libgomp/testsuite/libgomp.c/omp_reduction.c

   1 /******************************************************************************
   2 * FILE: omp_reduction.c
   3 * DESCRIPTION:
   4 *   OpenMP Example - Combined Parallel Loop Reduction - C/C++ Version
   5 *   This example demonstrates a sum reduction within a combined parallel loop
   6 *   construct.  Notice that default data element scoping is assumed - there
   7 *   are no clauses specifying shared or private variables.  OpenMP will
   8 *   automatically make loop index variables private within team threads, and
   9 *   global variables shared.
  10 * AUTHOR: Blaise Barney  5/99
  11 * LAST REVISED: 04/06/05
  12 ******************************************************************************/
  13 #include <omp.h>
  14 #include <stdio.h>
  15 #include <stdlib.h>
  16
  17 int main (int argc, char *argv[]) {
  18
  19 int   i, n;
  20 float a[100], b[100], sum;
  21
  22 /* Some initializations */
  23 n = 100;
  24 for (i=0; i < n; i++)
  25   a[i] = b[i] = i * 1.0;
  26 sum = 0.0;
  27
  28 #pragma omp parallel for reduction(+:sum)
  29   for (i=0; i < n; i++)
  30     sum = sum + (a[i] * b[i]);
  31
  32 printf("   Sum = %f\n",sum);
  33
  34   return 0;
  35 }