Hi, The following matrix multiplication code does not execute in my machine for MATRIX_ORDER greater than 400 or so, and I've got plenty of memory. Is there anything I need to tweak in MPI.h for this to work?? Thanks for any help. Alejandro #include <stdio.h> #include "mpi.h" /* for the Wtime() function only */ #define MATRIX_ORDER 400 typedef float MATRIX_T[MATRIX_ORDER][MATRIX_ORDER]; void serial_matrix_mult(MATRIX_T A, MATRIX_T B, MATRIX_T C, int n); int main(int argc, char* argv[]) { MATRIX_T A; MATRIX_T B; MATRIX_T C; int i, j; double start, finish; int p, my_rank; MPI_Init(&argc,&argv); MPI_Comm_size(MPI_COMM_WORLD, &p); MPI_Comm_rank(MPI_COMM_WORLD, &my_rank); for (i = 0; i < MATRIX_ORDER; i++) /* initialize matrices */ for (j = 0; j < MATRIX_ORDER; j++) /* to an arbitrary value */ { A[i][j] = 5; B[i][j] = 5; } start = MPI_Wtime(); serial_matrix_mult(A, B, C, MATRIX_ORDER); finish = MPI_Wtime(); printf("Elapsed time in seconds is %e\n", finish - start ); MPI_Finalize(); }