that the two forests have the same semantics; that is, they describe the same disjoint sets and have the same roots.
 \<close>
 
 lemma find_set_path_compression_path_compression_semantics:
   assumes "find_set_precondition p x"
   shows "fc (path_compression p x (find_set p x)) = fc (fst (find_set_path_compression p x))"
     and "path_compression p x (find_set p x) \<sqinter> 1 = fst (find_set_path_compression p x) \<sqinter> 1"
 proof -
   let ?r = "find_set p x"
   let ?q = "path_compression p x ?r"
   let ?p = "fst (find_set_path_compression p x)"
   let ?y = "snd (find_set_path_compression p x)"
   have 1: "path_compression_postcondition (path_compression p x ?r) x ?r p"
     using assms find_set_function find_set_postcondition_def find_set_precondition_def path_compression_function path_compression_precondition_def by auto
   have 2: "path_compression_postcondition ?p x ?y p"
     using assms find_set_path_compression_function prod.collapse by blast
   show "fc ?q = fc ?p"
     using 1 2 by (simp add: path_compression_postcondition_def)
   show "?q \<sqinter> 1 = ?p \<sqinter> 1"
     using 1 2 by (simp add: path_compression_postcondition_def)
 qed
 
+text \<open>
+With the current, stronger postcondition of path compression describing the precise effect of how links change, we can prove that the two forests are actually equal.
+\<close>
+
+lemma find_set_path_compression_find_set_pathcompression:
+  assumes "find_set_precondition p x"
+  shows "path_compression p x (find_set p x) = fst (find_set_path_compression p x)"
+proof -
+  let ?r = "find_set p x"
+  let ?q = "path_compression p x ?r"
+  let ?p = "fst (find_set_path_compression p x)"
+  let ?y = "snd (find_set_path_compression p x)"
+  have 1: "path_compression_postcondition (path_compression p x ?r) x ?r p"
+    using assms find_set_function find_set_postcondition_def find_set_precondition_def path_compression_function path_compression_precondition_def by auto
+  have 2: "path_compression_postcondition ?p x ?y p"
+    using assms find_set_path_compression_function prod.collapse by blast
+  have "?r = ?y"
+    by (simp add: assms find_set_path_compression_find_set)
+  thus "?q = ?p"
+    using 1 2 by (simp add: path_compression_postcondition_def)
+qed
+
 subsection \<open>Union-Sets\<close>
 
 text \<open>
 We only consider a naive union-sets operation (without ranks).
 The semantics is the equivalence closure obtained after adding the link between the two given nodes, 
 which requires those two elements to be in the same set.
 The implementation uses temporary variable \<open>t\<close> to store the two results returned by find-set with path compression.
 The disjoint-set forest, which keeps being updated, is threaded through the sequence of operations.
 \<close>
 
 definition "union_sets_precondition p x y \<equiv> disjoint_set_forest p \<and> point x \<and> point y"
 definition "union_sets_postcondition p x y p0 \<equiv> union_sets_precondition p x y \<and> fc p = wcc (p0 \<squnion> x * y\<^sup>T)"
 
 lemma union_sets_1:
   assumes "union_sets_precondition p0 x y"
     and "path_compression_postcondition p1 x r p0"
     and "path_compression_postcondition p2 y s p1"
   shows "union_sets_postcondition (p2[r\<longmapsto>s]) x y p0"
 proof (unfold union_sets_postcondition_def union_sets_precondition_def, intro conjI)
   let ?p = "p2[r\<longmapsto>s]"
   have 1: "disjoint_set_forest p1 \<and> point r \<and> r = root p1 x \<and> p1 \<sqinter> 1 = p0 \<sqinter> 1 \<and> fc p1 = fc p0"
     using assms(2) path_compression_precondition_def path_compression_postcondition_def by auto
   have 2: "disjoint_set_forest p2 \<and> point s \<and> s = root p2 y \<and> p2 \<sqinter> 1 = p1 \<sqinter> 1 \<and> fc p2 = fc p1"
     using assms(3) path_compression_precondition_def path_compression_postcondition_def by auto
   hence 3: "fc p2 = fc p0"
     using 1 by simp
   show 4: "univalent ?p"
     using 1 2 update_univalent by blast
   show "total ?p"
     using 1 2 bijective_regular update_total by blast
   show "acyclic (?p \<sqinter> -1)"
   proof (cases "r = s")
     case True
     thus ?thesis
-      using 2 update_acyclic_3 by fastforce
+      using 2 update_acyclic_5 by fastforce
   next
     case False
     hence "bot = r \<sqinter> s"
       using 1 2 distinct_points by blast
     also have "... = r \<sqinter> p2\<^sup>T\<^sup>\<star> * s"
       using 2 by (smt root_transitive_successor_loop)
     finally have "s \<sqinter> p2\<^sup>\<star> * r = bot"
       using schroeder_1 conv_star_commute inf.sup_monoid.add_commute by fastforce
     thus ?thesis
-      using 1 2 update_acyclic_2 by blast
+      using 1 2 update_acyclic_4 by blast
   qed
   show "vector x"
     using assms(1) by (simp add: union_sets_precondition_def)
   show "injective x"
     using assms(1) by (simp add: union_sets_precondition_def)
   show "surjective x"
     using assms(1) by (simp add: union_sets_precondition_def)
   show "vector y"
     using assms(1) by (simp add: union_sets_precondition_def)
   show "injective y"
     using assms(1) by (simp add: union_sets_precondition_def)
   show "surjective y"
     using assms(1) by (simp add: union_sets_precondition_def)
   show "fc ?p = wcc (p0 \<squnion> x * y\<^sup>T)"
   proof (rule antisym)
     have "r = p1[[r]]"
       using 1 by (metis root_successor_loop)
     hence "r * r\<^sup>T \<le> p1\<^sup>T"
       using 1 eq_refl shunt_bijective by blast
     hence "r * r\<^sup>T \<le> p1"
       using 1 conv_order coreflexive_symmetric by fastforce
     hence "r * r\<^sup>T \<le> p1 \<sqinter> 1"
       using 1 inf.boundedI by blast
     also have "... = p2 \<sqinter> 1"
       using 2 by simp
     finally have "r * r\<^sup>T \<le> p2"
       by simp
     hence "r \<le> p2 * r"
       using 1 shunt_bijective by blast
     hence 5: "p2[[r]] \<le> r"
       using 2 shunt_mapping by blast
     have "r \<sqinter> p2 \<le> r * (top \<sqinter> r\<^sup>T * p2)"
       using 1 by (metis dedekind_1)
     also have "... = r * r\<^sup>T * p2"
       by (simp add: mult_assoc)
     also have "... \<le> r * r\<^sup>T"
       using 5 by (metis comp_associative conv_dist_comp conv_involutive conv_order mult_right_isotone)
     also have "... \<le> 1"
       using 1 by blast
     finally have 6: "r \<sqinter> p2 \<le> 1"
       by simp
     have "p0 \<le> wcc p0"
       by (simp add: star.circ_sub_dist_1)
     also have "... = wcc p2"
       using 3 by (simp add: star_decompose_1)
     also have 7: "... \<le> wcc ?p"
     proof -
       have "wcc p2 = wcc ((-r \<sqinter> p2) \<squnion> (r \<sqinter> p2))"
         using 1 by (metis bijective_regular inf.sup_monoid.add_commute maddux_3_11_pp)
       also have "... \<le> wcc ((-r \<sqinter> p2) \<squnion> 1)"
         using 6 wcc_isotone sup_right_isotone by simp
       also have "... = wcc (-r \<sqinter> p2)"
         using wcc_with_loops by simp
       also have "... \<le> wcc ?p"
         using wcc_isotone sup_ge2 by blast
       finally show ?thesis
         by simp
     qed
     finally have 8: "p0 \<le> wcc ?p"
       by force
     have "r \<le> p1\<^sup>T\<^sup>\<star> * x"
       using 1 by (metis inf_le1)
     hence 9: "r * x\<^sup>T \<le> p1\<^sup>T\<^sup>\<star>"
       using assms(1) shunt_bijective union_sets_precondition_def by blast
     hence "x * r\<^sup>T \<le> p1\<^sup>\<star>"
       using conv_dist_comp conv_order conv_star_commute by force
     also have "... \<le> wcc p1"
       by (simp add: star.circ_sub_dist)
     also have "... = wcc p2"
       using 1 2 by (simp add: fc_wcc)
     also have "... \<le> wcc ?p"
       using 7 by simp
     finally have 10: "x * r\<^sup>T \<le> wcc ?p"
       by simp
     have 11: "r * s\<^sup>T \<le> wcc ?p"
       using 1 2 star.circ_sub_dist_1 sup_assoc vector_covector by auto
     have "s \<le> p2\<^sup>T\<^sup>\<star> * y"
       using 2 by (metis inf_le1)
     hence 12: "s * y\<^sup>T \<le> p2\<^sup>T\<^sup>\<star>"
       using assms(1) shunt_bijective union_sets_precondition_def by blast
     also have "... \<le> wcc p2"
       using star_isotone sup_ge2 by blast
     also have "... \<le> wcc ?p"
       using 7 by simp
     finally have 13: "s * y\<^sup>T \<le> wcc ?p"
       by simp
     have "x \<le> x * r\<^sup>T * r \<and> y \<le> y * s\<^sup>T * s"
       using 1 2 shunt_bijective by blast
     hence "x * y\<^sup>T \<le> x * r\<^sup>T * r * (y * s\<^sup>T * s)\<^sup>T"
       using comp_isotone conv_isotone by blast
     also have "... = x * r\<^sup>T * r * s\<^sup>T * s * y\<^sup>T"
       by (simp add: comp_associative conv_dist_comp)
     also have "... \<le> wcc ?p * (r * s\<^sup>T) * (s * y\<^sup>T)"
       using 10 by (metis mult_left_isotone mult_assoc)
     also have "... \<le> wcc ?p * wcc ?p * (s * y\<^sup>T)"
       using 11 by (metis mult_left_isotone mult_right_isotone)
     also have "... \<le> wcc ?p * wcc ?p * wcc ?p"
       using 13 by (metis mult_right_isotone)
     also have "... = wcc ?p"
       by (simp add: star.circ_transitive_equal)
     finally have "p0 \<squnion> x * y\<^sup>T \<le> wcc ?p"
       using 8 by simp
     hence "wcc (p0 \<squnion> x * y\<^sup>T) \<le> wcc ?p"
       using wcc_below_wcc by simp
     thus "wcc (p0 \<squnion> x * y\<^sup>T) \<le> fc ?p"
       using 4 fc_wcc by simp
     have "-r \<sqinter> p2 \<le> wcc p2"
       by (simp add: inf.coboundedI2 star.circ_sub_dist_1)
     also have "... = wcc p0"
       using 3 by (simp add: star_decompose_1)
     also have "... \<le> wcc (p0 \<squnion> x * y\<^sup>T)"
       by (simp add: wcc_isotone)
     finally have 14: "-r \<sqinter> p2 \<le> wcc (p0 \<squnion> x * y\<^sup>T)"
       by simp
     have "r * x\<^sup>T \<le> wcc p1"
       using 9 inf.order_trans star.circ_sub_dist sup_commute by fastforce
     also have "... = wcc p0"
       using 1 by (simp add: star_decompose_1)
     also have "... \<le> wcc (p0 \<squnion> x * y\<^sup>T)"
       by (simp add: wcc_isotone)
     finally have 15: "r * x\<^sup>T \<le> wcc (p0 \<squnion> x * y\<^sup>T)"
       by simp
     have 16: "x * y\<^sup>T \<le> wcc (p0 \<squnion> x * y\<^sup>T)"
       using le_supE star.circ_sub_dist_1 by blast
     have "y * s\<^sup>T \<le> p2\<^sup>\<star>"
       using 12 conv_dist_comp conv_order conv_star_commute by fastforce
     also have "... \<le> wcc p2"
       using star.circ_sub_dist sup_commute by fastforce
     also have "... = wcc p0"
       using 3 by (simp add: star_decompose_1)
     also have "... \<le> wcc (p0 \<squnion> x * y\<^sup>T)"
       by (simp add: wcc_isotone)
     finally have 17: "y * s\<^sup>T \<le> wcc (p0 \<squnion> x * y\<^sup>T)"
       by simp
     have "r \<le> r * x\<^sup>T * x \<and> s \<le> s * y\<^sup>T * y"
       using assms(1) shunt_bijective union_sets_precondition_def by blast
     hence "r * s\<^sup>T \<le> r * x\<^sup>T * x * (s * y\<^sup>T * y)\<^sup>T"
       using comp_isotone conv_isotone by blast
     also have "... = r * x\<^sup>T * x * y\<^sup>T * y * s\<^sup>T"
       by (simp add: comp_associative conv_dist_comp)
     also have "... \<le> wcc (p0 \<squnion> x * y\<^sup>T) * (x * y\<^sup>T) * (y * s\<^sup>T)"
       using 15 by (metis mult_left_isotone mult_assoc)
     also have "... \<le> wcc (p0 \<squnion> x * y\<^sup>T) * wcc (p0 \<squnion> x * y\<^sup>T) * (y * s\<^sup>T)"
       using 16 by (metis mult_left_isotone mult_right_isotone)
     also have "... \<le> wcc (p0 \<squnion> x * y\<^sup>T) * wcc (p0 \<squnion> x * y\<^sup>T) * wcc (p0 \<squnion> x * y\<^sup>T)"
       using 17 by (metis mult_right_isotone)
     also have "... = wcc (p0 \<squnion> x * y\<^sup>T)"
       by (simp add: star.circ_transitive_equal)
     finally have "?p \<le> wcc (p0 \<squnion> x * y\<^sup>T)"
       using 1 2 14 vector_covector by auto
     hence "wcc ?p \<le> wcc (p0 \<squnion> x * y\<^sup>T)"
       using wcc_below_wcc by blast
     thus "fc ?p \<le> wcc (p0 \<squnion> x * y\<^sup>T)"
       using 4 fc_wcc by simp
   qed
 qed
 
 theorem union_sets:
   "VARS p r s t
   [ union_sets_precondition p x y \<and> p0 = p ]
   t := find_set_path_compression p x;
   p := fst t;
   r := snd t;
   t := find_set_path_compression p y;
   p := fst t;
   s := snd t;
   p[r] := s
   [ union_sets_postcondition p x y p0 ]"
 proof vcg_tc_simp
   let ?t1 = "find_set_path_compression p0 x"
   let ?p1 = "fst ?t1"
   let ?r = "snd ?t1"
   let ?t2 = "find_set_path_compression ?p1 y"
   let ?p2 = "fst ?t2"
   let ?s = "snd ?t2"
   let ?p = "?p2[?r\<longmapsto>?s]"
   assume 1: "union_sets_precondition p0 x y"
   hence 2: "path_compression_postcondition ?p1 x ?r p0"
     by (simp add: find_set_precondition_def union_sets_precondition_def find_set_path_compression_function)
   hence "path_compression_postcondition ?p2 y ?s ?p1"
     using 1 by (meson find_set_precondition_def union_sets_precondition_def find_set_path_compression_function path_compression_postcondition_def path_compression_precondition_def prod.collapse)
   thus "union_sets_postcondition (?p2[?r\<longmapsto>?s]) x y p0"
     using 1 2 by (simp add: union_sets_1)
 qed
 
 lemma union_sets_exists:
   "union_sets_precondition p x y \<Longrightarrow> \<exists>p' . union_sets_postcondition p' x y p"
   using tc_extract_function union_sets by blast
 
 definition "union_sets p x y \<equiv> (SOME p' . union_sets_postcondition p' x y p)"
 
 lemma union_sets_function:
   assumes "union_sets_precondition p x y"
     and "p' = union_sets p x y"
   shows "union_sets_postcondition p' x y p"
   by (metis assms union_sets_def union_sets_exists someI)
 
 theorem union_sets_2:
   "VARS p r s t
   [ union_sets_precondition p x y \<and> p0 = p ]
   r := find_set p x;
   p := path_compression p x r;
   s := find_set p y;
   p := path_compression p y s;
   p[r] := s
   [ union_sets_postcondition p x y p0 ]"
 proof vcg_tc_simp
   let ?r = "find_set p0 x"
   let ?p1 = "path_compression p0 x ?r"
   let ?s = "find_set ?p1 y"
   let ?p2 = "path_compression ?p1 y ?s"
   assume 1: "union_sets_precondition p0 x y"
   hence 2: "path_compression_postcondition ?p1 x ?r p0"
     using find_set_function find_set_postcondition_def find_set_precondition_def path_compression_function path_compression_precondition_def union_sets_precondition_def by auto
   hence "path_compression_postcondition ?p2 y ?s ?p1"
     using 1 find_set_function find_set_postcondition_def find_set_precondition_def path_compression_function path_compression_precondition_def union_sets_precondition_def path_compression_postcondition_def by meson
   thus "union_sets_postcondition (?p2[?r\<longmapsto>?s]) x y p0"
     using 1 2 by (simp add: union_sets_1)
 qed
 
 end
 
 end