Theory Kildall

(*  Title:      HOL/MicroJava/BV/Kildall.thy
    ID:         $Id: Kildall.html 1910 2004-05-19 04:46:04Z kleing $
    Author:     Tobias Nipkow, Gerwin Klein
    Copyright   2000 TUM

Kildall's algorithm
*)

header {* \isaheader{Kildall's Algorithm}\label{sec:Kildall} *}

theory Kildall = SemilatAlg:


consts
 iter :: "'s binop => 's step_type =>
          's list => nat set => 's list × nat set"
 propa :: "'s binop => (nat × 's) list => 's list => nat set => 's list * nat set"

primrec
"propa f []      τs w = (τs,w)"
"propa f (q'#qs) τs w = (let (q,τ) = q';
                             u = τ \<squnion>f τs!q;
                             w' = (if u = τs!q then w else insert q w)
                         in propa f qs (τs[q := u]) w')"

defs iter_def:
"iter f step τs w ≡
 while (λ(τs,w). w ≠ {})
       (λ(τs,w). let p = SOME p. p ∈ w
                 in propa f (step p (τs!p)) τs (w-{p}))
       (τs,w)"

constdefs
 unstables :: "'s ord => 's step_type => 's list => nat set"
"unstables r step τs ≡ {p. p < size τs ∧ ¬stable r step τs p}"

 kildall :: "'s ord => 's binop => 's step_type => 's list => 's list"
"kildall r f step τs ≡ fst(iter f step τs (unstables r step τs))"

consts merges :: "'s binop => (nat × 's) list => 's list => 's list"
primrec
"merges f []      τs = τs"
"merges f (p'#ps) τs = (let (p,τ) = p' in merges f ps (τs[p := τ \<squnion>f τs!p]))"


lemmas [simp] = Let_def semilat.le_iff_plus_unchanged [symmetric]


lemma (in semilat) nth_merges:
 "!!ss. [|p < length ss; ss ∈ list n A; ∀(p,t)∈set ps. p<n ∧ t∈A |] ==>
  (merges f ps ss)!p = map snd [(p',t') ∈ ps. p'=p] \<Squnion>f ss!p"
  (is "!!ss. [|_; _; ?steptype ps|] ==> ?P ss ps")
(*<*)
proof (induct ps)
  show "!!ss. ?P ss []" by simp

  fix ss p' ps'
  assume ss: "ss ∈ list n A"
  assume l:  "p < length ss"
  assume "?steptype (p'#ps')"
  then obtain a b where
    p': "p'=(a,b)" and ab: "a<n" "b∈A" and "?steptype ps'"
    by (cases p', auto)
  assume "!!ss. p< length ss ==> ss ∈ list n A ==> ?steptype ps' ==> ?P ss ps'"
  hence IH: "!!ss. ss ∈ list n A ==> p < length ss ==> ?P ss ps'" .

  from ss ab
  have "ss[a := b \<squnion>f ss!a] ∈ list n A" by (simp add: closedD)
  moreover
  then have "p < length (ss[a := b \<squnion>f ss!a])" by simp
  ultimately
  have "?P (ss[a := b \<squnion>f ss!a]) ps'" by (rule IH)
  with p' l
  show "?P ss (p'#ps')" by simp
qed
(*>*)


(** merges **)

lemma length_merges [simp]:
  "!!ss. size(merges f ps ss) = size ss"
(*<*) by (induct ps, auto) (*>*)

lemma (in semilat) merges_preserves_type_lemma:
shows "∀xs. xs ∈ list n A --> (∀(p,x) ∈ set ps. p<n ∧ x∈A)
         --> merges f ps xs ∈ list n A"
(*<*)
apply (insert closedI)
apply (unfold closed_def)
apply (induct ps)
 apply simp
apply clarsimp
done
(*>*)

lemma (in semilat) merges_preserves_type [simp]:
 "[| xs ∈ list n A; ∀(p,x) ∈ set ps. p<n ∧ x∈A |]
  ==> merges f ps xs ∈ list n A"
by (simp add: merges_preserves_type_lemma)

lemma (in semilat) merges_incr_lemma:
 "∀xs. xs ∈ list n A --> (∀(p,x)∈set ps. p<size xs ∧ x ∈ A) --> xs [\<sqsubseteq>r] merges f ps xs"
(*<*)
apply (induct ps)
 apply simp
apply simp
apply clarify
apply (rule order_trans)
  apply simp
 apply (erule list_update_incr)
  apply simp
 apply simp
apply (blast intro!: listE_set intro: closedD listE_length [THEN nth_in])
done
(*>*)

lemma (in semilat) merges_incr:
 "[| xs ∈ list n A; ∀(p,x)∈set ps. p<size xs ∧ x ∈ A |] 
  ==> xs [\<sqsubseteq>r] merges f ps xs"
  by (simp add: merges_incr_lemma)


lemma (in semilat) merges_same_conv [rule_format]:
 "(∀xs. xs ∈ list n A --> (∀(p,x)∈set ps. p<size xs ∧ x∈A) --> 
     (merges f ps xs = xs) = (∀(p,x)∈set ps. x \<sqsubseteq>r xs!p))"
(*<*)
  apply (induct_tac ps)
   apply simp
  apply clarsimp
  apply (rename_tac p x ps xs)
  apply (rule iffI)
   apply (rule context_conjI)
    apply (subgoal_tac "xs[p := x \<squnion>f xs!p] [\<sqsubseteq>r] xs")
     apply (force dest!: le_listD simp add: nth_list_update)
    apply (erule subst, rule merges_incr)
       apply (blast intro!: listE_set intro: closedD listE_length [THEN nth_in])
      apply clarify
      apply (rule conjI)
       apply simp
       apply (blast dest: boundedD)
      apply blast
   apply clarify
   apply (erule allE)
   apply (erule impE)
    apply assumption
   apply (drule bspec)
    apply assumption
   apply (simp add: le_iff_plus_unchanged [THEN iffD1] list_update_same_conv [THEN iffD2])
   apply blast
  apply clarify 
  apply (simp add: le_iff_plus_unchanged [THEN iffD1] list_update_same_conv [THEN iffD2])
  done
(*>*)


lemma (in semilat) list_update_le_listI [rule_format]:
  "set xs ⊆ A --> set ys ⊆ A --> xs [\<sqsubseteq>r] ys --> p < size xs -->  
   x \<sqsubseteq>r ys!p --> x∈A --> xs[p := x \<squnion>f xs!p] [\<sqsubseteq>r] ys"
(*<*)
  apply(insert semilat)
  apply (unfold Listn.le_def lesub_def semilat_def)
  apply (simp add: list_all2_conv_all_nth nth_list_update)
  done
(*>*)

lemma (in semilat) merges_pres_le_ub:
shows "[| set ts ⊆ A; set ss ⊆ A;
         ∀(p,t)∈set ps. t \<sqsubseteq>r ts!p ∧ t ∈ A ∧ p < size ts; ss [\<sqsubseteq>r] ts |]
  ==> merges f ps ss [\<sqsubseteq>r] ts"
(*<*)
proof -
  { fix t ts ps
    have
    "!!qs. [|set ts ⊆ A; ∀(p,t)∈set ps. t \<sqsubseteq>r ts!p ∧ t ∈ A ∧ p< size ts |] ==>
    set qs ⊆ set ps  --> 
    (∀ss. set ss ⊆ A --> ss [\<sqsubseteq>r] ts --> merges f qs ss [\<sqsubseteq>r] ts)"
    apply (induct_tac qs)
     apply simp
    apply (simp (no_asm_simp))
    apply clarify
    apply simp
    apply (erule allE, erule impE, erule_tac [2] mp)
     apply (drule bspec, assumption)
     apply (simp add: closedD)
    apply (drule bspec, assumption)
    apply (simp add: list_update_le_listI)
    done 
  } note this [dest]  
  case rule_context
  thus ?thesis by blast
qed
(*>*)


(** propa **)

lemma decomp_propa:
  "!!ss w. (∀(q,t)∈set qs. q < size ss) ==> 
   propa f qs ss w = 
   (merges f qs ss, {q. ∃t.(q,t)∈set qs ∧ t \<squnion>f ss!q ≠ ss!q} ∪ w)"
(*<*)
  apply (induct qs)
   apply simp   
  apply (simp (no_asm))
  apply clarify  
  apply simp
  apply (rule conjI) 
   apply blast
  apply (simp add: nth_list_update)
  apply blast
  done 
(*>*)

(** iter **)

lemma (in semilat) stable_pres_lemma:
shows "[|pres_type step n A; bounded step n; 
     ss ∈ list n A; p ∈ w; ∀q∈w. q < n; 
     ∀q. q < n --> q ∉ w --> stable r step ss q; q < n; 
     ∀s'. (q,s') ∈ set (step p (ss!p)) --> s' \<squnion>f ss!q = ss!q; 
     q ∉ w ∨ q = p |] 
  ==> stable r step (merges f (step p (ss!p)) ss) q"
(*<*)
  apply (unfold stable_def)
  apply (subgoal_tac "∀s'. (q,s') ∈ set (step p (ss!p)) --> s' : A")
   prefer 2
   apply clarify
   apply (erule pres_typeD)
    prefer 3 apply assumption
    apply (rule listE_nth_in)
     apply assumption
    apply simp
   apply simp
  apply simp
  apply clarify
  apply (subst nth_merges)
       apply simp
       apply (blast dest: boundedD)
      apply assumption
     apply clarify
     apply (rule conjI)
      apply (blast dest: boundedD)
     apply (erule pres_typeD)
       prefer 3 apply assumption
      apply simp
     apply simp
apply(subgoal_tac "q < length ss")
prefer 2 apply simp
  apply (frule nth_merges [of q _ _ "step p (ss!p)"]) (* fixme: why does method subst not work?? *)
apply assumption
  apply clarify
  apply (rule conjI)
   apply (blast dest: boundedD)
  apply (erule pres_typeD)
     prefer 3 apply assumption
    apply simp
   apply simp
  apply (drule_tac P = "λx. (a, b) ∈ set (step q x)" in subst)
   apply assumption

 apply (simp add: plusplus_empty)
 apply (cases "q ∈ w")
  apply simp
  apply (rule ub1')
     apply assumption
    apply clarify
    apply (rule pres_typeD)
       apply assumption
      prefer 3 apply assumption
     apply (blast intro: listE_nth_in dest: boundedD)
    apply (blast intro: pres_typeD dest: boundedD)
   apply (blast intro: listE_nth_in dest: boundedD)
  apply assumption

 apply simp
 apply (erule allE, erule impE, assumption, erule impE, assumption)
 apply (rule order_trans)
   apply simp
  defer
 apply (rule pp_ub2)(*
    apply assumption*)
   apply simp
   apply clarify
   apply simp
   apply (rule pres_typeD)
      apply assumption
     prefer 3 apply assumption
    apply (blast intro: listE_nth_in dest: boundedD)
   apply (blast intro: pres_typeD dest: boundedD)
  apply (blast intro: listE_nth_in dest: boundedD)
 apply blast
 done
(*>*)


lemma (in semilat) merges_bounded_lemma:
 "[| mono r step n A; bounded step n; 
    ∀(p',s') ∈ set (step p (ss!p)). s' ∈ A; ss ∈ list n A; ts ∈ list n A; p < n; 
    ss [\<sqsubseteq>r] ts; ∀p. p < n --> stable r step ts p |] 
  ==> merges f (step p (ss!p)) ss [\<sqsubseteq>r] ts" 
(*<*)
  apply (unfold stable_def)
  apply (rule merges_pres_le_ub)
     apply simp
    apply simp
   prefer 2 apply assumption

  apply clarsimp
  apply (drule boundedD, assumption+)
  apply (erule allE, erule impE, assumption)
  apply (drule bspec, assumption)
  apply simp

  apply (drule monoD [of _ _ _ _ p "ss!p"  "ts!p"])
     apply assumption
    apply simp
   apply (simp add: le_listD)
  
  apply (drule lesub_step_typeD, assumption) 
  apply clarify
  apply (drule bspec, assumption)
  apply simp
  apply (blast intro: order_trans)
  done
(*>*)

lemma termination_lemma: includes semilat
shows "[| ss ∈ list n A; ∀(q,t)∈set qs. q<n ∧ t∈A; p∈w |] ==> 
      ss [\<sqsubset>r] merges f qs ss ∨ 
  merges f qs ss = ss ∧ {q. ∃t. (q,t)∈set qs ∧ t \<squnion>f ss!q ≠ ss!q} ∪ (w-{p}) ⊂ w"
(*<*)
apply(insert semilat)
  apply (unfold lesssub_def)
  apply (simp (no_asm_simp) add: merges_incr)
  apply (rule impI)
  apply (rule merges_same_conv [THEN iffD1, elim_format]) 
  apply assumption+
    defer
    apply (rule sym, assumption)
   defer apply simp
   apply (subgoal_tac "∀q t. ¬((q, t) ∈ set qs ∧ t \<squnion>f ss ! q ≠ ss ! q)")
   apply (blast intro!: psubsetI elim: equalityE)
   apply clarsimp
   apply (drule bspec, assumption) 
   apply (drule bspec, assumption)
   apply clarsimp
  done 
(*>*)

lemma iter_properties[rule_format]: includes semilat
shows "[| acc r; pres_type step n A; mono r step n A;
     bounded step n; ∀p∈w0. p < n; ss0 ∈ list n A;
     ∀p<n. p ∉ w0 --> stable r step ss0 p |] ==>
   iter f step ss0 w0 = (ss',w')
   -->
   ss' ∈ list n A ∧ stables r step ss' ∧ ss0 [\<sqsubseteq>r] ss' ∧
   (∀ts∈list n A. ss0 [\<sqsubseteq>r] ts ∧ stables r step ts --> ss' [\<sqsubseteq>r] ts)"
(*<*)
apply(insert semilat)
apply (unfold iter_def stables_def)
apply (rule_tac P = "λ(ss,w).
 ss ∈ list n A ∧ (∀p<n. p ∉ w --> stable r step ss p) ∧ ss0 [\<sqsubseteq>r] ss ∧
 (∀ts∈list n A. ss0 [\<sqsubseteq>r] ts ∧ stables r step ts --> ss [\<sqsubseteq>r] ts) ∧
 (∀p∈w. p < n)" and
 r = "{(ss',ss) . ss [\<sqsubset>r] ss'} <*lex*> finite_psubset"
       in while_rule)

-- "Invariant holds initially:"
apply (simp add:stables_def)

-- "Invariant is preserved:"
apply(simp add: stables_def split_paired_all)
apply(rename_tac ss w)
apply(subgoal_tac "(SOME p. p ∈ w) ∈ w")
 prefer 2; apply (fast intro: someI)
apply(subgoal_tac "∀(q,t) ∈ set (step (SOME p. p ∈ w) (ss ! (SOME p. p ∈ w))). q < length ss ∧ t ∈ A")
 prefer 2
 apply clarify
 apply (rule conjI)
  apply(clarsimp, blast dest!: boundedD)
 apply (erule pres_typeD)
  prefer 3
  apply assumption
  apply (erule listE_nth_in)
  apply blast
 apply blast
apply (subst decomp_propa)
 apply blast
apply simp
apply (rule conjI)
 apply (rule merges_preserves_type)
 apply blast
 apply clarify
 apply (rule conjI)
  apply(clarsimp, blast dest!: boundedD)
 apply (erule pres_typeD)
  prefer 3
  apply assumption
  apply (erule listE_nth_in)
  apply blast
 apply blast
apply (rule conjI)
 apply clarify
 apply (blast intro!: stable_pres_lemma)
apply (rule conjI)
 apply (blast intro!: merges_incr intro: le_list_trans)
apply (rule conjI)
 apply clarsimp
 apply (blast intro!: merges_bounded_lemma)
apply (blast dest!: boundedD)


-- "Postcondition holds upon termination:"
apply(clarsimp simp add: stables_def split_paired_all)

-- "Well-foundedness of the termination relation:"
apply (rule wf_lex_prod)
 apply (insert orderI [THEN acc_le_listI])
 apply (simp only: acc_def lesssub_def)
apply (rule wf_finite_psubset) 

-- "Loop decreases along termination relation:"
apply(simp add: stables_def split_paired_all)
apply(rename_tac ss w)
apply(subgoal_tac "(SOME p. p ∈ w) ∈ w")
 prefer 2; apply (fast intro: someI)
apply(subgoal_tac "∀(q,t) ∈ set (step (SOME p. p ∈ w) (ss ! (SOME p. p ∈ w))). q < length ss ∧ t ∈ A")
 prefer 2
 apply clarify
 apply (rule conjI)
  apply(clarsimp, blast dest!: boundedD)
 apply (erule pres_typeD)
  prefer 3
  apply assumption
  apply (erule listE_nth_in)
  apply blast
 apply blast
apply (subst decomp_propa)
 apply blast
apply clarify
apply (simp del: listE_length
    add: lex_prod_def finite_psubset_def 
         bounded_nat_set_is_finite)
apply (rule termination_lemma)
apply assumption+
defer
apply assumption
apply clarsimp
done
(*>*)


lemma kildall_properties: includes semilat
shows "[| acc r; pres_type step n A; mono r step n A;
     bounded step n; ss0 ∈ list n A |] ==>
  kildall r f step ss0 ∈ list n A ∧
  stables r step (kildall r f step ss0) ∧
  ss0 [\<sqsubseteq>r] kildall r f step ss0 ∧
  (∀ts∈list n A. ss0 [\<sqsubseteq>r] ts ∧ stables r step ts -->
                 kildall r f step ss0 [\<sqsubseteq>r] ts)"
(*<*)
apply (unfold kildall_def)
apply(case_tac "iter f step ss0 (unstables r step ss0)")
apply(simp)
apply (rule iter_properties)
by (simp_all add: unstables_def stable_def)


lemma is_bcv_kildall: includes semilat
shows "[| acc r; top r T; pres_type step n A; bounded step n; mono r step n A |]
  ==> is_bcv r T step n A (kildall r f step)"
apply(unfold is_bcv_def wt_step_def)
apply(insert semilat kildall_properties[of A])
apply(simp add:stables_def)
apply clarify
apply(subgoal_tac "kildall r f step τs0 ∈ list n A")
 prefer 2 apply (simp(no_asm_simp))
apply (rule iffI)
 apply (rule_tac x = "kildall r f step τs0" in bexI) 
  apply (rule conjI)
   apply (blast)
  apply (simp  (no_asm_simp))
 apply(assumption)
apply clarify
apply(subgoal_tac "kildall r f step τs0!p <=_r τs!p")
 apply simp
apply (blast intro!: le_listD less_lengthI)
done
(*>*)

end