From 6c73afbe5b948b37e093996037cd203b32a85c23 Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Mon, 10 Jul 2023 11:00:34 -0400
Subject: [PATCH] perf: optimize `Fut.for_` a bit

remove intermediate array.
---
 src/fut.ml | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/fut.ml b/src/fut.ml
index e998ae32..821a77f0 100644
--- a/src/fut.ml
+++ b/src/fut.ml
@@ -308,10 +308,12 @@ let wait_list (a : _ t list) : unit t =
   join_container_ a ~iter:List.iter ~len:List.length ~map:(fun _f _ -> ())
 
 let for_ ~on n f : unit t =
-  let futs = Array.init n (fun i -> spawn ~on (fun () -> f i)) in
   join_container_
     ~len:(fun () -> n)
-    ~iter:(fun f () -> Array.iter f futs)
+    ~iter:(fun yield () ->
+      for i = 0 to n - 1 do
+        yield (spawn ~on (fun () -> f i))
+      done)
     ~map:(fun _f () -> ())
     ()