I'm guessing that you're trying to allocate too much memory on the
stack -- multiple arrays on the order of double[3000][2000] are
probably going to cause the OS to kill the program before it starts
because it can't allocate that much memory on the stack. Hence, I'm
guessing that this is not an MPI problem.
Use malloc to allocate your arrays instead (google around to see how
to properly allocate 2D arrays with malloc).
On Dec 16, 2005, at 5:55 PM, Yu-Cheng Chou wrote:
> hi,
> I have a matrix multiplication program to be run on multiple machines.
> The program works fine with small size matrices, but doesn't work
> with large size matrices.
> Besides, the working size of matrix is much smaller for windows
> than the one for linux.
>
> Can anyone tell me the possible reason that causes this error?
>
> Below shows my program C source code.
>
> #include <mpi.h>
> #include <stdio.h>
> #define NRA 3000 // number of rows in matrix A
> #define NCA 2000 // number of columns in matrix A
> #define NCB 400 // number of columns in matrix B
> #define MASTER 0 // taskid of first task
> #define FROM_MASTER 1 // setting a message type
> #define FROM_WORKER 2 // setting a message type
> int main(int argc, char *argv[]) {
> int numtasks, // number of tasks
> taskid, // task identifier
> source, // task id of message source
> dest, // task id of message destination
> mtype, // message type
> rows, // rows of matrix A sent to
> each worker
> averow, extra, offset, // used to determine rows sent
> to each worker
> i, j, k; // misc
> double a[NRA][NCA], // matrix A to be multiplied
> b[NCA][NCB], // matrix B to be multiplied
> c[NRA][NCB]; // result matrix C
> MPI_Status status;
> printf("debug_1\n"); // the execution did not come to
> this point
> MPI_Init(&argc, &argv);
> MPI_Comm_size(MPI_COMM_WORLD, &numtasks);
> MPI_Comm_rank(MPI_COMM_WORLD, &taskid);
> if(taskid == MASTER) {
> printf("Number of worker tasks = %d\n", numtasks-1);
> // initialize matrix a and matrix b
> for(i=0; i<NRA; i++) {
> for(j=0; j<NCA; j++) {
> a[i][j] = i+j;
> }
> }
> for(i=0; i<NCA; i++) {
> for(j=0; j<NCB; j++) {
> b[i][j] = i*j;
> }
> }
> // send matrix data to worker processes
> averow = NRA/(numtasks-1);
> extra = NRA%(numtasks-1);
> offset = 0;
> mtype = FROM_MASTER;
> for(dest=1; dest<numtasks; dest++) {
> rows = (dest <= extra) ? averow+1 : averow;
> printf(" sending %d rows to task %d\n", rows, dest);
> MPI_Send(&offset, 1, MPI_INT, dest, mtype,
> MPI_COMM_WORLD);
> MPI_Send(&rows, 1, MPI_INT, dest, mtype, MPI_COMM_WORLD);
> MPI_Send(&a[offset][0], rows*NCA, MPI_DOUBLE, dest,
> mtype, MPI_COMM_WORLD);
> MPI_Send(&b, NCA*NCB, MPI_DOUBLE, dest, mtype,
> MPI_COMM_WORLD);
> offset = offset + rows;
> }
> }
> else {
> // receive matrix data from master process
> mtype = FROM_MASTER;
> MPI_Recv(&offset, 1, MPI_I! NT, MASTER, mtype,
> MPI_COMM_WORLD, &status);
> MPI_Recv(&rows, 1, MPI_INT, MASTER, mtype, MPI_COMM_WORLD,
> &status);
> MPI_Recv(&a, rows*NCA, MPI_DOUBLE, MASTER, mtype,
> MPI_COMM_WORLD, &status);
> MPI_Recv(&b, NCA*NCB, MPI_DOUBLE, MASTER, mtype,
> MPI_COMM_WORLD, &status);
> }
> if(taskid == MASTER) {
> // receive results from worker processes
> mtype = FROM_WORKER;
> for(source=1; source<numtasks; source++) {
> MPI_Recv(&offset, 1, MPI_INT, source, mtype,
> MPI_COMM_WORLD, &status);
> MPI_Recv(&rows! , 1, MPI_INT, source, mtype,
> MPI_COMM_WORLD, &status);
> MPI_Recv(&c[offset][0], rows*NCB, MPI_DOUBLE, source,
> mtype, MPI_COMM_WORLD, &status);
> }
> }
> else {
> // 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];
> }
> }
> }
> // send results to master process
> mtype = FROM_WORKER;
> MPI_Send(&offset, 1, MPI_INT, MASTER, mtype, MPI_COMM_WORLD);
> MPI_Send(&rows, 1, MPI_INT, MASTER, mtype, MPI_COMM_WORLD);
> MPI_Send(&c, rows*NCB, MPI_DOUBLE, MASTER, mtype,
> MPI_COMM_WORLD);
> }
> if(taskid == MASTER) {
> printf("Here is the result matrix\n\n");
> /*
> for(i=0; ! i<NRA; i++) {
> for(j=0; j<NCB; j++) {
> printf("%6.2f ", c[i][j]);
> }
> printf("\n");
> }
> */
> }
> MPI_Finalize();
> return 0;
> }
>
> _______________________________________________
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--
{+} Jeff Squyres
{+} The Open MPI Project
{+} http://www.open-mpi.org/
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