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 main ()
  20 {
  21
  22 float A[SIZE][SIZE], b[SIZE], c[SIZE], total;
  23 int i, j, tid;
  24
  25 /* Initializations */
  26 total = 0.0;
  27 for (i=0; i < SIZE; i++)
  28   {
  29   for (j=0; j < SIZE; j++)
  30     A[i][j] = (j+1) * 1.0;
  31   b[i] = 1.0 * (i+1);
  32   c[i] = 0.0;
  33   }
  34 printf("\nStarting values of matrix A and vector b:\n");
  35 for (i=0; i < SIZE; i++)
  36   {
  37   printf("  A[%d]= ",i);
  38   for (j=0; j < SIZE; j++)
  39     printf("%.1f ",A[i][j]);
  40   printf("  b[%d]= %.1f\n",i,b[i]);
  41   }
  42 printf("\nResults by thread/row:\n");
  43
  44 /* Create a team of threads and scope variables */
  45 #pragma omp parallel shared(A,b,c,total) private(tid,i)
  46   {
  47   tid = omp_get_thread_num();
  48
  49 /* Loop work-sharing construct - distribute rows of matrix */
  50 #pragma omp for private(j)
  51   for (i=0; i < SIZE; i++)
  52     {
  53     for (j=0; j < SIZE; j++)
  54       c[i] += (A[i][j] * b[i]);
  55
  56     /* Update and display of running total must be serialized */
  57     #pragma omp critical
  58       {
  59       total = total + c[i];
  60       printf("  thread %d did row %d\t c[%d]=%.2f\t",tid,i,i,c[i]);
  61       printf("Running total= %.2f\n",total);
  62       }
  63
  64     }   /* end of parallel i loop */
  65
  66   } /* end of parallel construct */
  67
  68 printf("\nMatrix-vector total - sum of all c[] = %.2f\n\n",total);
  69
  70   return 0;
  71 }
  72