test/mpi: Add local only sessions init test

Add a test to verify the local only behavior of MPI_Session_init. To do
so, we launch an extra process via mpiexec that will never call
MPI_Session_init.

Author: raffenet

test/mpi/.gitignore

@@ -1530,6 +1530,7 @@
 /session/session_psets
 /session/session_self
 /session/session_bsend
+/session/session_local_only
 /spawn/concurrent_spawns
 /spawn/disconnect
 /spawn/disconnect2

test/mpi/session/Makefile.am

@@ -16,7 +16,8 @@ noinst_PROGRAMS = \
     session_re_init \
     session_psets \
     session_self \
-    session_bsend
+    session_bsend \
+    session_local_only
 
 session_mult_init_SOURCES = session.c
 session_mult_init_CPPFLAGS = -DMULT_INIT $(AM_CPPFLAGS)

test/mpi/session/session_local_only.c

@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) by Argonne National Laboratory
+ *     See COPYRIGHT in top-level directory
+ */
+
+#include "mpi.h"
+#include "stdio.h"
+
+/*
+static char MTEST_Descrip[] = "Test MPI Sessions local-only behavior.
+No communication is performed. Intended to run with a minimum of 2 MPI
+processes and at least 1 non-MPI process. This verifies the local,
+non-collective nature of MPI Sessions initialization and group
+construction APIs. Example launch command:
+
+  mpiexec -n 2 ./session_local_only : -n 1 true
+
+The world group size will be 3, but only 2 processes will initialize
+and make MPI calls. An correct implementation should not hang.
+*/
+
+int main(int argc, char *argv[])
+{
+    MPI_Session session;
+    MPI_Group group;
+    int rank, size;
+
+    MPI_Session_init(MPI_INFO_NULL, MPI_ERRORS_RETURN, &session);
+
+    MPI_Group_from_session_pset(session, "mpi://world", &group);
+    MPI_Group_rank(group, &rank);
+    MPI_Group_size(group, &size);
+    if (size < 3) {
+        /* no communicator so directly call errhandler */
+        MPI_Session_call_errhandler(session, 1);
+    }
+
+    MPI_Group_free(&group);
+    MPI_Session_finalize(&session);
+    if (rank == 0) {
+        printf("No Errors\n");
+    }
+
+    return 0;
+}

test/mpi/session/testlist

@@ -5,3 +5,5 @@ session_re_init 4
 session_psets 1
 session_self 1
 session_bsend 2
+# args to session_local_only append ": -n 1 true" to mpiexec
+session_local_only 2 timeLimit=10 arg=: arg=-n arg=1 arg=true