Theory Graph (Isabelle2005: October 2005)

# Theory Graph

Up to index of Isabelle/HOL/HoareParallel

theory Graph
imports Main
begin

    header {* \chapter{Case Study: Single and Multi-Mutator Garbage Collection Algorithms}

    \section {Formalization of the Memory} *}

    theory Graph imports Main begin

    datatype node = Black | White

    types
      nodes = "node list"
      edge  = "nat × nat"
      edges = "edge list"

    consts Roots :: "nat set"

    constdefs
      Proper_Roots :: "nodes => bool"
      "Proper_Roots M ≡ Roots≠{} ∧ Roots ⊆ {i. i<length M}"

      Proper_Edges :: "(nodes × edges) => bool"
      "Proper_Edges ≡ (λ(M,E). ∀i<length E. fst(E!i)<length M ∧ snd(E!i)<length M)"

      BtoW :: "(edge × nodes) => bool"
      "BtoW ≡ (λ(e,M). (M!fst e)=Black ∧ (M!snd e)≠Black)"

      Blacks :: "nodes => nat set"
      "Blacks M ≡ {i. i<length M ∧ M!i=Black}"

      Reach :: "edges => nat set"
      "Reach E ≡ {x. (∃path. 1<length path ∧ path!(length path - 1)∈Roots ∧ x=path!0
                  ∧ (∀i<length path - 1. (∃j<length E. E!j=(path!(i+1), path!i))))
                  ∨ x∈Roots}"

    text{* Reach: the set of reachable nodes is the set of Roots together with the
    nodes reachable from some Root by a path represented by a list of
      nodes (at least two since we traverse at least one edge), where two
    consecutive nodes correspond to an edge in E. *}

    subsection {* Proofs about Graphs *}

    lemmas Graph_defs= Blacks_def Proper_Roots_def Proper_Edges_def BtoW_def
    declare Graph_defs [simp]

    subsubsection{* Graph 1 *}

    lemma Graph1_aux [rule_format]:
      "[| Roots⊆Blacks M; ∀i<length E. ¬BtoW(E!i,M)|]
      ==> 1< length path --> (path!(length path - 1))∈Roots -->
      (∀i<length path - 1. (∃j. j < length E ∧ E!j=(path!(Suc i), path!i)))
      --> M!(path!0) = Black"
    apply(induct_tac "path")
     apply force
    apply clarify
    apply simp
    apply(case_tac "list")
     apply force
    apply simp
    apply(rotate_tac -2)
    apply(erule_tac x = "0" in all_dupE)
    apply simp
    apply clarify
    apply(erule allE , erule (1) notE impE)
    apply simp
    apply(erule mp)
    apply(case_tac "lista")
     apply force
    apply simp
    apply(erule mp)
    apply clarify
    apply(erule_tac x = "Suc i" in allE)
    apply force
    done

    lemma Graph1:
      "[|Roots⊆Blacks M; Proper_Edges(M, E); ∀i<length E. ¬BtoW(E!i,M) |]
      ==> Reach E⊆Blacks M"
    apply (unfold Reach_def)
    apply simp
    apply clarify
    apply(erule disjE)
     apply clarify
     apply(rule conjI)
      apply(subgoal_tac "0< length path - Suc 0")
       apply(erule allE , erule (1) notE impE)
       apply force
      apply simp
     apply(rule Graph1_aux)
    apply auto
    done

    subsubsection{* Graph 2 *}

    lemma Ex_first_occurrence [rule_format]:
      "P (n::nat) --> (∃m. P m ∧ (∀i. i<m --> ¬ P i))";
    apply(rule nat_less_induct)
    apply clarify
    apply(case_tac "∀m. m<n --> ¬ P m")
    apply auto
    done

    lemma Compl_lemma: "(n::nat)≤l ==> (∃m. m≤l ∧ n=l - m)"
    apply(rule_tac x = "l - n" in exI)
    apply arith
    done

    lemma Ex_last_occurrence:
      "[|P (n::nat); n≤l|] ==> (∃m. P (l - m) ∧ (∀i. i<m --> ¬P (l - i)))"
    apply(drule Compl_lemma)
    apply clarify
    apply(erule Ex_first_occurrence)
    done

    lemma Graph2:
      "[|T ∈ Reach E; R<length E|] ==> T ∈ Reach (E[R:=(fst(E!R), T)])"
    apply (unfold Reach_def)
    apply clarify
    apply simp
    apply(case_tac "∀z<length path. fst(E!R)≠path!z")
     apply(rule_tac x = "path" in exI)
     apply simp
     apply clarify
     apply(erule allE , erule (1) notE impE)
     apply clarify
     apply(rule_tac x = "j" in exI)
     apply(case_tac "j=R")
      apply(erule_tac x = "Suc i" in allE)
      apply simp
      apply arith
     apply (force simp add:nth_list_update)
    apply simp
    apply(erule exE)
    apply(subgoal_tac "z ≤ length path - Suc 0")
     prefer 2 apply arith
    apply(drule_tac P = "λm. m<length path ∧ fst(E!R)=path!m" in Ex_last_occurrence)
     apply assumption
    apply clarify
    apply simp
    apply(rule_tac x = "(path!0)#(drop (length path - Suc m) path)" in exI)
    apply simp
    apply(case_tac "length path - (length path - Suc m)")
     apply arith
    apply simp
    apply(subgoal_tac "(length path - Suc m) + nat ≤ length path")
     prefer 2 apply arith
    apply(drule nth_drop)
    apply simp
    apply(subgoal_tac "length path - Suc m + nat = length path - Suc 0")
     prefer 2 apply arith
    apply simp
    apply clarify
    apply(case_tac "i")
     apply(force simp add: nth_list_update)
    apply simp
    apply(subgoal_tac "(length path - Suc m) + nata ≤ length path")
     prefer 2 apply arith
    apply simp
    apply(subgoal_tac "(length path - Suc m) + (Suc nata) ≤ length path")
     prefer 2 apply arith
    apply simp
    apply(erule_tac x = "length path - Suc m + nata" in allE)
    apply simp
    apply clarify
    apply(rule_tac x = "j" in exI)
    apply(case_tac "R=j")
     prefer 2 apply force
    apply simp
    apply(drule_tac t = "path ! (length path - Suc m)" in sym)
    apply simp
    apply(case_tac " length path - Suc 0 < m")
     apply(subgoal_tac "(length path - Suc m)=0")
      prefer 2 apply arith
     apply(simp del: diff_is_0_eq)
     apply(subgoal_tac "Suc nata≤nat")
     prefer 2 apply arith
     apply(drule_tac n = "Suc nata" in Compl_lemma)
     apply clarify
     apply force
    apply(drule leI)
    apply(subgoal_tac "Suc (length path - Suc m + nata)=(length path - Suc 0) - (m - Suc nata)")
     apply(erule_tac x = "m - (Suc nata)" in allE)
     apply(case_tac "m")
      apply simp
     apply simp
     apply(subgoal_tac "natb - nata < Suc natb")
      prefer 2 apply(erule thin_rl)+ apply arith
     apply simp
     apply(case_tac "length path")
      apply force
    apply (erule_tac V = "Suc natb ≤ length path - Suc 0" in thin_rl)
    apply simp
    apply(frule_tac i1 = "length path" and j1 = "length path - Suc 0" and k1 = "m" in diff_diff_right [THEN mp])
    apply(erule_tac V = "length path - Suc m + nat = length path - Suc 0" in thin_rl)
    apply simp
    apply arith
    done

    subsubsection{* Graph 3 *}

    lemma Graph3:
      "[| T∈Reach E; R<length E |] ==> Reach(E[R:=(fst(E!R),T)]) ⊆ Reach E"
    apply (unfold Reach_def)
    apply clarify
    apply simp
    apply(case_tac "∃i<length path - 1. (fst(E!R),T)=(path!(Suc i),path!i)")
    --{* the changed edge is part of the path *}
     apply(erule exE)
     apply(drule_tac P = "λi. i<length path - 1 ∧ (fst(E!R),T)=(path!Suc i,path!i)" in Ex_first_occurrence)
     apply clarify
     apply(erule disjE)
    --{* T is NOT a root *}
      apply clarify
      apply(rule_tac x = "(take m path)@patha" in exI)
      apply(subgoal_tac "¬(length path≤m)")
       prefer 2 apply arith
      apply(simp add: min_def)
      apply(rule conjI)
       apply(subgoal_tac "¬(m + length patha - 1 < m)")
        prefer 2 apply arith
       apply(simp add: nth_append min_def)
      apply(rule conjI)
       apply(case_tac "m")
        apply force
       apply(case_tac "path")
        apply force
       apply force
      apply clarify
      apply(case_tac "Suc i≤m")
       apply(erule_tac x = "i" in allE)
       apply simp
       apply clarify
       apply(rule_tac x = "j" in exI)
       apply(case_tac "Suc i<m")
        apply(simp add: nth_append min_def)
        apply(case_tac "R=j")
         apply(simp add: nth_list_update)
         apply(case_tac "i=m")
          apply force
         apply(erule_tac x = "i" in allE)
         apply force
        apply(force simp add: nth_list_update)
       apply(simp add: nth_append min_def)
       apply(subgoal_tac "i=m - 1")
        prefer 2 apply arith
       apply(case_tac "R=j")
        apply(erule_tac x = "m - 1" in allE)
        apply(simp add: nth_list_update)
       apply(force simp add: nth_list_update)
      apply(simp add: nth_append min_def)
      apply(rotate_tac -4)
      apply(erule_tac x = "i - m" in allE)
      apply(subgoal_tac "Suc (i - m)=(Suc i - m)" )
        prefer 2 apply arith
       apply simp
      apply(erule mp)
      apply arith
    --{* T is a root *}
     apply(case_tac "m=0")
      apply force
     apply(rule_tac x = "take (Suc m) path" in exI)
     apply(subgoal_tac "¬(length path≤Suc m)" )
      prefer 2 apply arith
     apply(simp add: min_def)
     apply clarify
     apply(erule_tac x = "i" in allE)
     apply simp
     apply clarify
     apply(case_tac "R=j")
      apply(force simp add: nth_list_update)
     apply(force simp add: nth_list_update)
    --{* the changed edge is not part of the path *}
    apply(rule_tac x = "path" in exI)
    apply simp
    apply clarify
    apply(erule_tac x = "i" in allE)
    apply clarify
    apply(case_tac "R=j")
     apply(erule_tac x = "i" in allE)
     apply simp
    apply(force simp add: nth_list_update)
    done

    subsubsection{* Graph 4 *}

    lemma Graph4:
      "[|T ∈ Reach E; Roots⊆Blacks M; I≤length E; T<length M; R<length E;
      ∀i<I. ¬BtoW(E!i,M); R<I; M!fst(E!R)=Black; M!T≠Black|] ==>
      (∃r. I≤r ∧ r<length E ∧ BtoW(E[R:=(fst(E!R),T)]!r,M))"
    apply (unfold Reach_def)
    apply simp
    apply(erule disjE)
     prefer 2 apply force
    apply clarify
    --{* there exist a black node in the path to T *}
    apply(case_tac "∃m<length path. M!(path!m)=Black")
     apply(erule exE)
     apply(drule_tac P = "λm. m<length path ∧ M!(path!m)=Black" in Ex_first_occurrence)
     apply clarify
     apply(case_tac "ma")
      apply force
     apply simp
     apply(case_tac "length path")
      apply force
     apply simp
     apply(erule_tac P = "λi. i < nata --> ?P i" and x = "nat" in allE)
     apply simp
     apply clarify
     apply(erule_tac P = "λi. i < Suc nat --> ?P i" and x = "nat" in allE)
     apply simp
     apply(case_tac "j<I")
      apply(erule_tac x = "j" in allE)
      apply force
     apply(rule_tac x = "j" in exI)
     apply(force  simp add: nth_list_update)
    apply simp
    apply(rotate_tac -1)
    apply(erule_tac x = "length path - 1" in allE)
    apply(case_tac "length path")
     apply force
    apply force
    done

    subsubsection {* Graph 5 *}

    lemma Graph5:
      "[| T ∈ Reach E ; Roots ⊆ Blacks M; ∀i<R. ¬BtoW(E!i,M); T<length M;
        R<length E; M!fst(E!R)=Black; M!snd(E!R)=Black; M!T ≠ Black|]
       ==> (∃r. R<r ∧ r<length E ∧ BtoW(E[R:=(fst(E!R),T)]!r,M))"
    apply (unfold Reach_def)
    apply simp
    apply(erule disjE)
     prefer 2 apply force
    apply clarify
    --{* there exist a black node in the path to T*}
    apply(case_tac "∃m<length path. M!(path!m)=Black")
     apply(erule exE)
     apply(drule_tac P = "λm. m<length path ∧ M!(path!m)=Black" in Ex_first_occurrence)
     apply clarify
     apply(case_tac "ma")
      apply force
     apply simp
     apply(case_tac "length path")
      apply force
     apply simp
     apply(erule_tac P = "λi. i < nata --> ?P i" and x = "nat" in allE)
     apply simp
     apply clarify
     apply(erule_tac P = "λi. i < Suc nat --> ?P i" and x = "nat" in allE)
     apply simp
     apply(case_tac "j≤R")
      apply(drule le_imp_less_or_eq)
      apply(erule disjE)
       apply(erule allE , erule (1) notE impE)
       apply force
      apply force
     apply(rule_tac x = "j" in exI)
     apply(force  simp add: nth_list_update)
    apply simp
    apply(rotate_tac -1)
    apply(erule_tac x = "length path - 1" in allE)
    apply(case_tac "length path")
     apply force
    apply force
    done

    subsubsection {* Other lemmas about graphs *}

    lemma Graph6:
     "[|Proper_Edges(M,E); R<length E ; T<length M|] ==> Proper_Edges(M,E[R:=(fst(E!R),T)])"
    apply (unfold Proper_Edges_def)
     apply(force  simp add: nth_list_update)
    done

    lemma Graph7:
     "[|Proper_Edges(M,E)|] ==> Proper_Edges(M[T:=a],E)"
    apply (unfold Proper_Edges_def)
    apply force
    done

    lemma Graph8:
     "[|Proper_Roots(M)|] ==> Proper_Roots(M[T:=a])"
    apply (unfold Proper_Roots_def)
    apply force
    done

    text{* Some specific lemmata for the verification of garbage collection algorithms. *}

    lemma Graph9: "j<length M ==> Blacks M⊆Blacks (M[j := Black])"
    apply (unfold Blacks_def)
     apply(force simp add: nth_list_update)
    done

    lemma Graph10 [rule_format (no_asm)]: "∀i. M!i=a -->M[i:=a]=M"
    apply(induct_tac "M")
    apply auto
    apply(case_tac "i")
    apply auto
    done

    lemma Graph11 [rule_format (no_asm)]:
      "[| M!j≠Black;j<length M|] ==> Blacks M ⊂ Blacks (M[j := Black])"
    apply (unfold Blacks_def)
    apply(rule psubsetI)
     apply(force simp add: nth_list_update)
    apply safe
    apply(erule_tac c = "j" in equalityCE)
    apply auto
    done

    lemma Graph12: "[|a⊆Blacks M;j<length M|] ==> a⊆Blacks (M[j := Black])"
    apply (unfold Blacks_def)
    apply(force simp add: nth_list_update)
    done

    lemma Graph13: "[|a⊂ Blacks M;j<length M|] ==> a ⊂ Blacks (M[j := Black])"
    apply (unfold Blacks_def)
    apply(erule psubset_subset_trans)
    apply(force simp add: nth_list_update)
    done

    declare Graph_defs [simp del]

    end

### Proofs about Graphs

lemmas Graph_defs:

      Blacks M == {i. i < length M ∧ M ! i = Black}

      Proper_Roots M == Roots ≠ {} ∧ Roots ⊆ {i. i < length M}

      Proper_Edges ==
      %(M, E). ∀i<length E. fst (E ! i) < length M ∧ snd (E ! i) < length M

      BtoW == %(e, M). M ! fst e = Black ∧ M ! snd e ≠ Black

lemmas Graph_defs:

      Blacks M == {i. i < length M ∧ M ! i = Black}

      Proper_Roots M == Roots ≠ {} ∧ Roots ⊆ {i. i < length M}

      Proper_Edges ==
      %(M, E). ∀i<length E. fst (E ! i) < length M ∧ snd (E ! i) < length M

      BtoW == %(e, M). M ! fst e = Black ∧ M ! snd e ≠ Black

#### Graph 1

lemma Graph1_aux:

      [| Roots ⊆ Blacks M; !!i. i < length E ==> ¬ BtoW (E ! i, M); 1 < length path;
         path ! (length path - 1) ∈ Roots;
         !!i. i < length path - 1 ==> ∃j<length E. E ! j = (path ! Suc i, path ! i) |]
      ==> M ! (path ! 0) = Black

lemma Graph1:

      [| Roots ⊆ Blacks M; Proper_Edges (M, E); ∀i<length E. ¬ BtoW (E ! i, M) |]
      ==> Reach E ⊆ Blacks M

#### Graph 2

lemma Ex_first_occurrence:

      P n ==> ∃m. P m ∧ (∀i<m. ¬ P i)

lemma Compl_lemma:

      n ≤ l ==> ∃m≤l. n = l - m

lemma Ex_last_occurrence:

      [| P n; n ≤ l |] ==> ∃m. P (l - m) ∧ (∀i<m. ¬ P (l - i))

lemma Graph2:

      [| T ∈ Reach E; R < length E |] ==> T ∈ Reach (E[R := (fst (E ! R), T)])

#### Graph 3

lemma Graph3:

      [| T ∈ Reach E; R < length E |] ==> Reach (E[R := (fst (E ! R), T)]) ⊆ Reach E

#### Graph 4

lemma Graph4:

      [| T ∈ Reach E; Roots ⊆ Blacks M; I ≤ length E; T < length M; R < length E;
         ∀i<I. ¬ BtoW (E ! i, M); R < I; M ! fst (E ! R) = Black; M ! T ≠ Black |]
      ==> ∃r≥I. r < length E ∧ BtoW (E[R := (fst (E ! R), T)] ! r, M)

#### Graph 5

lemma Graph5:

      [| T ∈ Reach E; Roots ⊆ Blacks M; ∀i<R. ¬ BtoW (E ! i, M); T < length M;
         R < length E; M ! fst (E ! R) = Black; M ! snd (E ! R) = Black;
         M ! T ≠ Black |]
      ==> ∃r>R. r < length E ∧ BtoW (E[R := (fst (E ! R), T)] ! r, M)

#### Other lemmas about graphs

lemma Graph6:

      [| Proper_Edges (M, E); R < length E; T < length M |]
      ==> Proper_Edges (M, E[R := (fst (E ! R), T)])

lemma Graph7:

      Proper_Edges (M, E) ==> Proper_Edges (M[T := a], E)

lemma Graph8:

      Proper_Roots M ==> Proper_Roots (M[T := a])

lemma Graph9:

      j < length M ==> Blacks M ⊆ Blacks (M[j := Black])

lemma Graph10:

      M ! i = a ==> M[i := a] = M

lemma Graph11:

      [| M ! j ≠ Black; j < length M |] ==> Blacks M ⊂ Blacks (M[j := Black])

lemma Graph12:

      [| a ⊆ Blacks M; j < length M |] ==> a ⊆ Blacks (M[j := Black])

lemma Graph13:

      [| a ⊂ Blacks M; j < length M |] ==> a ⊂ Blacks (M[j := Black])