c - For循环在一个循环后退出-MPI

Question

我正在处理一个发送/接收 MPI 程序，由于某种原因，循环只迭代一次然后退出。有谁知道为什么？

代码:

#include <mpi.h>
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[]) {
    int rank;
    int b2, a1;
    MPI_Status status;
    MPI_Init(NULL, NULL);
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);

    for (int j = 0; j < 100; j++) {
        if (rank == 0) {
            a1 = 10;
            MPI_Sendrecv(&a1, 1, MPI_INT, 1, 99,
                    &b2, 1, MPI_INT, 1, 99,
                    MPI_COMM_WORLD, MPI_STATUS_IGNORE);

        } else {
            a1 = 20;
            MPI_Sendrecv(&a1, 1, MPI_INT, 0, 99,
                    &b2, 1, MPI_INT, 0, 99,
                    MPI_COMM_WORLD, MPI_STATUS_IGNORE);
        }
    }

    printf("Process %d: received %d\n", rank, b2);
    MPI_Finalize();

}

输出(这应该重复多次，但这是我得到的全部):

Process 1: received 10
Process 0: received 20

Answer 1

您的 printf() 不在循环中。它只打印一次也就不足为奇了。