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A.14 Using the flush Directive without a List 

The following example (for Section 2.6.5 on page 20) distinguishes the shared objects affected by a flush directive with no list from the shared objects that are not affected:

Example

// omp_flush_without_list.c
#include <omp.h>

int x, *p = &x;

void f1(int *q)
{
    *q = 1;
    #pragma omp flush
    // x, p, and *q are flushed
    //   because they are shared and accessible
    // q is not flushed because it is not shared.
}

void f2(int *q)
{
    #pragma omp barrier
    *q = 2;

    #pragma omp barrier
    // a barrier implies a flush
    // x, p, and *q are flushed
    //   because they are shared and accessible
    // q is not flushed because it is not shared.
}

int g(int n)
{
    int i = 1, j, sum = 0;
    *p = 1;

    #pragma omp parallel reduction(+: sum) num_threads(10)
    {
        f1(&j);
        // i, n and sum were not flushed
        //   because they were not accessible in f1
        // j was flushed because it was accessible
        sum += j;
        f2(&j);
        // i, n, and sum were not flushed
        //   because they were not accessible in f2
        // j was flushed because it was accessible
        sum += i + j + *p + n;
    }
    return sum;
}

int main()
{
}
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