[英]Matrix Vector multiplication in MPI and C
i'm trying to multiply a square matrix by a vector using MPI and C. I must use MPI_Allgather to send all the parts of the matrix to all the processes. 我正在尝试使用MPI和C将方形矩阵乘以向量。我必须使用MPI_Allgather将矩阵的所有部分发送到所有进程。 This is what i have so far
这就是我到目前为止所拥有的
#include "mpi.h"
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <string.h>
#include <time.h>
#define DIM 500
int main(int argc, char *argv[])
{
int i, j, n;
int nlocal; /* Number of locally stored rows of A */
double *fb;
double a[DIM*DIM], b[DIM], x[DIM]; /* Will point to a buffer that stores the entire vector b */
int npes, myrank;
MPI_Status status;
MPI_Init(&argc,&argv);
/* Get information about the communicator */
MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
MPI_Comm_size(MPI_COMM_WORLD, &npes);
/* Allocate the memory that will store the entire vector b */
fb = (double*)malloc(n*sizeof(double));
nlocal = n/npes;
/* Gather the entire vector b on each processor using MPI's ALLGATHER operation */
MPI_Allgather(b, nlocal, MPI_DOUBLE, fb, nlocal, MPI_DOUBLE, MPI_COMM_WORLD);
/* Perform the matrix-vector multiplication involving the locally stored submatrix */
for (i=0; i<nlocal; i++) {
x[i] = 0.0;
for (j=0; j<n; j++)
x[i] += a[i*n+j]*fb[j];
}
free(fb);
MPI_Finalize();
}//end main
OK Now it works! 好现在它有效! It compiles but then i get an mpi allgather internal error!
它编译但然后我得到一个mpi allgather内部错误! I got this also with other solution i tried.
我也尝试了其他解决方案。
Fatal error in MPI_Allgather: Internal MPI error!, error stack:
MPI_Allgather(961).......: MPI_Allgather(sbuf=0xa1828, scount=407275437, MPI_DOU BLE, rbuf=0xf61d0008, rcount=407275437, MPI_DOUBLE, MPI_COMM_WORLD) failed
MPIR_Allgather_impl(807).:
MPIR_Allgather(766)......:
MPIR_Allgather_intra(560):
MPIR_Localcopy(357)......: memcpy arguments alias each other, dst=0xb8513d70 src =0xa1828 len=-1036763800
Fatal error in MPI_Allgather: Internal MPI error!, error stack:
MPI_Allgather(961).......: MPI_Allgather(sbuf=0xa1828, scount=407275437, MPI_DOU BLE, rbuf=0xf61d0008, rcount=407275437, MPI_DOUBLE, MPI_COMM_WORLD) failed
MPIR_Allgather_impl(807).:
MPIR_Allgather(766)......:
MPIR_Allgather_intra(560):
MPIR_Localcopy(357)......: memcpy arguments alias each other, dst=0x3cb9b840 src =0xa1828 len=-1036763800
Fatal error in MPI_Allgather: Internal MPI error!, error stack:
MPI_Allgather(961).......: MPI_Allgather(sbuf=0xa1828, scount=407275437, MPI_DOU BLE, rbuf=0xf61d0008, rcount=407275437, MPI_DOUBLE, MPI_COMM_WORLD) failed
MPIR_Allgather_impl(807).:
MPIR_Allgather(766)......:
MPIR_Allgather_intra(560):
MPIR_Localcopy(357)......: memcpy arguments alias each other, dst=0x7a857ad8 src =0xa1828 len=-1036763800
Can anyone help me? 谁能帮我?
Any way you are accessing the two dimensional array using one dimension(row or column major), you can allocate two dimensional array as a[DIM*DIM]
instead of a[DIM][DIM]
and access this in a linear fashion. 无论您使用一个维度(行或列主要)访问二维数组,您都可以将二维数组分配为
a[DIM*DIM]
而不是a[DIM][DIM]
并以线性方式访问它。 This solution is working for me. 这个解决方案对我有用。
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