Library iris.algebra.sts

From iris.prelude Require Export set.
From iris.algebra Require Export cmra.
From iris.algebra Require Import dra.
Local Arguments valid _ _ !_ /.
Local Arguments op _ _ !_ !_ /.
Local Arguments core _ _ !_ /.

Definition of STSs

Module sts.
Structure stsT := STS {
  state : Type;
  token : Type;
  prim_step : relation state;
  tok : state set token;
}.
Arguments STS {_ _} _ _.
Arguments prim_step {_} _ _.
Arguments tok {_} _.
Notation states sts := (set (state sts)).
Notation tokens sts := (set (token sts)).

Theory and definitions

Section sts.
Context {sts : stsT}.

Step relations

Inductive step : relation (state sts × tokens sts) :=
  | Step s1 s2 T1 T2 :
     prim_step s1 s2 tok s1 T1 tok s2 T2
     tok s1 T1 tok s2 T2 step (s1,T1) (s2,T2).
Notation steps := (rtc step).
Inductive frame_step (T : tokens sts) (s1 s2 : state sts) : Prop :=
  | Frame_step T1 T2 :
     T1 tok s1 T step (s1,T1) (s2,T2) frame_step T s1 s2.

Closure under frame steps

Record closed (S : states sts) (T : tokens sts) : Prop := Closed {
  closed_disjoint s : s S tok s T;
  closed_step s1 s2 : s1 S frame_step T s1 s2 s2 S
}.
Definition up (s : state sts) (T : tokens sts) : states sts :=
  {[ s' | rtc (frame_step T) s s' ]}.
Definition up_set (S : states sts) (T : tokens sts) : states sts :=
  S ≫= λ s, up s T.

Tactic setup
Hint Resolve Step.
Hint Extern 50 (equiv (A:=set _) _ _) ⇒ set_solver : sts.
Hint Extern 50 (¬equiv (A:=set _) _ _) ⇒ set_solver : sts.
Hint Extern 50 (_ _) ⇒ set_solver : sts.
Hint Extern 50 (_ _) ⇒ set_solver : sts.
Hint Extern 50 (_ _) ⇒ set_solver : sts.

Setoids

Instance framestep_mono : Proper (flip (⊆) ==> (=) ==> (=) ==> impl) frame_step.
Proof.
  intros ?? HT ?? <- ?? <-; destruct 1; econstructor;
    eauto with sts; set_solver.
Qed.
Global Instance framestep_proper : Proper ((≡) ==> (=) ==> (=) ==> iff) frame_step.
Proof. move⇒ ?? /collection_equiv_spec [??]; split; by apply framestep_mono. Qed.
Instance closed_proper' : Proper ((≡) ==> (≡) ==> impl) closed.
Proof. destruct 3; constructor; intros until 0; setoid_subst; eauto. Qed.
Global Instance closed_proper : Proper ((≡) ==> (≡) ==> iff) closed.
Proof. by split; apply closed_proper'. Qed.
Global Instance up_preserving : Proper ((=) ==> flip (⊆) ==> (⊆)) up.
Proof.
  intros s ? <- T T' HT ; apply elem_of_subseteq.
  induction 1 as [|s1 s2 s3 [T1 T2]]; [constructor|].
  eapply elem_of_mkSet, rtc_l; [eapply Frame_step with T1 T2|]; eauto with sts.
Qed.
Global Instance up_proper : Proper ((=) ==> (≡) ==> (≡)) up.
Proof.
  by move⇒ ??? ?? /collection_equiv_spec [??]; split; apply up_preserving.
Qed.
Global Instance up_set_preserving : Proper ((⊆) ==> flip (⊆) ==> (⊆)) up_set.
Proof.
  intros S1 S2 HS T1 T2 HT. rewrite /up_set.
  f_equiv; last done. moves1 s2 Hs. simpl in HT. by apply up_preserving.
Qed.
Global Instance up_set_proper : Proper ((≡) ==> (≡) ==> (≡)) up_set.
Proof.
  moveS1 S2 /collection_equiv_spec [??] T1 T2 /collection_equiv_spec [??];
    split; by apply up_set_preserving.
Qed.

Properties of closure under frame steps

Lemma closed_steps S T s1 s2 :
  closed S T s1 S rtc (frame_step T) s1 s2 s2 S.
Proof. induction 3; eauto using closed_step. Qed.
Lemma closed_op T1 T2 S1 S2 :
  closed S1 T1 closed S2 T2 closed (S1 S2) (T1 T2).
Proof.
  intros [? Hstep1] [? Hstep2]; split; [set_solver|].
  intros s3 s4; rewrite !elem_of_intersection; intros [??] [T3 T4 ?]; split.
  - apply Hstep1 with s3, Frame_step with T3 T4; auto with sts.
  - apply Hstep2 with s3, Frame_step with T3 T4; auto with sts.
Qed.
Lemma step_closed s1 s2 T1 T2 S Tf :
  step (s1,T1) (s2,T2) closed S Tf s1 S T1 Tf
  s2 S T2 Tf tok s2 T2.
Proof.
  inversion_clear 1 as [???? HR Hs1 Hs2]; intros [? Hstep]??; split_and?; auto.
  - eapply Hstep with s1, Frame_step with T1 T2; auto with sts.
  - set_solver -Hstep Hs1 Hs2.
Qed.
Lemma steps_closed s1 s2 T1 T2 S Tf :
  steps (s1,T1) (s2,T2) closed S Tf s1 S T1 Tf
  tok s1 T1 s2 S T2 Tf tok s2 T2.
Proof.
  remember (s1,T1) as sT1 eqn:HsT1; remember (s2,T2) as sT2 eqn:HsT2.
  intros Hsteps; revert s1 T1 HsT1 s2 T2 HsT2.
  induction Hsteps as [?|? [s2 T2] ? Hstep Hsteps IH];
     intros s1 T1 HsT1 s2' T2' ?????; simplify_eq; first done.
  destruct (step_closed s1 s2 T1 T2 S Tf) as (?&?&?); eauto.
Qed.

Properties of the closure operators

Lemma elem_of_up s T : s up s T.
Proof. constructor. Qed.
Lemma subseteq_up_set S T : S up_set S T.
Proof. intros s ?; apply elem_of_bind; eauto using elem_of_up. Qed.
Lemma up_up_set s T : up s T up_set {[ s ]} T.
Proof. by rewrite /up_set collection_bind_singleton. Qed.
Lemma closed_up_set S T : ( s, s S tok s T) closed (up_set S T) T.
Proof.
  intros HS; unfold up_set; split.
  - intros s; rewrite !elem_of_bind; intros (s'&Hstep&Hs').
    specialize (HS s' Hs'); clear Hs' S.
    induction Hstep as [s|s1 s2 s3 [T1 T2 ? Hstep] ? IH]; first done.
    inversion_clear Hstep; apply IH; clear IH; auto with sts.
  - intros s1 s2; rewrite /up; set_unfold; intros (s&?&?) ?; s.
    split; [eapply rtc_r|]; eauto.
Qed.
Lemma closed_up s T : tok s T closed (up s T) T.
Proof.
  intros; rewrite -(collection_bind_singleton (λ s, up s T) s).
  apply closed_up_set; set_solver.
Qed.
Lemma closed_up_set_empty S : closed (up_set S ) .
Proof. eauto using closed_up_set with sts. Qed.
Lemma closed_up_empty s : closed (up s ) .
Proof. eauto using closed_up with sts. Qed.
Lemma up_set_empty S T : up_set S T S .
Proof. move:(subseteq_up_set S T). set_solver. Qed.
Lemma up_set_non_empty S T : S up_set S T .
Proof. by move=>? /up_set_empty. Qed.
Lemma up_non_empty s T : up s T .
Proof. eapply non_empty_inhabited, elem_of_up. Qed.
Lemma up_closed S T : closed S T up_set S T S.
Proof.
  intros ?; apply collection_equiv_spec; split; auto using subseteq_up_set.
  intros s; unfold up_set; rewrite elem_of_bind; intros (s'&Hstep&?).
  induction Hstep; eauto using closed_step.
Qed.
Lemma up_subseteq s T S : closed S T s S sts.up s T S.
Proof. move⇒ ?? s' ?. eauto using closed_steps. Qed.
Lemma up_set_subseteq S1 T S2 : closed S2 T S1 S2 sts.up_set S1 T S2.
Proof. move⇒ ?? s [s' [? ?]]. eauto using closed_steps. Qed.
End sts.

Notation steps := (rtc step).

Inductive car (sts : stsT) :=
  | auth : state sts set (token sts) car sts
  | frag : set (state sts) set (token sts ) car sts.
Arguments auth {_} _ _.
Arguments frag {_} _ _.
End sts.

Notation stsT := sts.stsT.
Notation STS := sts.STS.

STSs form a disjoint RA

Section sts_dra.
Context (sts : stsT).
Import sts.
Implicit Types S : states sts.
Implicit Types T : tokens sts.

Inductive sts_equiv : Equiv (car sts) :=
  | auth_equiv s T1 T2 : T1 T2 auth s T1 auth s T2
  | frag_equiv S1 S2 T1 T2 : T1 T2 S1 S2 frag S1 T1 frag S2 T2.
Existing Instance sts_equiv.
Instance sts_valid : Valid (car sts) := λ x,
  match x with
  | auth s Ttok s T
  | frag S' Tclosed S' T S'
  end.
Instance sts_core : Core (car sts) := λ x,
  match x with
  | frag S' _frag (up_set S' )
  | auth s _frag (up s )
  end.
Inductive sts_disjoint : Disjoint (car sts) :=
  | frag_frag_disjoint S1 S2 T1 T2 :
     S1 S2 T1 T2 frag S1 T1 frag S2 T2
  | auth_frag_disjoint s S T1 T2 : s S T1 T2 auth s T1 frag S T2
  | frag_auth_disjoint s S T1 T2 : s S T1 T2 frag S T1 auth s T2.
Existing Instance sts_disjoint.
Instance sts_op : Op (car sts) := λ x1 x2,
  match x1, x2 with
  | frag S1 T1, frag S2 T2frag (S1 S2) (T1 T2)
  | auth s T1, frag _ T2auth s (T1 T2)
  | frag _ T1, auth s T2auth s (T1 T2)
  | auth s T1, auth _ T2auth s (T1 T2)
  end.
Global Instance sts_step : step.Step (car sts) := λ x1 x2,
  s1 T1 y1 s2 T2 y2, (auth s1 T1 y1) (x1 auth s1 T1 y1)
                            (auth s2 T2 y2) (x2 auth s2 T2 y2)
                            (tc prim_step) s1 s2.

Hint Extern 50 (equiv (A:=set _) _ _) ⇒ set_solver : sts.
Hint Extern 50 (¬equiv (A:=set _) _ _) ⇒ set_solver : sts.
Hint Extern 50 (_ _) ⇒ set_solver : sts.
Hint Extern 50 (_ _) ⇒ set_solver : sts.
Hint Extern 50 (_ _) ⇒ set_solver : sts.

Global Instance auth_proper s : Proper ((≡) ==> (≡)) (@auth sts s).
Proof. by constructor. Qed.
Global Instance frag_proper : Proper ((≡) ==> (≡) ==> (≡)) (@frag sts).
Proof. by constructor. Qed.

Instance sts_equivalence: Equivalence ((≡) : relation (car sts)).
Proof.
  split.
  - by intros []; constructor.
  - by destruct 1; constructor.
  - destruct 1; inversion_clear 1; constructor; etrans; eauto.
Qed.
Lemma auth_disj_decomp x s1 T1 f1 s2 T2 f2:
  auth s1 T1 f1 x auth s1 T1 f1 auth s2 T2 f2 x auth s2 T2 f2
  s1 = s2.
Proof.
  intros Hdisj1 Heq1 Hdisj2 Heq2.
  inversion Hdisj1 as [| ? ? ? Sf1 |]; subst.
  inversion Hdisj2 as [| ? ? ? Sf2 |]; subst.
  rewrite /op /sts_op in Heq1 Heq2.
  rewrite Heq1 in Heq2 *; intro Heq_auth.
  inversion Heq_auth; auto.
Qed.

Lemma sts_step_trans: Transitive (sts_step).
Proof.
  intros x y z (s1 & T1 & a1 & s2 & T2 & a2 & Hdisj1 & Heqx & Hdisj2 & Heqy & Htc)
               (s1' & T1' & a1' & s2' & T2' & a2' & Hdisj1' & Heqy' & Hdisj2' & Heqz & Htc').
   s1, T1, a1, s2', T2', a2'.
  split_and?; eauto.
  assert (s2 = s1') by eauto using auth_disj_decomp.
  subst. eauto with ars.
Qed.

Instance sts_step_proper: Proper (equiv ==> equiv ==> impl) sts_step.
Proof.
  intros x y Heq x' y' Heq' Hstep.
  rewrite /step /sts_step in Hstep ×.
  destruct Hstep as (s1 & T1 & y1 & s2 & T2 & y2 & Hdisj & Heqx & Hdisj' & Heqx' & Htc).
   s1, T1, y1, s2, T2, y2.
  split_and?; rewrite -?Heq -?Heq'; eauto.
Qed.

Lemma sts_dra_mixin : DRAMixin (car sts).
Proof.
  split.
  - apply _.
  - by do 2 destruct 1; constructor; setoid_subst.
  - by destruct 1; constructor; setoid_subst.
  - by destruct 1; simpl; intros ?; setoid_subst.
  - by intros ? [|]; destruct 1; inversion_clear 1; constructor; setoid_subst.
  - exact sts_step_proper.
  - destruct 3; simpl in *; destruct_and?; eauto using closed_op;
      match goal with H : closed _ _ |- _destruct H end; set_solver.
  - intros []; simpl; intros; destruct_conjs; split;
      eauto using closed_up, up_non_empty, closed_up_set, up_set_empty with sts.
  - intros [] [] []; constructor; rewrite ?assoc; auto with sts.
  - destruct 4; inversion_clear 1; constructor; auto with sts.
  - destruct 4; inversion_clear 1; constructor; auto with sts.
  - destruct 1; constructor; auto with sts.
  - destruct 3; constructor; auto with sts.
  - intros [|S T]; constructor; auto using elem_of_up with sts.
  - intros [|S T]; constructor; auto with sts.
  - intros [s T|S T]; constructor; auto with sts.
    + rewrite (up_closed (up _ _)); auto using closed_up with sts.
    + rewrite (up_closed (up_set _ _)); eauto using closed_up_set with sts.
  - intros x y. (core (x y))=> ?? Hxy; split_and?.
    + destruct Hxy; constructor; unfold up_set; set_solver.
    + destruct Hxy; simpl; split_and?;
        auto using closed_up_set_empty, closed_up_empty, up_non_empty; [].
      apply up_set_non_empty. set_solver.
    + destruct Hxy; constructor;
        repeat match goal with
        | |- context [ up_set ?S ?T ] ⇒
           unless (S up_set S T) by done; pose proof (subseteq_up_set S T)
        | |- context [ up ?s ?T ] ⇒
           unless (s up s T) by done; pose proof (elem_of_up s T)
        end; auto with sts.
  - intros [| S T] [| S' T']; simpl.
    + intros. econstructor; first set_solver+.
      apply up_closed.
      assert ((: tokens sts) ) asby rewrite ?right_id //=;
      apply closed_op; rewrite ?right_id; apply closed_up; set_solver.
    + intros. econstructor; first set_solver+.
      apply up_closed.
      assert ((: tokens sts) ) asby rewrite ?right_id //=.
      apply closed_op; rewrite ?right_id.
      × apply closed_up; set_solver.
      × apply closed_up_set; set_solver.
    + intros. econstructor; first set_solver+.
      apply up_closed.
      assert ((: tokens sts) ) asby rewrite ?right_id //=.
      apply closed_op; rewrite ?right_id.
      × apply closed_up_set; set_solver.
      × apply closed_up; set_solver.
    + intros. econstructor; first set_solver+.
      apply up_closed.
      assert ((: tokens sts) ) asby rewrite ?right_id //=.
      apply closed_op; rewrite ?right_id.
      × apply closed_up_set; set_solver.
      × apply closed_up_set; set_solver.
Qed.
Canonical Structure stsDR : draT := DRAT (car sts) sts_dra_mixin.
End sts_dra.

The STS Resource Algebra

Finally, the general theory of STS that should be used by users
Notation stsC sts := (validityC (stsDR sts)).
Notation stsR sts := (validityR (stsDR sts)).

Section sts_definitions.
  Context {sts : stsT}.
  Definition sts_auth (s : sts.state sts) (T : sts.tokens sts) : stsR sts :=
    to_validity (sts.auth s T).
  Definition sts_frag (S : sts.states sts) (T : sts.tokens sts) : stsR sts :=
    to_validity (sts.frag S T).
  Definition sts_frag_up (s : sts.state sts) (T : sts.tokens sts) : stsR sts :=
    sts_frag (sts.up s T) T.
End sts_definitions.
Instance: Params (@sts_auth) 2.
Instance: Params (@sts_frag) 1.
Instance: Params (@sts_frag_up) 2.

Section stsRA.
Import sts.
Context {sts : stsT}.
Implicit Types s : state sts.
Implicit Types S : states sts.
Implicit Types T : tokens sts.
Arguments dra_valid _ !_/.

Setoids
Global Instance sts_auth_proper s : Proper ((≡) ==> (≡)) (sts_auth s).
Proof. solve_proper. Qed.
Global Instance sts_frag_proper : Proper ((≡) ==> (≡) ==> (≡)) (@sts_frag sts).
Proof. solve_proper. Qed.
Global Instance sts_frag_up_proper s : Proper ((≡) ==> (≡)) (sts_frag_up s).
Proof. solve_proper. Qed.

Validity
Lemma sts_auth_valid s T : sts_auth s T tok s T.
Proof. done. Qed.
Lemma sts_frag_valid S T : sts_frag S T closed S T S .
Proof. done. Qed.
Lemma sts_frag_up_valid s T : tok s T sts_frag_up s T.
Proof. intros. by apply sts_frag_valid; auto using closed_up, up_non_empty. Qed.

Lemma sts_auth_frag_valid_inv s S T1 T2 :
   (sts_auth s T1 sts_frag S T2) s S.
Proof. by intros (?&?&Hdisj); inversion Hdisj. Qed.

Op
Lemma sts_op_auth_frag s S T :
  s S closed S T sts_auth s sts_frag S T sts_auth s T.
Proof.
  intros; split; [split|constructor; set_solver]; simpl.
  - intros (?&?&?); by apply closed_disjoint with S.
  - intros; split_and?; last constructor; set_solver.
Qed.
Lemma sts_op_auth_frag_up s T :
  sts_auth s sts_frag_up s T sts_auth s T.
Proof.
  intros; split; [split|constructor; set_solver]; simpl.
  - intros (?&[??]&?). by apply closed_disjoint with (up s T), elem_of_up.
  - intros; split_and?.
    + set_solver+.
    + by apply closed_up.
    + apply up_non_empty.
    + constructor; last set_solver. apply elem_of_up.
Qed.

Lemma sts_op_frag S1 S2 T1 T2 :
  T1 T2 sts.closed S1 T1 sts.closed S2 T2
  sts_frag (S1 S2) (T1 T2) sts_frag S1 T1 sts_frag S2 T2.
Proof.
  intros HT HS1 HS2. rewrite /sts_frag -to_validity_op //.
  move=>/=[??]. split_and!; [auto; set_solver..|by constructor].
Qed.

Frame preserving updates
Lemma sts_update_auth s1 s2 T1 T2 :
  steps (s1,T1) (s2,T2) sts_auth s1 T1 ~~> sts_auth s2 T2.
Proof.
  intros ?; apply validity_update.
  inversion 3 as [|? S ? Tf|]; simplify_eq/=; destruct_and?.
  destruct (steps_closed s1 s2 T1 T2 S Tf) as (?&?&?); auto; [].
  repeat (done || constructor).
Qed.

Lemma sts_update_frag S1 S2 T1 T2 :
  closed S2 T2 S1 S2 T2 T1 sts_frag S1 T1 ~~> sts_frag S2 T2.
Proof.
  rewrite /sts_frag⇒ ? HS HT. apply validity_update.
  inversion 3 as [|? S ? Tf|]; simplify_eq/=.
  - split_and!; first done; first set_solver. constructor; set_solver.
  - split_and!; first done; first set_solver. constructor; set_solver.
Qed.

Lemma sts_update_frag_up s1 S2 T1 T2 :
  closed S2 T2 s1 S2 T2 T1 sts_frag_up s1 T1 ~~> sts_frag S2 T2.
Proof.
  intros ? ? HT; apply sts_update_frag; [intros; eauto using closed_steps..].
  rewrite <-HT. eapply up_subseteq; done.
Qed.

Lemma sts_up_set_intersection S1 Sf Tf :
  closed Sf Tf S1 Sf S1 up_set (S1 Sf) Tf.
Proof.
  intros Hclf. apply (anti_symm (⊆)).
  - moves [HS1 HSf]. split. by apply HS1. by apply subseteq_up_set.
  - moves [HS1 [s' [/elem_of_mkSet Hsup Hs']]]. split; first done.
    eapply closed_steps, Hsup; first done. set_solver +Hs'.
Qed.

Inclusion
End stsRA.

STSs without tokens: Some stuff is simpler
Module sts_notok.
Structure stsT := STS {
  state : Type;
  prim_step : relation state;
}.
Arguments STS {_} _.
Arguments prim_step {_} _ _.
Notation states sts := (set (state sts)).

Canonical sts_notok (sts : stsT) : sts.stsT :=
  sts.STS (token:=Empty_set) (@prim_step sts) (λ _, ).

Section sts.
Context {sts : stsT}.
Implicit Types s : state sts.
Implicit Types S : states sts.

Notation prim_steps := (rtc prim_step).

Lemma sts_step s1 s2 :
  prim_step s1 s2 sts.step (s1, ) (s2, ).
Proof.
  intros. split; set_solver.
Qed.

Lemma sts_steps s1 s2 :
  prim_steps s1 s2 sts.steps (s1, ) (s2, ).
Proof.
  induction 1; eauto using sts_step, rtc_refl, rtc_l.
Qed.

Lemma frame_prim_step T s1 s2 :
  sts.frame_step T s1 s2 prim_step s1 s2.
Proof.
  inversion 1 as [??? Hstep]. inversion_clear Hstep. done.
Qed.

Lemma prim_frame_step T s1 s2 :
  prim_step s1 s2 sts.frame_step T s1 s2.
Proof.
  intros Hstep. apply sts.Frame_step with ; first set_solver.
  by apply sts_step.
Qed.

Lemma mk_closed S :
  ( s1 s2, s1 S prim_step s1 s2 s2 S) sts.closed S .
Proof.
  intros ?. constructor; first by set_solver.
  intros ????. eauto using frame_prim_step.
Qed.

End sts.
Notation steps := (rtc prim_step).
End sts_notok.

Coercion sts_notok.sts_notok : sts_notok.stsT >-> sts.stsT.
Notation sts_notokT := sts_notok.stsT.
Notation STS_NoTok := sts_notok.STS.

Section sts_notokRA.
Import sts_notok.
Context {sts : sts_notokT}.
Implicit Types s : state sts.
Implicit Types S : states sts.

Lemma sts_notok_update_auth s1 s2 :
  rtc prim_step s1 s2 sts_auth s1 ~~> sts_auth s2 .
Proof.
  intros. by apply sts_update_auth, sts_steps.
Qed.

End sts_notokRA.