Data copying

C | Fortran-90

copyprivate

Definition

copyprivate is a clause that can be used in a single construct; it acts as a mechanism to broadcast the value of a variable private to an implicit task to those of other implicit tasks in the parallel region.

Copy

Feedback

copyprivate(list)

Parameters

list

The variables to pass as copyprivate, separated by commas.

Example

Copy

Feedback

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

/**
 * @brief Illustrates how to use the copyprivate clause.
 * @details This application passes a variable as firstprivate to a parallel
 * region. Then, a single construct receives this variable as a copyprivate and
 * modifies its values. All threads print the value of their own copy before and
 * after the single construct. Although each thread has its own copy, the
 * copyprivate will have broadcasted the new value to all threads after the 
 * single construct.
 **/
int main(int argc, char* argv[])
{
    int a = 123;

    #pragma omp parallel default(none) firstprivate(a)
    {
        printf("Thread %d: a = %d.\n", omp_get_thread_num(), a);

        #pragma omp barrier

        #pragma omp single copyprivate(a)
        {
            a = 456;
            printf("Thread %d executes the single construct and changes a to %d.\n", omp_get_thread_num(), a);
        }

        printf("Thread %d: a = %d.\n", omp_get_thread_num(), a);
    }

    return EXIT_SUCCESS;
}