From 8f7cec22975b172500ce5e83ecdcc23aea6fb262 Mon Sep 17 00:00:00 2001
From: Jonathan Ringer <jonringer117@gmail.com>
Date: Tue, 17 Nov 2020 08:31:06 -0800
Subject: [PATCH] python3Packages.numpy: fix tests for >64 core machines

---
 pkgs/development/python-modules/numpy/default.nix | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/pkgs/development/python-modules/numpy/default.nix b/pkgs/development/python-modules/numpy/default.nix
index b8faccb155b5..622f784fb8ba 100644
--- a/pkgs/development/python-modules/numpy/default.nix
+++ b/pkgs/development/python-modules/numpy/default.nix
@@ -58,9 +58,13 @@ in buildPythonPackage rec {
     ./numpy-distutils-C++.patch
   ];
 
+  # we default openblas to build with 64 threads
+  # if a machine has more than 64 threads, it will segfault
+  # see https://github.com/xianyi/OpenBLAS/issues/2993
   preConfigure = ''
     sed -i 's/-faltivec//' numpy/distutils/system_info.py
     export NPY_NUM_BUILD_JOBS=$NIX_BUILD_CORES
+    export OMP_NUM_THREADS=$((NIX_BUILD_CORES > 64 ? 64 : NIX_BUILD_CORES))
   '';
 
   preBuild = ''