C并行编程，信号：分段故障：（11）11信号代码：地址未映射（1）

我现在正在使用MPI做一个简单的并行编程。我在编译时没有遇到错误，但在运行时遇到了一些我无法理解的错误。请帮忙！谢谢你们！ 源代码如下：

#include <stdio.h>
#include <stdlib.h>
#include "mpi.h"
#include "matrix.h"
#define MIN(X,Y) (((X) < (Y)) ? (X) : (Y)) //IMPORTANT!!

int master = 0;
int numsent, i;
int nrows, ncols;
double *A, *x, *b, *buffer;
int rowidx;
int sender;
double ans;


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

    MPI_Init(&argc, &argv);
    MPI_Comm_size(MPI_COMM_WORLD, &nproc);
    MPI_Comm_rank(MPI_COMM_WORLD, &myid);
    /* CODING */

    MPI_Status stat; // IMPORTANT!!

    //master_stage1: master obtain the matrix A and vector X
    if(myid == master)
    {
        printf("What is the number of rows of matrix A:\n");
        scanf("%d", &nrows);
        printf("what is the number of columns of matrix A:\n");
        scanf("%d", &ncols);

        //printf("nrows = %d, ncols = %d\n", nrows, ncols);//text



        A = (double*)malloc(nrows*ncols*sizeof(double));
        b = (double*)malloc(nrows*sizeof(double));
        ObtainMatrixAndVector(nrows, ncols, A, x, b);
    }

    //master_stage2:bcast x, ncols, nrows, and p2p sent rows of A
    MPI_Bcast(&ncols, 1, MPI_INT, master, MPI_COMM_WORLD);
    MPI_Bcast(&nrows, 1, MPI_INT, master, MPI_COMM_WORLD);

    x = (double*)malloc(ncols*sizeof(double));
    MPI_Bcast(x, ncols, MPI_DOUBLE, master, MPI_COMM_WORLD);

    if(myid == master)
    {
        numsent = 0;
        for(i = 1; i <= MIN(nrows, nproc - 1); i++)
        {
            MPI_Send(&A[(i - 1)*ncols], ncols, MPI_DOUBLE, i, i, MPI_COMM_WORLD);
            numsent++;
        }

        //master_stage3: receiving
        for(i = 0; i <= nrows; i++)
        {
            MPI_Recv(&ans, 1, MPI_DOUBLE, MPI_ANY_SOURCE, MPI_ANY_TAG, MPI_COMM_WORLD, &stat);
            sender = stat.MPI_SOURCE;
            rowidx = stat.MPI_TAG;
            b[rowidx-1] = ans;

            if(numsent < nrows)
            {
                MPI_Send(&A[numsent*ncols], ncols, MPI_DOUBLE, sender, numsent+1, MPI_COMM_WORLD);
                numsent++;
            }
            else
                MPI_Send(buffer, ncols, MPI_DOUBLE, sender, 0, MPI_COMM_WORLD);
        }
    }

    //Jobs Done by workers
    buffer = (double*)malloc(ncols*sizeof(double));
    while(1)
    {
        if(myid > nrows)
            break;
        else
        {
            MPI_Recv(buffer, ncols, MPI_DOUBLE, MPI_ANY_SOURCE, MPI_ANY_TAG, MPI_COMM_WORLD, &stat);

            rowidx = stat.MPI_TAG;
            if(rowidx == 0)
                break;
            ans = 0.0;
            for(i = 0; i < ncols; i++)
                ans += buffer[i] * x[i];
            MPI_Send(&ans, 1, MPI_DOUBLE, master, rowidx, MPI_COMM_WORLD);

        }
    }
    if(myid == master)
    {
        for(i = 0; i < nrows; i++)
            printf("%f\n", b[i]);
    } 

    /* CODING */
    MPI_Finalize();
}

错误：

[Nicks-MAC:02138] *** Process received signal ***
[Nicks-MAC:02138] Signal: Segmentation fault: 11 (11)
[Nicks-MAC:02138] Signal code: Address not mapped (1)
[Nicks-MAC:02138] Failing at address: 0x0
[Nicks-MAC:02138] [ 0] 0   libsystem_platform.dylib            0x00007fffbf27bbba _sigtramp + 26
[Nicks-MAC:02138] [ 1] 0   a.out                               0x0000000106daf0eb x + 4147
[Nicks-MAC:02138] [ 2] 0   a.out                               0x0000000106dad7a1 main + 321
[Nicks-MAC:02138] [ 3] 0   libdyld.dylib                       0x00007fffbf06e255 start + 1
[Nicks-MAC:02138] *** End of error message ***
--------------------------------------------------------------------------
mpirun noticed that process rank 0 with PID 0 on node Nicks-MAC exited on signal 11 (Segmentation fault: 11).
--------------------------------------------------------------------------

---

非常感谢大家

我想我看到了错误：

      ObtainMatrixAndVector(nrows, ncols, A, x, b);
}

//master_stage2:bcast x, ncols, nrows, and p2p sent rows of A
MPI_Bcast(&ncols, 1, MPI_INT, master, MPI_COMM_WORLD);
MPI_Bcast(&nrows, 1, MPI_INT, master, MPI_COMM_WORLD);

x = (double*)malloc(ncols*sizeof(double));

在给数组分配内存之前，使用指向数组x的指针

试试这个：

A = (double*)malloc(nrows*ncols*sizeof(double));
b = (double*)malloc(nrows*sizeof(double));
x = (double*)malloc(ncols*sizeof(double));
ObtainMatrixAndVector(nrows, ncols, A, x, b);

---

您的代码中有许多错误

• 在调用ActainMatrix和Vector之前，无法在主机上分配

  x

  。在主机上分配之前一定要先分配。但是，您还必须使

  x

  的其他分配仅适用于非主机

• 同样，您也无法在主主节之前分配

  缓冲区。将该分配移到该部分之前
  

• 您无条件地执行工作者代码。主机不应执行工作代码

---

• 你在这里一点一点地离开

  （i＝0；如果问题是关于C，为什么是C++标签？不要垃圾邮件标签！抱歉，我只需点击建议标签。现在我将删除C++标签。谢谢你的帮助亚历克斯。我尝试了你所说的但是它得到更多的错误。我是MPI的初学者。我现在迷路了。非常感谢。我会尝试你所提到的并让你知道结果。我建议。你编辑了问题，添加了你修复了我提到的问题的版本。但是保留原始版本。
        ObtainMatrixAndVector(nrows, ncols, A, x, b);
  }
  
  //master_stage2:bcast x, ncols, nrows, and p2p sent rows of A
  MPI_Bcast(&ncols, 1, MPI_INT, master, MPI_COMM_WORLD);
  MPI_Bcast(&nrows, 1, MPI_INT, master, MPI_COMM_WORLD);
  
  x = (double*)malloc(ncols*sizeof(double));
  
  A = (double*)malloc(nrows*ncols*sizeof(double));
  b = (double*)malloc(nrows*sizeof(double));
  x = (double*)malloc(ncols*sizeof(double));
  ObtainMatrixAndVector(nrows, ncols, A, x, b);