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 /****************************************************************************** * OpenMP Example - Matrix-vector multiplication - C/C++ Version * FILE: omp_matvec.c * DESCRIPTION: * This example multiplies all row i elements of matrix A with vector * element b(i) and stores the summed products in vector c(i). A total is * maintained for the entire matrix. Performed by using the OpenMP loop * work-sharing construct. The update of the shared global total is * serialized by using the OpenMP critical directive. * SOURCE: Blaise Barney 5/99 * LAST REVISED: ******************************************************************************/ #include #include #define SIZE 10 int main () { float A[SIZE][SIZE], b[SIZE], c[SIZE], total; int i, j, tid; /* Initializations */ total = 0.0; for (i=0; i < SIZE; i++) { for (j=0; j < SIZE; j++) A[i][j] = (j+1) * 1.0; b[i] = 1.0 * (i+1); c[i] = 0.0; } printf("\nStarting values of matrix A and vector b:\n"); for (i=0; i < SIZE; i++) { printf(" A[%d]= ",i); for (j=0; j < SIZE; j++) printf("%.1f ",A[i][j]); printf(" b[%d]= %.1f\n",i,b[i]); } printf("\nResults by thread/row:\n"); /* Create a team of threads and scope variables */ #pragma omp parallel shared(A,b,c,total) private(tid,i) { tid = omp_get_thread_num(); /* Loop work-sharing construct - distribute rows of matrix */ #pragma omp for private(j) for (i=0; i < SIZE; i++) { for (j=0; j < SIZE; j++) c[i] += (A[i][j] * b[i]); /* Update and display of running total must be serialized */ #pragma omp critical { total = total + c[i]; printf(" thread %d did row %d\t c[%d]=%.2f\t",tid,i,i,c[i]); printf("Running total= %.2f\n",total); } } /* end of parallel i loop */ } /* end of parallel construct */ printf("\nMatrix-vector total - sum of all c[] = %.2f\n\n",total); return 0; }