c - MPI 错误 : expected expression before ‘,’ token

Question

我在使用 MPI_Send 时遇到一个奇怪的错误——我在尝试发送二维数组(矩阵)的一部分时收到此错误:“MPI_matrixMultiplication.c:68:99:错误:'，'之前的预期表达式 token ”。 如果矩阵是 MPI_Send(&a[beginPosition][0],... ); ，则特定行是我尝试发送一部分的行；(如您所见，我已经评论了与矩阵相关的其他发送和接收。

    /////////////////////////////////////////////////////////
// multiplication of 2 matrices, parallelized using MPI //
/////////////////////////////////////////////////////////
#include <stdio.h>
#include <mpi.h>

// must use #define here, and not simply int blahblahblah, because "c" doesnt like ints for array dimension :(
#define matrixARowSize  3       // size of the row for matrix A
#define matrixAColumnSize  3    // size of the column for matrix A
#define matrixBRowSize  3       // size of the row for matrix B
#define matrixBColumnSize  3    // size of the column for matrix B

// tags used for sending/receiving data:
#define LOWER_BOUND 1   // first line to be processed
#define UPPER_BOUND 2   // last line to be processed
#define DATA        // data to be processed

int a[matrixARowSize][matrixAColumnSize];       // matrix a
int b[matrixBRowSize][matrixBColumnSize];       // matrix b
int c[matrixARowSize][matrixBColumnSize];       // matrix c
int main()
{
    int currentProcess; // current process
    int worldSize;      // world size
    int i, j, k;        // iterators
    int rowsComputedPerProcess;     // how many rows of the first matrix should be computed in each process
    int numberOfSlaveProcesses;     // the number of slave processes
    int processesUsed;      //how many processes of the available ones are actually used

    MPI_Init(NULL, NULL);       // MPI_Init()
    MPI_Comm_size(MPI_COMM_WORLD, &worldSize);      // get the world size
    MPI_Comm_rank(MPI_COMM_WORLD, &currentProcess);     // get current process

    numberOfSlaveProcesses = worldSize - 1;     // 0 is the master, rest are slaves
    rowsComputedPerProcess = worldSize > matrixARowSize ? 1 : (matrixARowSize/numberOfSlaveProcesses);
    processesUsed = worldSize > matrixARowSize ? matrixARowSize : numberOfSlaveProcesses;

    /*
     * in the first process (the father);
     * initialize the 2 matrices, then start splitting the data to the slave processes
     */ 
    if (!currentProcess)        // in father process
    {
        printf("rows per process: %d\n", rowsComputedPerProcess);
        printf("nr of processes used: %d\n", processesUsed);
        // init matrix A
        for(i = 0; i < matrixARowSize; ++i)
            for(j = 0; j < matrixAColumnSize; ++j){
                a[i][j] = i + j + 1;
                // printf("%d\n", a[i][j]);
                // printf("%d\n", *(a[i] + j));
            }

        // init matrix B
        for(i = 0; i < matrixBRowSize; ++i)
            for(j = 0; j < matrixBColumnSize; ++j)
                b[i][j] = i + j + 1;

        // start sending data to the slaves for them to work >:)
        int beginPosition;  // auxiliary values used for sending the offsets to slaves
        int endPosition;
        for(i = 1; i < processesUsed; ++i)      // the last process is dealt with separately
        {
            beginPosition = (i - 1)*rowsComputedPerProcess;
            endPosition = i*rowsComputedPerProcess;
            MPI_Send(&beginPosition, 1, MPI_INT, i, LOWER_BOUND, MPI_COMM_WORLD);
            MPI_Send(&endPosition, 1, MPI_INT, i, UPPER_BOUND, MPI_COMM_WORLD);
            MPI_Send(&a[beginPosition][0], ((endPosition - beginPosition)*matrixARowSize), MPI_INT, i, DATA, MPI_COMM_WORLD);
            // MPI_Send(a[beginPosition], (endPosition - beginPosition)*matrixARowSize, MPI_INT, i, DATA, MPI_COMM_WORLD);
            // for(j = beginPosition; j < endPosition; ++j)
            //  for (k = 0; k < matrixAColumnSize; ++k)
            //  {
            //      printf("%d ", *(a[j] + k));

            //  }
            // printf("\n");
            // printf("beg: %d, end: %d\n", beginPosition, endPosition);
            // printf(" data #%d\n", (endPosition - beginPosition)*matrixARowSize);
        }

        // deal with last process
        beginPosition = (i - 1)*rowsComputedPerProcess;
        endPosition = matrixARowSize;
        MPI_Send(&beginPosition, 1, MPI_INT, i, LOWER_BOUND, MPI_COMM_WORLD);
        MPI_Send(&endPosition, 1, MPI_INT, i, UPPER_BOUND, MPI_COMM_WORLD);
        // MPI_Send(a[beginPosition], (endPosition - beginPosition)*matrixARowSize, MPI_INT, i, DATA, MPI_COMM_WORLD);
        // printf("beg: %d, end: %d\n", beginPosition, endPosition);
        // printf(" data #%d\n", (endPosition - beginPosition)*matrixARowSize);
    }
    else {      // if this is a slave (rank > 0)
        int beginPosition;  // auxiliary values used for sending the offsets to slaves
        int endPosition;

        MPI_Recv(&beginPosition, 1, MPI_INT, 0, LOWER_BOUND, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
        MPI_Recv(&endPosition, 1, MPI_INT, 0, UPPER_BOUND, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
        // MPI_Recv(a[beginPosition], (endPosition - beginPosition)*matrixARowSize, 0, DATA, MPI_COMM_WORLD, MPI_STATUS_IGNORE);

        for(i  = beginPosition; i < endPosition; ++i) {
            for (j = 0; j < matrixAColumnSize; ++j)
                printf("(# %d, i=%d, j=%d: %d ", currentProcess, i, j, a[i][j]);
            // printf("\n");
        }

    }


    MPI_Finalize();
    return 0;       // bye-bye
}

Answer 1

您的DATA 常量为空。

#define DATA        // data to be processed

所以你想做的是:

MPI_Send(&a[beginPosition][0], ((endPosition - beginPosition)*matrixARowSize), MPI_INT, i, , MPI_COMM_WORLD);

这在逻辑上会生成一个 expected expression before ',' token 错误。