libgomp/testsuite/libgomp.c/omp_matvec.c

   1 /******************************************************************************
   2 * OpenMP Example - Matrix-vector multiplication - C/C++ Version
   3 * FILE: omp_matvec.c
   4 * DESCRIPTION:
   5 *   This example multiplies all row i elements of matrix A with vector
   6 *   element b(i) and stores the summed products in vector c(i).  A total is
   7 *   maintained for the entire matrix.  Performed by using the OpenMP loop
   8 *   work-sharing construct.  The update of the shared global total is
   9 *   serialized by using the OpenMP critical directive.
  10 * SOURCE: Blaise Barney  5/99
  11 * LAST REVISED:
  12 ******************************************************************************/
  13
  14 #include <omp.h>
  15 #include <stdio.h>
  16 #define SIZE 10
  17
  18
  19 int
  20 main ()
  21 {
  22
  23 float A[SIZE][SIZE], b[SIZE], c[SIZE], total;
  24 int i, j, tid;
  25
  26 /* Initializations */
  27 total = 0.0;
  28 for (i=0; i < SIZE; i++)
  29   {
  30   for (j=0; j < SIZE; j++)
  31     A[i][j] = (j+1) * 1.0;
  32   b[i] = 1.0 * (i+1);
  33   c[i] = 0.0;
  34   }
  35 printf("\nStarting values of matrix A and vector b:\n");
  36 for (i=0; i < SIZE; i++)
  37   {
  38   printf("  A[%d]= ",i);
  39   for (j=0; j < SIZE; j++)
  40     printf("%.1f ",A[i][j]);
  41   printf("  b[%d]= %.1f\n",i,b[i]);
  42   }
  43 printf("\nResults by thread/row:\n");
  44
  45 /* Create a team of threads and scope variables */
  46 #pragma omp parallel shared(A,b,c,total) private(tid,i)
  47   {
  48   tid = omp_get_thread_num();
  49
  50 /* Loop work-sharing construct - distribute rows of matrix */
  51 #pragma omp for private(j)
  52   for (i=0; i < SIZE; i++)
  53     {
  54     for (j=0; j < SIZE; j++)
  55       c[i] += (A[i][j] * b[i]);
  56
  57     /* Update and display of running total must be serialized */
  58     #pragma omp critical
  59       {
  60       total = total + c[i];
  61       printf("  thread %d did row %d\t c[%d]=%.2f\t",tid,i,i,c[i]);
  62       printf("Running total= %.2f\n",total);
  63       }
  64
  65     }   /* end of parallel i loop */
  66
  67   } /* end of parallel construct */
  68
  69 printf("\nMatrix-vector total - sum of all c[] = %.2f\n\n",total);
  70
  71   return 0;
  72 }
  73