Definition dummy {X Y} (P : X -> Prop) (Q : Y -> Prop) : X -> Y -> Prop :=
fun x y => P x /\ Q y.

Theorem read_commute : forall k1 k2,
poram_equiv
eq
(v1 <- read k1;; v2 <- read k2;; mreturn (v1, v2))
(v2 <- read k2;; v1 <- read k1;; mreturn (v1, v2)).