Question

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

int main(int argc, char *argv[])
{
    int myid, numprocs, number_of_completed_operation;

    char message = 'a';


    MPI_Init(&argc, &argv);
    MPI_Comm_size(MPI_COMM_WORLD, &numprocs);
    MPI_Comm_rank(MPI_COMM_WORLD, &myid);

    MPI_Request* requests = (MPI_Request*)malloc((numprocs - 1)*sizeof(MPI_Request));
    MPI_Status* statuses = (MPI_Status*)malloc(sizeof(MPI_Status)*(numprocs - 1));
    int* indices = (int *)malloc((numprocs - 1)*sizeof(int));
    char* buf = (char *)malloc((numprocs - 1)*sizeof(char));

    if (myid != numprocs - 1)
    {//worker

        printf("***this is sender %d\n", myid);
        MPI_Send(&message, 1, MPI_CHAR, numprocs - 1, 110, MPI_COMM_WORLD);
        printf("*.*sender %d is done\n", myid);



    }
    else if (myid == numprocs - 1)
    {
        //master
        int number_of_left_messages = numprocs - 1;//有numprocs-1个信息到来
        int i;
        for (i = 0; i < numprocs - 1; i++)
        {
            MPI_Irecv(&buf+i, 1, MPI_CHAR,i, 110, MPI_COMM_WORLD, &requests[i]);
        }

        MPI_Waitsome(numprocs - 1, requests, &number_of_completed_operation, indices, statuses);


        number_of_left_messages = number_of_left_messages - number_of_completed_operation;
        printf("number of completed operation is %d\n", number_of_left_messages);
        printf("left message amount is %d\n", number_of_left_messages);

        int j;
        for (j = 0; j <numprocs - 1; j++)
        {
            printf("-------------\n");
            printf("index is %d\n",indices[j]);
            printf("source is %d\n", statuses[j].MPI_SOURCE);
            //printf("good\n");
            printf("--------====\n");

        }

        while (number_of_left_messages > 0)
        {
            MPI_Waitsome(numprocs - 1, requests, &number_of_completed_operation, indices, statuses);

            printf("number of completed operation is %d\n", number_of_completed_operation);
            for (j = 0; j <numprocs - 1; j++)
            {
                printf("-------------\n");
                printf("index is %d\n", indices[j]);
                printf("source is %d\n", statuses[j].MPI_SOURCE);
                printf("--------====\n");
            }
            number_of_left_messages = number_of_left_messages - number_of_completed_operation;
            printf("left message amount is %d\n", number_of_left_messages);

逻辑很简单，我将最后的进程设置为主进程，所有其他进程都是工作进程，工作者向主进程发送消息，主进程使用waitsome函数进行接收。当我将进程数设置为4或更大时，系统显示错误如下：

[soit-mpi-pro-1:12197] *** An error occurred in MPI_Waitsome
[soit-mpi-pro-1:12197] *** reported by process [140533176729601,140531329925123]
[soit-mpi-pro-1:12197] *** on communicator MPI_COMM_WORLD
[soit-mpi-pro-1:12197] *** MPI_ERR_REQUEST: invalid request
[soit-mpi-pro-1:12197] *** MPI_ERRORS_ARE_FATAL (processes in this communicator will now abort,
[soit-mpi-pro-1:12197] ***    and potentially your MPI job)

Answer 1

看起来您对MPI_Irecv的调用可能是个问题。删除&之前的额外buf（你有一个双指针而不是一个指针）。

MPI_Irecv(buf+i, 1, MPI_CHAR,i, 110, MPI_COMM_WORLD, &requests[i]);

当我解决这个问题时，添加结束括号并调用MPI_Finalize()，并删除一堆额外的输出，我在运行程序时没有任何问题：

$ mpiexec -n 8 ./a.out
***this is sender 3
*.*sender 3 is done
***this is sender 4
*.*sender 4 is done
***this is sender 5
*.*sender 5 is done
***this is sender 6
*.*sender 6 is done
***this is sender 0
*.*sender 0 is done
***this is sender 1
*.*sender 1 is done
***this is sender 2
*.*sender 2 is done
number of completed operation is 1
left message amount is 6
number of completed operation is 1
left message amount is 5
number of completed operation is 1
left message amount is 4
number of completed operation is 1
left message amount is 3
number of completed operation is 1
left message amount is 2
number of completed operation is 1
left message amount is 1
number of completed operation is 1
left message amount is 0

我不知道它是否得到了正确的答案，但这是一个不同的问题。

Answer 2

您正在传递MPI_Irecv指针buf本身的地址加上偏移而不是其值。收到消息后，它会覆盖一个或多个附近堆栈变量的最后一个字节（在x86 / x64之类的小端系统上），这取决于堆栈布局，可能包括requests和{{ 1}}。因此statuses接收的指针不指向请求数组的开头，而是指向它之前，之后或其中间的某个位置，因此某些请求句柄无效且{{1}抱怨。在大端系统上，这会覆盖地址的最高字节，而且会导致无效的地址和分段错误。

使用MPI_Waitsome（根据Wesley Bland的答案）或使用MPI_Waitsome。我通常会发现个人品味是否使用第二种形式的第一种。

MPI_Waitsome发生错误

2 个答案: