From 9503adb6660010f132f5574a4d0233aff067367d Mon Sep 17 00:00:00 2001
From: Martin Weinelt <hexa@darmstadt.ccc.de>
Date: Fri, 30 Sep 2022 13:09:56 +0200
Subject: [PATCH] python3Packages.scipy: Limit OpenMP threads during check
 phase

The scipy tests already run in parallel and the openmp threads come on
top of that. That overloads machines very easily and therefore we
introduce a scaling limit to the number of openmp threads used.

https://www.openmp.org/spec-html/5.0/openmpse50.html
---
 pkgs/development/python-modules/scipy/default.nix | 1 +
 1 file changed, 1 insertion(+)

diff --git a/pkgs/development/python-modules/scipy/default.nix b/pkgs/development/python-modules/scipy/default.nix
index aa578d21d257..e791454b9018 100644
--- a/pkgs/development/python-modules/scipy/default.nix
+++ b/pkgs/development/python-modules/scipy/default.nix
@@ -54,6 +54,7 @@ buildPythonPackage rec {
   checkPhase = ''
     runHook preCheck
     pushd "$out"
+    export OMP_NUM_THREADS=$(( $NIX_BUILD_CORES / 4 ))
     ${python.interpreter} -c "import scipy; scipy.test('fast', verbose=10, parallel=$NIX_BUILD_CORES)"
     popd
     runHook postCheck