A.14 Using the flush Directive without a List

 

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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

Code

// 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()  
{  
}