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Mpi examples

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# OpenMPI Sample Applications
Sample MPI applications provided both as a trivial primer to MPI as well as simple tests to ensure that your Open MPI installation is working properly.
## Examples
There are two MPI examples, each using one of six different MPI interfaces:
**Hello world**
* C: [hello_c.c](../../src/ompi/hello_c.c)
* C++: [hello_cxx.cc](../../src/ompi/hello_cxx.cc)
* Fortran mpif.h: [hello_mpifh.f](../../src/ompi/hello_mpifh.f)
* Fortran use mpi: [hello_usempi.f90](../../src/ompi/hello_usempi.f90)
* Fortran use mpi_f08: [hello_usempif08.f90](../../src/ompi/hello_usempif08.f90)
* Java: [Hello.java](../../src/ompi/Hello.java)
* C shmem.h: [hello_oshmem_c.c](../../src/ompi/hello_oshmem_c.c)
* Fortran shmem.fh: [hello_oshmemfh.f90](../../src/ompi/hello_oshmemfh.f90)
**Send a trivial message around in a ring**
* C: [ring_c.c](../../src/ompi/ring_c.c)
* C++: [ring_cxx.cc](../../src/ompi/ring_cxx.cc)
* Fortran mpif.h: [ring_mpifh.f](../../src/ompi/ring_mpifh.f)
* Fortran use mpi: [ring_usempi.f90](../../src/ompi/ring_usempi.f90)
* Fortran use mpi_f08: [ring_usempif08.f90](../../src/ompi/ring_usempif08.f90)
* Java: [Ring.java](../../src/ompi/Ring.java)
* C shmem.h: [ring_oshmem_c.c](../../src/ompi/ring_oshmem_c.c)
* Fortran shmem.fh: [ring_oshmemfh.f90](../../src/ompi/ring_oshmemfh.f90)
Additionally, there's one further example application, but this one only uses the MPI C bindings:
**Test the connectivity between all processes**
* C: [connectivity_c.c](../../src/ompi/connectivity_c.c)
## Build Examples
Download [examples](../../src/ompi/ompi.tar.gz).
The Makefile in this directory will build the examples for the supported languages (e.g., if you do not have the Fortran "use mpi" bindings compiled as part of Open MPI, those examples will be skipped).
The Makefile assumes that the wrapper compilers mpicc, mpic++, and mpifort are in your path.
Although the Makefile is tailored for Open MPI (e.g., it checks the *mpi_info* command to see if you have support for C++, mpif.h, use mpi, and use mpi_f08 F90), all of the example programs are pure MPI, and therefore not specific to Open MPI. Hence, you can use a different MPI implementation to compile and run these programs if you wish.
```console
[login@cn204.anselm ]$ tar xvf ompi.tar.gz
./
./connectivity_c.c
./Hello.java
./ring_mpifh.f
./hello_oshmem_cxx.cc
...
...
./hello_cxx.cc
[login@cn204.anselm ]$ ml OpenMPI/2.1.1-GCC-6.3.0-2.27
[login@cn204.anselm ]$ make
mpicc -g hello_c.c -o hello_c
mpicc -g ring_c.c -o ring_c
mpicc -g connectivity_c.c -o connectivity_c
mpicc -g spc_example.c -o spc_example
mpic++ -g hello_cxx.cc -o hello_cxx
mpic++ -g ring_cxx.cc -o ring_cxx
mpifort -g hello_mpifh.f -o hello_mpifh
mpifort -g ring_mpifh.f -o ring_mpifh
mpifort -g hello_usempi.f90 -o hello_usempi
mpifort -g ring_usempi.f90 -o ring_usempi
mpifort -g hello_usempif08.f90 -o hello_usempif08
mpifort -g ring_usempif08.f90 -o ring_usempif08
mpijavac Hello.java
mpijavac Ring.java
shmemcc -g hello_oshmem_c.c -o hello_oshmem
shmemc++ -g hello_oshmem_cxx.cc -o hello_oshmemcxx
shmemcc -g ring_oshmem_c.c -o ring_oshmem
shmemcc -g oshmem_shmalloc.c -o oshmem_shmalloc
shmemcc -g oshmem_circular_shift.c -o oshmem_circular_shift
shmemcc -g oshmem_max_reduction.c -o oshmem_max_reduction
shmemcc -g oshmem_strided_puts.c -o oshmem_strided_puts
shmemcc -g oshmem_strided_puts.c -o oshmem_strided_puts
shmemcc -g oshmem_symmetric_data.c -o oshmem_symmetric_data
shmemfort -g hello_oshmemfh.f90 -o hello_oshmemfh
shmemfort -g ring_oshmemfh.f90 -o ring_oshmemfh
[login@cn204.anselm ]$ find . -executable -type f
./hello_oshmem
./dtrace/myppriv.sh
./dtrace/partrace.sh
./oshmem_shmalloc
./ring_cxx
./ring_usempi
./hello_mpifh
./hello_cxx
./oshmem_max_reduction
./oshmem_symmetric_data
./oshmem_strided_puts
./hello_usempif08
./ring_usempif08
./spc_example
./hello_oshmemfh
./ring_oshmem
./oshmem_circular_shift
./hello_c
./ring_c
./hello_usempi
./ring_oshmemfh
./connectivity_c
./ring_mpifh
```
/*
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
/*
* Author of revised version: Franklyn Pinedo
*
* Adapted from Source Code in C of Tutorial/User's Guide for MPI by
* Peter Pacheco.
*/
/*
* Copyright (c) 2011 Cisco Systems, Inc. All rights reserved.
*
*/
import mpi.*;
class Hello {
static public void main(String[] args) throws MPIException {
MPI.Init(args);
int myrank = MPI.COMM_WORLD.getRank();
int size = MPI.COMM_WORLD.getSize() ;
System.out.println("Hello world from rank " + myrank + " of " + size);
MPI.Finalize();
}
}
/*
* Copyright (c) 2011 Cisco Systems, Inc. All rights reserved.
*
* Simple ring test program
*/
import mpi.* ;
class Ring {
static public void main(String[] args) throws MPIException {
MPI.Init(args) ;
int source; // Rank of sender
int dest; // Rank of receiver
int tag=50; // Tag for messages
int next;
int prev;
int message[] = new int [1];
int myrank = MPI.COMM_WORLD.getRank() ;
int size = MPI.COMM_WORLD.getSize() ;
/* Calculate the rank of the next process in the ring. Use the
modulus operator so that the last process "wraps around" to
rank zero. */
next = (myrank + 1) % size;
prev = (myrank + size - 1) % size;
/* If we are the "master" process (i.e., MPI_COMM_WORLD rank 0),
put the number of times to go around the ring in the
message. */
if (0 == myrank) {
message[0] = 10;
System.out.println("Process 0 sending " + message[0] + " to rank " + next + " (" + size + " processes in ring)");
MPI.COMM_WORLD.send(message, 1, MPI.INT, next, tag);
}
/* Pass the message around the ring. The exit mechanism works as
follows: the message (a positive integer) is passed around the
ring. Each time it passes rank 0, it is decremented. When
each processes receives a message containing a 0 value, it
passes the message on to the next process and then quits. By
passing the 0 message first, every process gets the 0 message
and can quit normally. */
while (true) {
MPI.COMM_WORLD.recv(message, 1, MPI.INT, prev, tag);
if (0 == myrank) {
--message[0];
System.out.println("Process 0 decremented value: " + message[0]);
}
MPI.COMM_WORLD.send(message, 1, MPI.INT, next, tag);
if (0 == message[0]) {
System.out.println("Process " + myrank + " exiting");
break;
}
}
/* The last process does one extra send to process 0, which needs
to be received before the program can exit */
if (0 == myrank) {
MPI.COMM_WORLD.recv(message, 1, MPI.INT, prev, tag);
}
MPI.Finalize();
}
}
/*
* 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;
}
/*
* Copyright (c) 2004-2006 The Trustees of Indiana University and Indiana
* University Research and Technology
* Corporation. All rights reserved.
* Copyright (c) 2006 Cisco Systems, Inc. All rights reserved.
*
* Sample MPI "hello world" application in C
*/
#include <stdio.h>
#include "mpi.h"
int main(int argc, char* argv[])
{
int rank, size, len;
char version[MPI_MAX_LIBRARY_VERSION_STRING];
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
MPI_Comm_size(MPI_COMM_WORLD, &size);
MPI_Get_library_version(version, &len);
printf("Hello, world, I am %d of %d, (%s, %d)\n",
rank, size, version, len);
MPI_Finalize();
return 0;
}
//
// Copyright (c) 2004-2006 The Trustees of Indiana University and Indiana
// University Research and Technology
// Corporation. All rights reserved.
// Copyright (c) 2006 Cisco Systems, Inc. All rights reserved.
//
// Sample MPI "hello world" application in C++
//
// NOTE: The MPI C++ bindings were deprecated in MPI-2.2 and removed
// from the standard in MPI-3. Open MPI still provides C++ MPI
// bindings, but they are no longer built by default (and may be
// removed in a future version of Open MPI). You must
// --enable-mpi-cxx when configuring Open MPI to enable the MPI C++
// bindings.
//
#include "mpi.h"
#include <iostream>
int main(int argc, char **argv)
{
int rank, size, len;
char version[MPI_MAX_LIBRARY_VERSION_STRING];
MPI::Init();
rank = MPI::COMM_WORLD.Get_rank();
size = MPI::COMM_WORLD.Get_size();
MPI_Get_library_version(version, &len);
std::cout << "Hello, world! I am " << rank << " of " << size
<< "(" << version << ", " << len << ")" << std::endl;
MPI::Finalize();
return 0;
}
C
C Copyright (c) 2004-2006 The Trustees of Indiana University and Indiana
C University Research and Technology
C Corporation. All rights reserved.
C Copyright (c) 2006-2015 Cisco Systems, Inc. All rights reserved.
C $COPYRIGHT$
C
C Sample MPI "hello world" application using the Fortran mpif.h
C bindings.
C
program main
implicit none
include 'mpif.h'
integer ierr, rank, size, len
character(len=MPI_MAX_LIBRARY_VERSION_STRING) version
call MPI_INIT(ierr)
call MPI_COMM_RANK(MPI_COMM_WORLD, rank, ierr)
call MPI_COMM_SIZE(MPI_COMM_WORLD, size, ierr)
call MPI_GET_LIBRARY_VERSION(version, len, ierr)
write(*, '("Hello, world, I am ", i2, " of ", i2, ": ", a)')
& rank, size, version
call MPI_FINALIZE(ierr)
end
/*
* Copyright (c) 2014 Mellanox Technologies, Inc.
* All rights reserved.
* Copyright (c) 2015 Cisco Systems, Inc. All rights reserved.
* $COPYRIGHT$
*
* Additional copyrights may follow
*
* $HEADER$
*/
#include <stdio.h>
#include "shmem.h"
#if !defined(OSHMEM_SPEC_VERSION) || OSHMEM_SPEC_VERSION < 10200
#error This application uses API 1.2 and up
#endif
int main(int argc, char* argv[])
{
int proc, nproc;
char name[SHMEM_MAX_NAME_LEN];
int major, minor;
shmem_init();
nproc = shmem_n_pes();
proc = shmem_my_pe();
shmem_info_get_name(name);
shmem_info_get_version(&major, &minor);
printf("Hello, world, I am %d of %d: %s (version: %d.%d)\n",
proc, nproc, name, major, minor);
shmem_finalize();
return 0;
}
/*
* Copyright (c) 2014 Mellanox Technologies, Inc.
* All rights reserved.
* Copyright (c) 2015 Cisco Systems, Inc. All rights reserved.
* Copyright (c) 2017 Research Organization for Information Science
* and Technology (RIST). All rights reserved.
* $COPYRIGHT$
*
* Additional copyrights may follow
*
* $HEADER$
*/
#include <iostream>
#include "shmem.h"
#if !defined(OSHMEM_SPEC_VERSION) || OSHMEM_SPEC_VERSION < 10200
#error This application uses API 1.2 and up
#endif
int main(int argc, char* argv[])
{
int proc, nproc;
char name[SHMEM_MAX_NAME_LEN];
int major, minor;
shmem_init();
nproc = shmem_n_pes();
proc = shmem_my_pe();
shmem_info_get_name(name);
shmem_info_get_version(&major, &minor);
std::cout << "Hello, world, I am " << proc << " of " << nproc << ": " << name
<< " (version: " << major << "." << minor << ")" << std::endl;
shmem_finalize();
return 0;
}
!
! Copyright (c) 2014 Mellanox Technologies, Inc.
! All rights reserved.
! Copyright (c) 2014-2015 Cisco Systems, Inc. All rights reserved.
! $COPYRIGHT$
!
! Additional copyrights may follow
!
! $HEADER$
!
program hello_oshmem
implicit none
include 'shmem.fh'
integer proc, nproc
integer shmem_my_pe, shmem_n_pes
integer major, minor, len
character(len=SHMEM_MAX_NAME_LEN) name
call SHMEM_INIT()
proc = SHMEM_MY_PE()
nproc = SHMEM_N_PES()
call SHMEM_INFO_GET_VERSION(major, minor)
call SHMEM_INFO_GET_NAME(name)
write(*, '("Hello, world, I am ", i2, " of ", i2, ": (version: ", i0, ".", i0, ")")') proc, nproc, major, minor
call SHMEM_FINALIZE()
end program hello_oshmem
!
! Copyright (c) 2004-2006 The Trustees of Indiana University and Indiana
! University Research and Technology
! Corporation. All rights reserved.
! Copyright (c) 2004-2005 The Regents of the University of California.
! All rights reserved.
! Copyright (c) 2006-2015 Cisco Systems, Inc. All rights reserved.
! $COPYRIGHT$
!
! Sample MPI "hello world" application using the Fortran mpi module
! bindings.
!
program main
use mpi
implicit none
integer :: ierr, rank, size, len
character(len=MPI_MAX_LIBRARY_VERSION_STRING) :: version
call MPI_INIT(ierr)
call MPI_COMM_RANK(MPI_COMM_WORLD, rank, ierr)
call MPI_COMM_SIZE(MPI_COMM_WORLD, size, ierr)
call MPI_GET_LIBRARY_VERSION(version, len, ierr)
write(*, '("Hello, world, I am ", i2, " of ", i2, ": ", a)') &
rank, size, version
call MPI_FINALIZE(ierr)
end
! -*- f90 -*-
!
! Copyright (c) 2004-2006 The Trustees of Indiana University and Indiana
! University Research and Technology
! Corporation. All rights reserved.
! Copyright (c) 2004-2005 The Regents of the University of California.
! All rights reserved.
! Copyright (c) 2006-2015 Cisco Systems, Inc. All rights reserved.
! Copyright (c) 2009-2012 Los Alamos National Security, LLC.
! All rights reserved.
! $COPYRIGHT$
!
! Sample MPI "hello world" application using the Fortran mpi_f08
! module bindings.
!
program main
use mpi_f08
implicit none
integer :: rank, size, len
character(len=MPI_MAX_LIBRARY_VERSION_STRING) :: version
call MPI_INIT()
call MPI_COMM_RANK(MPI_COMM_WORLD, rank)
call MPI_COMM_SIZE(MPI_COMM_WORLD, size)
call MPI_GET_LIBRARY_VERSION(version, len)
write(*, '("Hello, world, I am ", i2, " of ", i2, ": ", a)') &
rank, size, version
call MPI_FINALIZE()
end
File added
/*
* Copyright (c) 2014-2016 Mellanox Technologies, Inc.
* All rights reserved.
* $COPYRIGHT$
*
* Additional copyrights may follow
*
* $HEADER$
*/
#include <stdio.h>
#include <shmem.h>
int main (void)
{
static int aaa, bbb;
int num_pes, my_pe, peer;
shmem_init();
num_pes = shmem_n_pes();
my_pe = shmem_my_pe();
peer = (my_pe + 1) % num_pes;
printf("Process %d gets message from %d (%d processes in ring)\n", my_pe, peer, num_pes);
shmem_int_get(&aaa, &bbb, 1, peer);
shmem_barrier_all();
printf("Process %d exiting\n", my_pe);
shmem_finalize();
return 0;
}
/*
* Copyright (c) 2014-2016 Mellanox Technologies, Inc.
* All rights reserved.
* $COPYRIGHT$
*
* Additional copyrights may follow
*
* $HEADER$
*
* reduce [0,1,2] + _my_pe() across 4 PEs with MAX()
*/
#include <stdio.h>
#include <string.h>
#include <shmem.h>
long pSync[_SHMEM_BCAST_SYNC_SIZE];
#define N 3
long src[N];
long dst[N];
long pWrk[_SHMEM_REDUCE_SYNC_SIZE];
int main(void)
{
int i;
int my_pe, num_pes;
for (i = 0; i < SHMEM_BCAST_SYNC_SIZE; i += 1) {
pSync[i] = _SHMEM_SYNC_VALUE;
}
shmem_init();
my_pe = shmem_my_pe();
num_pes = shmem_n_pes();
for (i = 0; i < N; i += 1) {
src[i] = my_pe + i;
}
shmem_barrier_all();
shmem_long_max_to_all(dst, src, N, 0, 0, num_pes, pWrk, pSync);
printf("%d/%d dst =", my_pe, num_pes);
for (i = 0; i < N; i+= 1) {
printf(" %ld", dst[i]);
}
printf("\n");
shmem_finalize();
return 0;
}
/*
* Copyright (c) 2014-2016 Mellanox Technologies, Inc.
* All rights reserved.
* $COPYRIGHT$
*
* Additional copyrights may follow
*
* $HEADER$
*
* This sample allocates (shmalloc) symmetric memory (1 long integer),
* and then frees it. Success of allocation is not checked.
*
* Produces no output.
*/
#include <shmem.h>
int main(void)
{
long *x;
shmem_init();
x = (long *) shmem_malloc(sizeof(*x));
shmem_free(x);
shmem_finalize();
}
/*
* Copyright (c) 2014-2016 Mellanox Technologies, Inc.
* All rights reserved.
* $COPYRIGHT$
*
* Additional copyrights may follow
*
* $HEADER$
*
* This program is an adaptation of examples found in the man pages
* of SGI’s SHMEM implementation.
*
* In this program, iput is used to select 5 elements from array source separated by
* a stride of 2 and write them to array target using a stride of 1.
*
* Given the array source = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }
* iput will select 5 elements from array source on PE 0, using a stride of 2:
*
* selected elements = { 1, 3, 5, 7, 9 }
*
* These elements will then be written to the array source on PE 1 using a stride of 1:
*
* target = { 1, 3, 5, 7, 9 }
*
*/
#include <stdio.h>
#include <shmem.h>
int main(void)
{
short source[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
static short target[10];
int me;
shmem_init();
me = shmem_my_pe();
if (me == 0) {
/* put 10 words into target on PE 1 */
shmem_short_iput(target, source, 1, 2, 5, 1);
}
shmem_barrier_all(); /* sync sender and receiver */
if (me == 1) {
printf("target on PE %d is %hd %hd %hd %hd %hd\n", me,
target[0], target[1], target[2],
target[3], target[4] );
}
shmem_barrier_all(); /* sync before exiting */
shmem_finalize();
return 0;
}
/*
* Copyright (c) 2014-2016 Mellanox Technologies, Inc.
* All rights reserved.
* $COPYRIGHT$
*
* Additional copyrights may follow
*
* $HEADER$
*/
#include <stdio.h>
#include <shmem.h>
#define SIZE 16
int main(int argc, char* argv[])
{
short source[SIZE];
static short target[SIZE];
int i;
int num_pe, my_pe;
shmem_init();
num_pe = shmem_n_pes();
my_pe = shmem_my_pe();
if (my_pe == 0) {
/* initialize array */
for(i = 0; i < SIZE; i++) {
source[i] = i;
}
/* local, not symmetric */
/* static makes it symmetric */
/* put "size" words into target on each PE */
for(i = 1; i < num_pe; i++) {
shmem_short_put(target, source, SIZE, i);
}
}
shmem_barrier_all(); /* sync sender and receiver */
if (my_pe != 0) {
printf("Target on PE %d is \t", my_pe);
for(i = 0; i < SIZE; i++) {
printf("%hd \t", target[i]);
}
printf("\n");
}
shmem_barrier_all(); /* sync before exiting */
shmem_finalize();
return 0;
}
/*
* Copyright (c) 2004-2006 The Trustees of Indiana University and Indiana
* University Research and Technology
* Corporation. All rights reserved.
* Copyright (c) 2006 Cisco Systems, Inc. All rights reserved.
*
* Simple ring test program in C.
*/
#include <stdio.h>
#include "mpi.h"
int main(int argc, char *argv[])
{
int rank, size, next, prev, message, tag = 201;
/* Start up MPI */
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
MPI_Comm_size(MPI_COMM_WORLD, &size);
/* Calculate the rank of the next process in the ring. Use the
modulus operator so that the last process "wraps around" to
rank zero. */
next = (rank + 1) % size;
prev = (rank + size - 1) % size;
/* If we are the "master" process (i.e., MPI_COMM_WORLD rank 0),
put the number of times to go around the ring in the
message. */
if (0 == rank) {
message = 10;
printf("Process 0 sending %d to %d, tag %d (%d processes in ring)\n",
message, next, tag, size);
MPI_Send(&message, 1, MPI_INT, next, tag, MPI_COMM_WORLD);
printf("Process 0 sent to %d\n", next);
}
/* Pass the message around the ring. The exit mechanism works as
follows: the message (a positive integer) is passed around the
ring. Each time it passes rank 0, it is decremented. When
each processes receives a message containing a 0 value, it
passes the message on to the next process and then quits. By
passing the 0 message first, every process gets the 0 message
and can quit normally. */
while (1) {
MPI_Recv(&message, 1, MPI_INT, prev, tag, MPI_COMM_WORLD,
MPI_STATUS_IGNORE);
if (0 == rank) {
--message;
printf("Process 0 decremented value: %d\n", message);
}
MPI_Send(&message, 1, MPI_INT, next, tag, MPI_COMM_WORLD);
if (0 == message) {
printf("Process %d exiting\n", rank);
break;
}
}
/* The last process does one extra send to process 0, which needs
to be received before the program can exit */
if (0 == rank) {
MPI_Recv(&message, 1, MPI_INT, prev, tag, MPI_COMM_WORLD,
MPI_STATUS_IGNORE);
}
/* All done */
MPI_Finalize();
return 0;
}
//
// Copyright (c) 2004-2006 The Trustees of Indiana University and Indiana
// University Research and Technology
// Corporation. All rights reserved.
// Copyright (c) 2006 Cisco Systems, Inc. All rights reserved.
//
// Simple ring test program in C++.
//
// NOTE: The MPI C++ bindings were deprecated in MPI-2.2 and removed
// from the standard in MPI-3. Open MPI still provides C++ MPI
// bindings, but they are no longer built by default (and may be
// removed in a future version of Open MPI). You must
// --enable-mpi-cxx when configuring Open MPI to enable the MPI C++
// bindings.
//
#include "mpi.h"
#include <iostream>
int main(int argc, char *argv[])
{
int rank, size, next, prev, message, tag = 201;
// Start up MPI
MPI::Init();
rank = MPI::COMM_WORLD.Get_rank();
size = MPI::COMM_WORLD.Get_size();
// Calculate the rank of the next process in the ring. Use the
// modulus operator so that the last process "wraps around" to
// rank zero.
next = (rank + 1) % size;
prev = (rank + size - 1) % size;
// If we are the "master" process (i.e., MPI_COMM_WORLD rank 0),
// put the number of times to go around the ring in the message.
if (0 == rank) {
message = 10;
std::cout << "Process 0 sending " << message << " to " << next
<< ", tag " << tag << " (" << size << " processes in ring)"
<< std::endl;
MPI::COMM_WORLD.Send(&message, 1, MPI::INT, next, tag);
std::cout << "Process 0 sent to " << next << std::endl;
}
// Pass the message around the ring. The exit mechanism works as
// follows: the message (a positive integer) is passed around the
// ring. Each time it passes rank 0, it is decremented. When
// each processes receives a message containing a 0 value, it
// passes the message on to the next process and then quits. By
// passing the 0 message first, every process gets the 0 message
// and can quit normally.
while (1) {
MPI::COMM_WORLD.Recv(&message, 1, MPI::INT, prev, tag);
if (0 == rank) {
--message;
std::cout << "Process 0 decremented value: " << message
<< std::endl;
}
MPI::COMM_WORLD.Send(&message, 1, MPI::INT, next, tag);
if (0 == message) {
std::cout << "Process " << rank << " exiting" << std::endl;
break;
}
}
// The last process does one extra send to process 0, which needs
// to be received before the program can exit */
if (0 == rank) {
MPI::COMM_WORLD.Recv(&message, 1, MPI::INT, prev, tag);
}
// All done
MPI::Finalize();
return 0;
}
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