Reduction Variables

#pragma MP taskloop reduction (list_of_reduction_variables) specifies that all the variables appearing in the reduction list will be treated as reduction variables for the loop. A reduction variable is one whose partial values can be individually computed by each of the processors processing iterations of the loop, and whose final value can be computed from all its partial values. The presence of a list of reduction variables can facilitate the compiler in identifying that the loop is a reduction loop, allowing generation of parallel reduction code for it. Consider the following example:

#pragma MP taskloop reduction(x)
    for (i=0; i<n; i++) {
         x = x + a[i];
}

the variable x is a (sum) reduction variable and the i loop is a(sum) reduction loop.