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  }