From eaf71a2e7455965a18e78325885b97770c1488ec Mon Sep 17 00:00:00 2001
From: Rolf vandeVaart <rvandevaart@nvidia.com>
Date: Wed, 28 Feb 2007 21:38:02 +0000
Subject: [PATCH] Add simple test that sends a message between all the ranks in
 the job. Useful to prove a cluster is up and working.  Reviewed by Jeff
 Squyres.

This commit was SVN r13857.
---
 examples/Makefile         |  6 ++--
 examples/Makefile.include |  4 ++-
 examples/connectivity_c.c | 67 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 73 insertions(+), 4 deletions(-)
 create mode 100644 examples/connectivity_c.c

diff --git a/examples/Makefile b/examples/Makefile
index 83121e0cb2..321fd9a8a7 100644
--- a/examples/Makefile
+++ b/examples/Makefile
@@ -9,7 +9,7 @@
 #                         University of Stuttgart.  All rights reserved.
 # Copyright (c) 2004-2005 The Regents of the University of California.
 #                         All rights reserved.
-# Copyright (c) 2006      Sun Microsystems, Inc.  All rights reserved.
+# Copyright (c) 2006-2007 Sun Microsystems, Inc.  All rights reserved.
 # $COPYRIGHT$
 # 
 # Additional copyrights may follow
@@ -41,12 +41,12 @@ FCFLAGS = -g
 # Example programs to build
 
 EXAMPLES = hello_c hello_cxx hello_f77 hello_f90 \
-           ring_c ring_cxx ring_f77 ring_f90
+           ring_c ring_cxx ring_f77 ring_f90 connectivity_c
 
 # Default target.  Always build the C example.  Only build the others
 # if Open MPI was build with the relevant language bindings.
 
-all: hello_c ring_c
+all: hello_c ring_c connectivity_c
 	@ if test "`ompi_info --parsable | grep bindings:cxx:yes`" != ""; then \
 	    $(MAKE) hello_cxx ring_cxx; \
 	fi
diff --git a/examples/Makefile.include b/examples/Makefile.include
index 679e63c48d..724ccdf605 100644
--- a/examples/Makefile.include
+++ b/examples/Makefile.include
@@ -11,6 +11,7 @@
 # Copyright (c) 2004-2005 The Regents of the University of California.
 #                         All rights reserved.
 # Copyright (c) 2006      Cisco Systems, Inc.  All rights reserved.
+# Copyright (c) 2007      Sun Microsystems, Inc.  All rights reserved.
 # $COPYRIGHT$
 # 
 # Additional copyrights may follow
@@ -37,4 +38,5 @@ EXTRA_DIST += \
         examples/ring_c.c \
         examples/ring_cxx.cc \
         examples/ring_f77.f \
-        examples/ring_f90.f90
+        examples/ring_f90.f90 \
+        examples/connectivity_c.c
diff --git a/examples/connectivity_c.c b/examples/connectivity_c.c
new file mode 100644
index 0000000000..f52c8a301a
--- /dev/null
+++ b/examples/connectivity_c.c
@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2007      Sun Microsystems, Inc.  All rights reserved.
+ */
+
+/*
+ * Test the connectivity between all processes.
+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <netdb.h>
+#include <unistd.h>
+#include <mpi.h>
+
+int
+main(int argc, char **argv)
+{
+    MPI_Status  status;
+    int         verbose = 0;
+    int         rank;
+    int         np;        /* number of processes in job */
+    int         peer;
+    int         i;
+    int         j;
+    int         length;
+    char        name[MPI_MAX_PROCESSOR_NAME+1];
+
+    MPI_Init(&argc, &argv);
+    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+    MPI_Comm_size(MPI_COMM_WORLD, &np);
+
+    /*
+     * If we cannot get the name for whatever reason, just
+     * set it to unknown. */
+    if (MPI_SUCCESS != MPI_Get_processor_name(name, &length)) {
+        strcpy(name, "unknown");
+    }
+    
+    if (argc>1 && strcmp(argv[1], "-v")==0)
+        verbose = 1;
+
+    for (i=0; i<np; i++) {
+        if (rank==i) {
+            /* rank i sends to and receives from each higher rank */
+            for(j=i+1; j<np; j++) {
+                if (verbose)
+                    printf("checking connection between rank %d on %s and rank %-4d\n",
+                           i, name, j);
+                MPI_Send(&rank, 1, MPI_INT, j, rank, MPI_COMM_WORLD);
+                MPI_Recv(&peer, 1, MPI_INT, j, j, MPI_COMM_WORLD, &status);
+            }
+        } else if (rank>i) {
+            /* receive from and reply to rank i */
+            MPI_Recv(&peer, 1, MPI_INT, i, i, MPI_COMM_WORLD, &status);
+            MPI_Send(&rank, 1, MPI_INT, i, rank, MPI_COMM_WORLD);
+        }
+    }
+
+    MPI_Barrier(MPI_COMM_WORLD);
+    if (rank==0)
+        printf("Connectivity test on %d processes PASSED.\n", np);
+
+    MPI_Finalize();
+    return 0;
+}