From c6f039e59cda597af3165ebfdf3a9147c095c2a1 Mon Sep 17 00:00:00 2001
From: Markus Kowalewski <markus.kowalewski@fysik.su.se>
Date: Thu, 7 Feb 2019 13:34:06 +0100
Subject: [PATCH] openmpi: add patch for mpi tests on machines with less than 4
 cores

Fix a bug that ignores OMPI_MCA_rmaps_base_oversubscribe (upstream patch).
This bug breaks the test from libs, such as scalapack,
on machines with less than 4 cores.
---
 pkgs/development/libraries/openmpi/default.nix | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/pkgs/development/libraries/openmpi/default.nix b/pkgs/development/libraries/openmpi/default.nix
index b3f17021606..cd60e0edca1 100644
--- a/pkgs/development/libraries/openmpi/default.nix
+++ b/pkgs/development/libraries/openmpi/default.nix
@@ -1,5 +1,5 @@
-{ stdenv, fetchurl, gfortran, perl, libnl, rdma-core, zlib
-, numactl, libevent, hwloc
+{ stdenv, fetchurl, fetchpatch, gfortran, perl, libnl
+, rdma-core, zlib, numactl, libevent, hwloc
 
 # Enable the Sun Grid Engine bindings
 , enableSGE ? false
@@ -19,6 +19,14 @@ in stdenv.mkDerivation rec {
     sha256 = "0srnjwzsmyhka9hhnmqm86qck4w3xwjm8g6sbns58wzbrwv8l2rg";
   };
 
+  patches = [ (fetchpatch {
+   # Fix a bug that ignores OMPI_MCA_rmaps_base_oversubscribe (upstream patch).
+   # This bug breaks the test from libs, such as scalapack,
+   # on machines with less than 4 cores.
+   url = https://github.com/open-mpi/ompi/commit/98c8492057e6222af6404b352430d0dd7553d253.patch;
+   sha256 = "1mpd8sxxprgfws96qqlzvqf58pn2vv2d0qa8g8cpv773sgw3b3gj";
+  }) ];
+
   postPatch = ''
     patchShebangs ./
   '';