Example 3
It is even possible to have multiple
reduction clauses in the
same parallel region.
<![CDATA[
// File: example3.cpp
//
#include <stdio.h>
#include <omp.h>
int main() {
int reps = 10000 ;
long int A[reps] ;
long int B[reps] ;
long int sumA = 0 ;
long int sumB = 0 ;
for (long int i=0; i < reps ; i++) {
A[i] = i ;
B[i] = 2*i ;
}
omp_set_dynamic(0) ;
#pragma omp parallel shared(A,B,sumA,sumB,reps) num_threads(4)
{
#pragma omp single
{ // only one thread has to do this
// omp_set_num_threads(4);
printf("Number of threads = %d\n", omp_get_num_threads() ) ;
}
#pragma omp for schedule(static,10) reduction(+:sumA) reduction(+:sumB)
for (long int i=0; i < reps; i++) {
sumA += A[i] ;
sumB += B[i] ;
}
} // end of parallel region
printf("sumA = %ld\n", sumA) ;
printf("sumB = %ld\n", sumB) ;
return 0 ;
}
]]>
Download: example3.cpp
Download this program. Then, compile and run it a few times.