OpenMP-Examples/sources/Example_task_reduction.1.c

/*
* @@name:       task_reduction.1c
* @@type:       C
* @@compilable: yes
* @@linkable:   yes
* @@expect:     success
*/

#include<stdlib.h>
#include<stdio.h>
#define N 10

typedef struct node_tag {
    int val;
    struct node_tag *next;
} node_t;

int linked_list_sum(node_t *p)
{
    int res = 0;

    #pragma omp taskgroup task_reduction(+: res)
    {
        node_t* aux = p;
        while(aux != 0)
        {
            #pragma omp task in_reduction(+: res)
            res += aux->val;

            aux = aux->next;
        }
    }
    return res;
}


int main(int argc, char *argv[])
{
    int i;
//                           Create the root node.
    node_t* root = (node_t*) malloc(sizeof(node_t));
    root->val = 1;

    node_t* aux = root;

//                           Create N-1 more nodes.
    for(i=2;i<=N;++i)
    {
        aux->next = (node_t*) malloc(sizeof(node_t));
        aux = aux->next;
        aux->val = i;
    }

    aux->next = 0;

    #pragma omp parallel
    #pragma omp single
    {
        int result = linked_list_sum(root);
        printf( "Calculated: %d  Analytic:%d\n", result, (N*(N+1)/2) );
    }

    return 0;
}