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(** Testing the performance of [pattern]. For not regressing on COQBUG(https://github.com/coq/coq/issues/11150) and COQBUG(https://github.com/coq/coq/issues/6502) *)
(* Expected time < 2.00s *)
(* reference: 0.673s after adjustment *)
Definition Let_In {A P} (v : A) (f : forall x : A, P x) : P v
:= let x := v in f x.
Fixpoint big (a : nat) (sz : nat) : nat
:= match sz with
| O => a
| S sz' => Let_In (a * a) (fun a' => big a' sz')
end.
Ltac do_time n :=
try (
once (assert (exists e, e = big 1 n);
[ lazy -[big]; (*match goal with |- ?G => idtac G end;*) lazy [big];
time pattern Nat.mul, S, O, (@Let_In nat (fun _ => nat))
| ]);
fail).
Ltac do_time_to n :=
lazymatch (eval vm_compute in n) with
| O => idtac
| ?n' => do_time_to (Nat.div2 n'); idtac n'; do_time n'
end.
Local Set Warnings "-abstract-large-number".
(* Don't spend lots of time printing *)
Notation hide := (_ = _).
Goal True.
Proof.
(* do_time_to 16384. *) (* should be linear, not quadratic *)
assert (exists e, e = big 1 16384).
lazy -[big]; (*match goal with |- ?G => idtac G end;*) lazy [big].
Timeout 15 Time pattern Nat.mul, S, O, (@Let_In nat (fun _ => nat)).
Abort.
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