From 8770d4fb9c831af4077f5397e60715b6a56b4516 Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Tue, 11 Nov 2025 00:00:54 -0500
Subject: [PATCH] repro for #41

---
 Makefile                 |  8 ++++++
 examples/repro_41/dune   |  5 ++++
 examples/repro_41/run.ml | 54 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 67 insertions(+)
 create mode 100644 examples/repro_41/dune
 create mode 100644 examples/repro_41/run.ml

diff --git a/Makefile b/Makefile
index 8ca1e86a..0c140e18 100644
--- a/Makefile
+++ b/Makefile
@@ -67,6 +67,14 @@ bench-pi:
 		'./_build/default/benchs/pi.exe -n $(PI_NSTEPS) -j 16 -mode forkjoin -kind=pool' \
 		'./_build/default/benchs/pi.exe -n $(PI_NSTEPS) -j 20 -mode forkjoin -kind=pool'
 
+bench-repro-41:
+	dune build $(DUNE_OPTS_BENCH) examples/repro_41/run.exe
+	hyperfine --warmup=1 \
+		"./_build/default/examples/repro_41/run.exe 4 domainslib" \
+		"./_build/default/examples/repro_41/run.exe 4 moonpool" \
+		"./_build/default/examples/repro_41/run.exe 5 moonpool" \
+		"./_build/default/examples/repro_41/run.exe 5 seq"
+
 .PHONY: test clean bench-fib bench-pi
 
 VERSION=$(shell awk '/^version:/ {print $$2}' moonpool.opam)
diff --git a/examples/repro_41/dune b/examples/repro_41/dune
new file mode 100644
index 00000000..f6f84a6e
--- /dev/null
+++ b/examples/repro_41/dune
@@ -0,0 +1,5 @@
+(executables
+ (names run)
+ (enabled_if
+  (>= %{ocaml_version} 5.0))
+ (libraries moonpool trace trace-tef domainslib))
diff --git a/examples/repro_41/run.ml b/examples/repro_41/run.ml
new file mode 100644
index 00000000..769c663b
--- /dev/null
+++ b/examples/repro_41/run.ml
@@ -0,0 +1,54 @@
+(* fibo.ml *)
+let cutoff = 25
+let input = 40
+
+let rec fibo_seq n =
+  if n <= 1 then
+    n
+  else
+    fibo_seq (n - 1) + fibo_seq (n - 2)
+
+let rec fibo_domainslib ctx n =
+  if n <= cutoff then
+    fibo_seq n
+  else
+    let open Domainslib in
+    let fut1 = Task.async ctx (fun () -> fibo_domainslib ctx (n - 1)) in
+    let fut2 = Task.async ctx (fun () -> fibo_domainslib ctx (n - 2)) in
+    Task.await ctx fut1 + Task.await ctx fut2
+
+let rec fibo_moonpool ctx n =
+  if n <= cutoff then
+    fibo_seq n
+  else
+    let open Moonpool in
+    let fut1 = Fut.spawn ~on:ctx (fun () -> fibo_moonpool ctx (n - 1)) in
+    let fut2 = Fut.spawn ~on:ctx (fun () -> fibo_moonpool ctx (n - 2)) in
+    Fut.await fut1 + Fut.await fut2
+
+let usage =
+  "fibo.exe <num_domains> [ domainslib | moonpool | moonpool_fifo | seq ]"
+
+let num_domains = try int_of_string Sys.argv.(1) with _ -> failwith usage
+let implem = try Sys.argv.(2) with _ -> failwith usage
+
+let () =
+  let output =
+    match implem with
+    | "moonpool" ->
+      let open Moonpool in
+      let ctx = Ws_pool.create ~num_threads:num_domains () in
+      Ws_pool.run_wait_block ctx (fun () -> fibo_moonpool ctx input)
+    | "moonpool_fifo" ->
+      let open Moonpool in
+      let ctx = Fifo_pool.create ~num_threads:num_domains () in
+      Ws_pool.run_wait_block ctx (fun () -> fibo_moonpool ctx input)
+    | "domainslib" ->
+      let open Domainslib in
+      let pool = Task.setup_pool ~num_domains () in
+      Task.run pool (fun () -> fibo_domainslib pool input)
+    | "seq" -> fibo_seq input
+    | _ -> failwith usage
+  in
+  print_int output;
+  print_newline ()