source: CIVL/examples/omp/dataracebench-1.3.2/micro-benchmarks/original/DRB141-reduction-barrier-orig-no.c

/*
!!!~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~!!!
!!! Copyright (c) 2017-20, Lawrence Livermore National Security, LLC
!!! and DataRaceBench project contributors. See the DataRaceBench/COPYRIGHT file for details.
!!!
!!! SPDX-License-Identifier: (BSD-3-Clause)
!!!~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~!!!
 */


/* To avoid data race, the initialization of the original list item "a" should complete before any
 * update of a as a result of the reduction clause. This can be achieved by adding an explicit
 * barrier after the assignment a=0@26:5, or by enclosing the assignment a=0@26:5 in a single directive
 * or by initializing a@21:7 before the start of the parallel region.
 * */

#include <stdio.h>
#include <omp.h>

int main(){
  int a, i;

  #pragma omp parallel shared(a) private(i)
  {
    #pragma omp master
    a = 0;

    #pragma omp barrier

    #pragma omp for reduction(+:a)
    for (i=0; i<10; i++){
      a += i;
    }

    #pragma omp single
    printf("Sum is %d\n", a);
  }

  return 0;
}