frap/SharedMemory.v

93 lines
3.4 KiB
Coq
Raw Normal View History

(** Formal Reasoning About Programs <http://adam.chlipala.net/frap/>
* Chapter 13: Operational Semantics for Shared-Memory Concurrency
* Author: Adam Chlipala
* License: https://creativecommons.org/licenses/by-nc-nd/4.0/ *)
Require Import Frap.
Set Implicit Arguments.
Set Asymmetric Patterns.
(** * Shared notations and definitions; main material starts afterward. *)
Notation "m $! k" := (match m $? k with Some n => n | None => O end) (at level 30).
Definition heap := fmap nat nat.
Definition assertion := heap -> Prop.
Hint Extern 1 (_ <= _) => linear_arithmetic.
Hint Extern 1 (@eq nat _ _) => linear_arithmetic.
Ltac simp := repeat (simplify; subst; propositional;
try match goal with
| [ H : ex _ |- _ ] => invert H
end); try linear_arithmetic.
(** * An object language with shared-memory concurrency *)
Inductive loop_outcome acc :=
| Done (a : acc)
| Again (a : acc).
Inductive cmd : Set -> Type :=
| Return {result : Set} (r : result) : cmd result
| Bind {result result'} (c1 : cmd result') (c2 : result' -> cmd result) : cmd result
| Read (a : nat) : cmd nat
| Write (a v : nat) : cmd unit
| Loop {acc : Set} (init : acc) (body : acc -> cmd (loop_outcome acc)) : cmd acc
| Fail {result} : cmd result
(* Now here's the new part: parallel composition of commands. *)
| Par (c1 c2 : cmd unit) : cmd unit
(* Let's also add locking commands, where locks are named by [nat]s. *)
| Lock (a : nat) : cmd unit
| Unlock (a : nat) : cmd unit.
Notation "x <- c1 ; c2" := (Bind c1 (fun x => c2)) (right associativity, at level 80).
Notation "'for' x := i 'loop' c1 'done'" := (Loop i (fun x => c1)) (right associativity, at level 80).
Infix "||" := Par.
Definition locks := set nat.
Inductive step : forall A, heap * locks * cmd A -> heap * locks * cmd A -> Prop :=
| StepBindRecur : forall result result' (c1 c1' : cmd result') (c2 : result' -> cmd result) h h' l l',
step (h, l, c1) (h', l', c1')
-> step (h, l, Bind c1 c2) (h', l', Bind c1' c2)
| StepBindProceed : forall (result result' : Set) (v : result') (c2 : result' -> cmd result) h l,
step (h, l, Bind (Return v) c2) (h, l, c2 v)
| StepLoop : forall (acc : Set) (init : acc) (body : acc -> cmd (loop_outcome acc)) h l,
step (h, l, Loop init body) (h, l, o <- body init; match o with
| Done a => Return a
| Again a => Loop a body
end)
| StepRead : forall h l a,
step (h, l, Read a) (h, l, Return (h $! a))
| StepWrite : forall h l a v,
step (h, l, Write a v) (h $+ (a, v), l, Return tt)
| StepParRecur1 : forall h l c1 c2 h' l' c1',
step (h, l, c1) (h', l', c1')
-> step (h, l, Par c1 c2) (h', l', Par c1' c2)
| StepParRecur2 : forall h l c1 c2 h' l' c2',
step (h, l, c2) (h', l', c2')
-> step (h, l, Par c1 c2) (h', l', Par c1 c2')
| StepParProceed1 : forall h l c2,
step (h, l, Par (Return tt) c2) (h, l, c2)
| StepParProceed2 : forall h l c1,
step (h, l, Par c1 (Return tt)) (h, l, c1)
| StepLock : forall h l a,
~a \in l
-> step (h, l, Lock a) (h, l \cup {a}, Return tt)
| StepUnlock : forall h l a,
a \in l
-> step (h, l, Unlock a) (h, l \setminus {a}, Return tt).
Definition trsys_of (h : heap) (l : locks) {result} (c : cmd result) := {|
Initial := {(h, l, c)};
Step := step (A := result)
|}.