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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 <omp.h>
- #include <stdio.h>
- #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;
- }
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