From 0c1e4facb8761f9993f10fa858ca7abdc13143e8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20Robert?= <cr52@protonmail.com>
Date: Sun, 24 Mar 2024 18:11:09 +0100
Subject: [PATCH] BUG: avoid multiprocessing overhead when looping on a single
 worker

---
 nonos/main.py          | 20 ++++++++++++--------
 tests/test_plotting.py |  2 +-
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/nonos/main.py b/nonos/main.py
index 1f1d9443..03c852ce 100644
--- a/nonos/main.py
+++ b/nonos/main.py
@@ -46,7 +46,7 @@
     import importlib_resources
 
 
-# process function for parallisation purpose with progress bar
+# process function for parallelisation purpose with progress bar
 # counterParallel = Value('i', 0) # initialization of a counter
 def process_field(
     on,
@@ -540,14 +540,18 @@ def mytrack(iterable, *args, **kwargs):  # noqa: ARG001
 
     logger.info("Starting main loop")
     tstart = time.time()
-    with Pool(ncpu) as pool:
-        list(
-            mytrack(
-                pool.imap(func, args["on"]),
-                description="Processing snapshots",
-                total=len(args["on"]),
+    if ncpu == 1:
+        for on in args["on"]:
+            func(on)
+    else:
+        with Pool(ncpu) as pool:
+            list(
+                mytrack(
+                    pool.imap(func, args["on"]),
+                    description="Processing snapshots",
+                    total=len(args["on"]),
+                )
             )
-        )
     if not show:
         logger.info("Operation took {:.2f}s", time.time() - tstart)
 
diff --git a/tests/test_plotting.py b/tests/test_plotting.py
index e33852d3..1409cd71 100644
--- a/tests/test_plotting.py
+++ b/tests/test_plotting.py
@@ -190,7 +190,7 @@ def test_pbar(simulation_dir, capsys, tmp_path):
 
     out, err = capsys.readouterr()
     assert err == ""
-    assert "Processing snapshots" in out
+    assert out == ""
     assert ret == 0