From a34e2f08d2ed6ff430eab6e9e9227869d04176de Mon Sep 17 00:00:00 2001
From: Daniel Arndt <daniel.arndt@iwr.uni-heidelberg.de>
Date: Sat, 28 Apr 2018 19:48:17 +0200
Subject: [PATCH] Add test

---
 tests/mpi/create_group_01.cc              | 58 +++++++++++++++++++++++
 tests/mpi/create_group_01.mpirun=3.output |  8 ++++
 2 files changed, 66 insertions(+)
 create mode 100644 tests/mpi/create_group_01.cc
 create mode 100644 tests/mpi/create_group_01.mpirun=3.output

diff --git a/tests/mpi/create_group_01.cc b/tests/mpi/create_group_01.cc
new file mode 100644
index 0000000000..15641517ea
--- /dev/null
+++ b/tests/mpi/create_group_01.cc
@@ -0,0 +1,58 @@
+// ---------------------------------------------------------------------
+//
+// Copyright (C) 2018 by the deal.II authors
+//
+// This file is part of the deal.II library.
+//
+// The deal.II library is free software; you can use it, redistribute
+// it, and/or modify it under the terms of the GNU Lesser General
+// Public License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+// The full text of the license can be found in the file LICENSE at
+// the top level of the deal.II distribution.
+//
+// ---------------------------------------------------------------------
+
+
+
+// check that Utilities::MPI::create_group is only collective over the group of
+// processes that actually want to create the communicator.
+// In p4est-2.0, sc_init() leads to a deadlock when MPI_Comm_create_group is
+// called (see https://github.com/cburstedde/p4est/issues/30). Hence, this test
+// also ensures that the treatment of sc_init() is appropriate.
+
+#include "../tests.h"
+
+int main(int argc, char *argv[])
+{
+  Utilities::MPI::MPI_InitFinalize mpi_init (argc, argv, 1);
+  MPILogInitAll log_all;
+
+  const MPI_Comm global_comm = MPI_COMM_WORLD;
+
+  const unsigned int my_id = Utilities::MPI::this_mpi_process(global_comm);
+  const unsigned int n_ranks = Utilities::MPI::n_mpi_processes(global_comm);
+
+  // Get the group of processes in MPI_COMM_WORLD
+  MPI_Group world_group;
+  int ierr = MPI_Comm_group(MPI_COMM_WORLD, &world_group);
+  AssertThrowMPI(ierr);
+
+  const int n = n_ranks/2;
+  std::vector<int> ranks;
+  for (unsigned int i=0; i<n_ranks; i+=2)
+    ranks.push_back(i);
+
+  // Construct a group containing all of the even ranks in world_group
+  MPI_Group even_group;
+  ierr = MPI_Group_incl(world_group, n, ranks.data(), &even_group);
+  AssertThrowMPI(ierr);
+
+  if (my_id%2==0)
+    {
+      MPI_Comm group_comm;
+      ierr = Utilities::MPI::create_group(global_comm, even_group, 0, &group_comm);
+      AssertThrowMPI(ierr);
+    }
+  deallog << "OK" << std::endl;
+}
diff --git a/tests/mpi/create_group_01.mpirun=3.output b/tests/mpi/create_group_01.mpirun=3.output
new file mode 100644
index 0000000000..3342d14fa8
--- /dev/null
+++ b/tests/mpi/create_group_01.mpirun=3.output
@@ -0,0 +1,8 @@
+
+DEAL:0::OK
+
+DEAL:1::OK
+
+
+DEAL:2::OK
+
-- 
2.39.5