>From 9f6330bcc336eae6aedc78f56c1ebbbf30ae0b2d Mon Sep 17 00:00:00 2001
From: Dave Love <address@hidden>
Date: Mon, 31 Jul 2017 14:54:29 +0100
Subject: [PATCH 2/8] gnu: Add openmpi-thread-multiple and modify openmpi
 accordingly.

thread-multiple support hurts performance even if it's not used.

* gnu/packages/mpi.scm (openmpi)[arguments]: Don't enable thread-multiple.
---
 gnu/packages/mpi.scm | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/gnu/packages/mpi.scm b/gnu/packages/mpi.scm
index 968eb8870..aa0b78237 100644
--- a/gnu/packages/mpi.scm
+++ b/gnu/packages/mpi.scm
@@ -133,7 +133,6 @@ bind processes, and much more.")
     (arguments
      `(#:configure-flags `("--enable-static"
 
-                           "--enable-mpi-thread-multiple"
                            "--enable-builtin-atomics"
 
                            "--enable-mpi-ext=all"
@@ -183,2 +182,18 @@ software vendors, application developers and computer science researchers.")
     ;; See file://LICENSE
     (license bsd-2)))
+
+(define-public openmpi-thread-multiple
+  (package
+    (inherit openmpi)
+    (name "openmpi-thread-multiple")
+    (arguments
+     (substitute-keyword-arguments (package-arguments openmpi)
+       ((#:configure-flags flags)
+        `(cons "--enable-mpi-thread-multiple" ,flags))))
+    (description (string-append (package-description openmpi)
+                                "\
+
+This version has an implementation of `MPI_Init_thread' that provides
+‘MPI_THREAD_MULTIPLE’.  This won't work correctly with all transports (e.g.
+openib), and the performance is generally worse than the vanilla openmpi
+package, which only provides ‘MPI_THREAD_FUNNELED’."))))

-- 
2.11.0