1 /* Copyright (c) 2018-2022. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
10 #define N (1024 * 1024 * 1)
12 int main(int argc, char* argv[])
15 struct timeval start, end;
19 MPI_Init(&argc, &argv);
21 MPI_Comm_rank(MPI_COMM_WORLD, &rank);
22 MPI_Comm_size(MPI_COMM_WORLD, &size);
23 MPI_Get_processor_name(hostname, &hostname_len);
25 // Allocate a 1 MiB buffer
26 char* buffer = malloc(sizeof(char) * N);
28 // Communicate along the ring
30 gettimeofday(&start, NULL);
31 printf("Rank %d (running on '%s'): sending the message rank %d\n", rank, hostname, 1);
32 MPI_Send(buffer, N, MPI_BYTE, 1, 1, MPI_COMM_WORLD);
33 MPI_Recv(buffer, N, MPI_BYTE, size - 1, 1, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
34 printf("Rank %d (running on '%s'): received the message from rank %d\n", rank, hostname, size - 1);
35 gettimeofday(&end, NULL);
36 printf("%f\n", (end.tv_sec * 1000000.0 + end.tv_usec - start.tv_sec * 1000000.0 - start.tv_usec) / 1000000.0);
39 MPI_Recv(buffer, N, MPI_BYTE, rank - 1, 1, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
40 printf("Rank %d (running on '%s'): receive the message and sending it to rank %d\n", rank, hostname,
42 MPI_Send(buffer, N, MPI_BYTE, (rank + 1) % size, 1, MPI_COMM_WORLD);