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/*
* Copyright (C) 2010. See COPYRIGHT in top-level directory.
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdint.h>
#include <mpi.h>
#define MAX_SIZE (128*1024)
#define NUM_ROUNDS 10000
#define PROBE_PROGRESS
int main(int argc, char **argv) {
int me, nproc, target;
int msg_length, round, i;
double t_start, t_stop;
uint8_t *snd_buf; // Send buffer (byte array)
uint8_t *rcv_buf; // Receive buffer (byte array)
MPI_Win window;
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &me);
MPI_Comm_size(MPI_COMM_WORLD, &nproc);
if (nproc < 2) {
if (me == 0) printf("This benchmark should be run on at least two processes\n");
MPI_Abort(MPI_COMM_WORLD, 1);
}
if (me == 0)
printf("MPI-2 passive ping-pong latency test, performing %d rounds at each xfer size.\n", NUM_ROUNDS);
MPI_Alloc_mem(MAX_SIZE, MPI_INFO_NULL, &rcv_buf);
MPI_Alloc_mem(MAX_SIZE, MPI_INFO_NULL, &snd_buf);
MPI_Win_create(rcv_buf, MAX_SIZE, 1, MPI_INFO_NULL, MPI_COMM_WORLD, &window);
for (i = 0; i < MAX_SIZE; i++) {
snd_buf[i] = 1;
}
for (target = 1; target < nproc; target++) {
if (me == 0) printf("\n========== Process pair: %d and %d ==========\n\n", 0, target);
for (msg_length = 1; msg_length <= MAX_SIZE; msg_length *= 2) {
MPI_Barrier(MPI_COMM_WORLD);
t_start = MPI_Wtime();
if (me == 0 || me == target) {
// Perform NUM_ROUNDS ping-pongs
for (round = 0; round < NUM_ROUNDS*2; round++) {
int my_target = me == 0 ? target : 0;
// I am the sender
if ((round % 2 == 0 && me == 0) || (round % 2 != 0 && me != 0)) {
// Clear start and end markers for next round
MPI_Win_lock(MPI_LOCK_EXCLUSIVE, me, 0, window);
rcv_buf[0] = 0;
rcv_buf[msg_length-1] = 0;
MPI_Win_unlock(me, window);
MPI_Win_lock(MPI_LOCK_EXCLUSIVE, my_target, 0, window);
MPI_Put(snd_buf, msg_length, MPI_BYTE, my_target, 0, msg_length, MPI_BYTE, window);
MPI_Win_unlock(my_target, window);
}
// I am the receiver: Poll start and end markers
else {
uint8_t val;
do {
#ifdef PROBE_PROGRESS
/* Needed for progress in many MPI implementations.. */
MPI_Iprobe(0, 0, MPI_COMM_WORLD, (void*) &val, MPI_STATUS_IGNORE);
#endif
MPI_Win_lock(MPI_LOCK_EXCLUSIVE, me, 0, window);
val = ((volatile uint8_t*)rcv_buf)[0];
MPI_Win_unlock(me, window);
} while (val == 0);
do {
#ifdef PROBE_PROGRESS
MPI_Iprobe(0, 0, MPI_COMM_WORLD, (void*) &val, MPI_STATUS_IGNORE);
#endif
MPI_Win_lock(MPI_LOCK_EXCLUSIVE, me, 0, window);
val = ((volatile uint8_t*)rcv_buf)[msg_length-1];
MPI_Win_unlock(me, window);
} while (val == 0);
}
}
}
MPI_Barrier(MPI_COMM_WORLD);
t_stop = MPI_Wtime();
if (me == 0)
printf("%8d bytes \t %12.8f us\n", msg_length, (t_stop-t_start)/NUM_ROUNDS*1.0e6);
}
MPI_Barrier(MPI_COMM_WORLD);
}
MPI_Win_free(&window);
MPI_Free_mem(snd_buf);
MPI_Free_mem(rcv_buf);
MPI_Finalize();
return 0;
}
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