c - MPI，我更改了一个非常简单的程序以使用 INT 而不是 CHAR 作为消息缓冲区的数据类型，但现在它失败了，这是为什么？

Question

我拿了the MPI example on the wikipedia page并将其修改为使用整数而不是字符。

结果是:

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

int main(int argc, char **argv)
{
    int buf[4];
    int my_rank, num_procs;

    /* Initialize the infrastructure necessary for communication */
    MPI_Init(&argc, &argv);

    /* Identify this process */
    MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);

    /* Find out how many total processes are active */
    MPI_Comm_size(MPI_COMM_WORLD, &num_procs);
    int test[4] = {0, 1, 2};

    /* Until this point, all programs have been doing exactly the same.
       Here, we check the rank to distinguish the roles of the programs */
    if (my_rank == 0) {
        int other_rank;
        printf("We have %i processes.\n", num_procs);

        /* Send messages to all other processes */
        for (other_rank = 1; other_rank < num_procs; other_rank++)
        {
            memcpy(buf, test, 4 * sizeof(int));
            MPI_Send(buf, sizeof(buf), MPI_INT, other_rank,
                     0, MPI_COMM_WORLD);
        }

        /* Receive messages from all other process */
        for (other_rank = 1; other_rank < num_procs; other_rank++)
        {
            MPI_Recv(buf, sizeof(buf), MPI_INT, other_rank,
                     0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
            printf("%d\n", buf[other_rank]);
        }

    } else {

        /* Receive message from process #0 */
        MPI_Recv(buf, sizeof(buf), MPI_INT, 0,
                 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
        memcpy(buf, test, 4 * sizeof(int));
        MPI_Send(buf, sizeof(buf), MPI_INT, 0,
                 0, MPI_COMM_WORLD);

    }

    /* Tear down the communication infrastructure */
    MPI_Finalize();
    return 0;
}

显然代码应该做同样的事情，因为错误传递了一个整数数组而不是字符串，实际上我收到了这个错误:

YOUR APPLICATION TERMINATED WITH THE EXIT STRING: Illegal instruction
(signal 4) This typically refers to a problem with your application.
Please see the FAQ page for debugging suggestions

我这里有什么地方做错了吗？

我正在使用这个简单的命令进行编译和执行:

mpicc example.c && mpiexec -n 4 ./a.out

Answer 1

回顾 int MPI_Send(const void *buf, int count, MPI_Datatype datatype, int dest, int tag, MPI_Comm comm) 等。

count 是发送缓冲区中元素的数量，而不是它的大小。

代码应该是:

// MPI_Send(buf, sizeof(buf), MPI_INT, other_rank, 0, MPI_COMM_WORLD);`
MPI_Send(buf, sizeof buf /sizeof buf[0], MPI_INT, other_rank, 0, MPI_COMM_WORLD);`

检查 MPI_Recv(); 和所有类似的调用。 @Gilles Gouaillardet