OpenMP-Examples/sources/Example_cancellation.2.c

/*
* @@name:	cancellation.2c
* @@type:	C
* @@compilable:	yes
* @@linkable:	no
* @@expect:	success
*/
#include <stddef.h>

typedef struct binary_tree_s {
   int value;
   struct binary_tree_s *left, *right;
} binary_tree_t;

binary_tree_t *search_tree(binary_tree_t *tree, int value, int level) {
    binary_tree_t *found = NULL;
    if (tree) {
        if (tree->value == value) {
            found = tree;
        }
        else {
#pragma omp task shared(found) if(level < 10)
            {
                binary_tree_t *found_left = NULL;
                found_left = search_tree(tree->left, value, level + 1);
                if (found_left) {
#pragma omp atomic write
                    found = found_left;
#pragma omp cancel taskgroup
                }
            }
#pragma omp task shared(found) if(level < 10)
            {
                binary_tree_t *found_right = NULL;
                found_right = search_tree(tree->right, value, level + 1);
                if (found_right) {
#pragma omp atomic write
                    found = found_right;
#pragma omp cancel taskgroup
                }
            }
#pragma omp taskwait
        }
    }
    return found;
}
binary_tree_t *search_tree_parallel(binary_tree_t *tree, int value) {
    binary_tree_t *found = NULL;
#pragma omp parallel shared(found, tree, value)
    {
#pragma omp master
        {
#pragma omp taskgroup
            {
                found = search_tree(tree, value, 0);
            }
        }
    }
    return found;
}