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/* A simple example ping-pong program to test MPI_Send and MPI_Recv */
/* Copyright (c) 2009-2025. The SimGrid Team. All rights reserved. */
/* This program is free software; you can redistribute it and/or modify it
* under the terms of the license (GNU LGPL) which comes with this package. */
#include <stdio.h>
#include <mpi.h>
/* This test performs a simple pingpong between 2 processes
Each process calls smpi_execute or smpi_execute_flops */
int main(int argc, char *argv[])
{
const int tag1 = 42;
const int tag2 = 43; /* Message tag */
int size;
int rank;
int msg = 99;
MPI_Status status;
int err = MPI_Init(&argc, &argv); /* Initialize MPI */
if (err != MPI_SUCCESS) {
printf("MPI initialization failed!\n");
exit(1);
}
MPI_Comm_size(MPI_COMM_WORLD, &size); /* Get nr of tasks */
MPI_Comm_rank(MPI_COMM_WORLD, &rank); /* Get id of this process */
if (size != 2) {
printf("run this program with exactly 2 processes (-np 2)\n");
MPI_Finalize();
exit(0);
}
if (rank == 0) {
printf("\n *** Ping-pong test (MPI_Send/MPI_Recv) ***\n\n");
/* start ping-pong tests between several pairs */
int dst = 1;
printf("[%d] About to send 1st message '%d' to process [%d]\n", rank, msg, dst);
MPI_Send(&msg, 1, MPI_INT, dst, tag1, MPI_COMM_WORLD);
/* Inject five seconds of fake computation time */
/* We are in a public file, not internal to SimGrid, so _benched flavour is preferred, as it protects against
* accidental skip */
/* smpi_execute_benched here is mostly equivalent to sleep, which is intercepted by smpi and turned into smpi_sleep
*/
/* Difference with sleep is only for energy consumption */
smpi_execute_benched(5.0);
MPI_Recv(&msg, 1, MPI_INT, dst, tag2, MPI_COMM_WORLD, &status); /* Receive a message */
printf("[%d] Received reply message '%d' from process [%d]\n", rank, msg, dst);
} else {
int src = 0;
MPI_Recv(&msg, 1, MPI_INT, src, tag1, MPI_COMM_WORLD, &status); /* Receive a message */
printf("[%d] Received 1st message '%d' from process [%d]\n", rank, msg, src);
msg++;
/* Inject 762.96 Mflops of computation time - Host Jupiter is 76.296Mf per second, so this should amount to 10s */
/* We are in a public file, not internal to SimGrid, so _benched flavour is preferred, as it protects against
* accidental skip */
smpi_execute_flops_benched(762960000);
printf("[%d] After a nap, increment message's value to '%d'\n", rank, msg);
printf("[%d] About to send back message '%d' to process [%d]\n", rank, msg, src);
MPI_Send(&msg, 1, MPI_INT, src, tag2, MPI_COMM_WORLD);
}
MPI_Finalize();
return 0;
}
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