Код 3.4.4.1.2

#include "mpi.h"

#include <stdio.h>

int main(argc,argv)

int argc;

char *argv[]; {

int numtasks, rank, next, prev, buf[2], tag1=1, tag2=2;

MPI_Request reqs[4];

MPI_Status stats[4];

MPI_Init(&argc,&argv);

MPI_Comm_size(MPI_COMM_WORLD, &numtasks);

MPI_Comm_rank(MPI_COMM_WORLD, &rank);

prev = rank-1;

next = rank+1;

if (rank == 0) prev = numtasks - 1;

if (rank == (numtasks - 1)) next = 0;

MPI_Irecv(&buf[0], 1, MPI_INT, prev, tag1, MPI_COMM_WORLD, &reqs[0]);

MPI_Irecv(&buf[1], 1, MPI_INT, next, tag2, MPI_COMM_WORLD, &reqs[1]);

MPI_Isend(&rank, 1, MPI_INT, prev, tag2, MPI_COMM_WORLD, &reqs[2]);

MPI_Isend(&rank, 1, MPI_INT, next, tag1, MPI_COMM_WORLD, &reqs[3]);

{ do some work }

MPI_Waitall(4, reqs, stats);

MPI_Finalize();

}

Коллективные взаимодействия

Types of Collective Operations:

• Data Movement - broadcast, scatter/gather, all to all.
• Collective Computation (reductions) - one member of the group collects data from the other members and performs an operation (min, max, add, multiply, etc.) on that data.
• Synchronization - processes wait until all members of the group have reached the synchronization point.

3.4.5. 1. Коллективные (радиовещательные) обмены данными (Data Movement)