I initialized the "rows", but I didn't show that part of code.
The thing is when I declare a, b, c as double two-dimentional arrays, no
error occurrs. But when I use malloc() to allocate memories for a, b and
c, the program doesn't work. Why?
> You don't seem to initialize the "rows" value anywhere.
>
> for(k=0; k<NCB; k++) {
> for(i=0; i<rows; i++) {
> c[i][k] = 0.0;
> for(j=0; j<NCA; j++) {
> c[i][k] = c[i][k] + a[i][j]*b[j][k];
> }
> }
> }
>
> Is "rows" supposed to be NRA?
>
> You're most likely are walking off the end of the allocated memory.
>
> Damien Hocking
>
> Rome wasn’t built in a meeting.
>
>
>
> Yu-Cheng Chou wrote:
>
> >Hi,
> >my matrix multiplication c code looks like this:
> >------------------------------------------------------------------------
---
> >#include <mpi.h>
> >#define NRA 300
> >#define NCA 300
> >#define NCB 300
> > .
> > .
> > .
> >int main(int argc, char *argv[]) {
> > double **a, **b, **c;
> > .
> > .
> > .
> > MPI_Init(&argc, &argv);
> > MPI_Comm_size(MPI_COMM_WORLD, &numtasks);
> > MPI_Comm_rank(MPI_COMM_WORLD, &taskid);
> > .
> > .
> > .
> > a = (double **)malloc(NRA*sizeof(double *));
> > for(i=0; i<NRA; i++) {
> > a[i] = (double *)malloc(NCA*sizeof(double));
> > }
> >
> > b = (double **)malloc(NCA*sizeof(double *));
> > for(i=0; i<NCA; i++) {
> > b[i] = (double *)malloc(NCB*sizeof(double));
> > }
> >
> > c = (double **)malloc(NRA*sizeof(double *));
> > for(i=0; i<NRA; i++) {
> > c[i] = (double *)malloc(NCB*sizeof(double));
> > }
> >
> > if(taskid == MASTER) {
> > // initialize matrix a and matrix b
> > .
> > .
> > .
> > // send matrix data to worker processes
> > .
> > .
> > .
> > }
> > else {
> > // receive matrix data from master process
> > .
> > .
> > .
> > }
> >
> > // for both master and worker processes -- matrix calculation
> > for(k=0; k<NCB; k++) {
> > for(i=0; i<rows; i++) {
> > c[i][k] = 0.0;
> > for(j=0; j<NCA; j++) {
> > c[i][k] = c[i][k] + a[i][j]*b[j][k];
> > }
> > }
> > }
> >
> > if(taskid == MASTER) {
> > // receive results from worker processes
> > .
> > .
> > .
> > }
> > else {
> > // send results to master process
> > .
> > .
> > .
> > }
> >
> > // free all dynamically allocated memories
> > for(i=0; i<NRA; i++) {
> > free(a[i]);
> > }
> > free(a);
> >
> > for(i=0; i<NCA; i++) {
> > free(b[i]);
> > }
> > free(b);
> >
> > for(i=0; i<NRA; i++) {
> > free(c[i]);
> > }
> > free(c);
> >
> > MPI_Finalize();
> >
> > return 0;
> >}
> >------------------------------------------------------------------------
---
> >
> >When I run this program on two machines, error message like this came
out.
> >
> >------------------------------------------------------------------------
---
> >Rank (0, MPI_COMM_WORLD): Call stack within LAM:
> >MPI_Recv: process in local group is dead (rank 0, MPI_COMM_WORLD)
> >Rank (0, MPI_COMM_WORLD): - MPI_Recv()
> >Rank (0, MPI_COMM_WORLD): - main()
> >
> >One of the processes started by mpirun has exited with a nonzero exit
> >code. This typically indicates that the process finished in error.
> >If your process did not finish in error, be sure to include a "return
> >0" or "exit(0)" in your C code before exiting the application.
> >
> >PID 4672 failed on node n1 (169.237.108.13) due to signal 9.
> >------------------------------------------------------------------------
---
> >
> >Any hint for that?
> >
> >
> >
> >
> >_______________________________________________
> >This list is archived at http://www.lam-mpi.org/MailArchives/lam/
> >
> >
> _______________________________________________
> This list is archived at http://www.lam-mpi.org/MailArchives/lam/
>
Best Regards,
Yu-Cheng Chou
Integration Engineering Lab
Mechanical and Aeronautical Engineering
University of California, Davis
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