omp_task_red_taskloop.c

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// RUN: %libomp-compile-and-run
 
// Parsing error until gcc8:
// UNSUPPORTED: gcc-4, gcc-5, gcc-6, gcc-7, gcc-8
 
// Parsing error until clang11:
// UNSUPPORTED: clang-10, clang-9, clang-8, clang-7
 
// No icc compiler support yet
// XFAIL: icc
 
#include <stdio.h>
#include <omp.h>
 
int r;
 
int work(int k, int l)
{
  return k + l + 1;
}
void bar(int i) {
  #pragma omp taskgroup task_reduction(+:r)
 { int th_gen = omp_get_thread_num();
  #pragma omp task in_reduction(+:r) firstprivate(i, th_gen)
  {
    r += work(i, 0);
printf("executing task (%d, 0), th %d (gen by th %d)\n", i, omp_get_thread_num(), th_gen);
  }
  #pragma omp task in_reduction(+:r) firstprivate(i, th_gen)
  {
    r += work(i, 1);
printf("executing task (%d, 1), th %d (gen by th %d)\n", i, omp_get_thread_num(), th_gen);
  }
 }
}
int foo() {
  int i;
  int th_gen = omp_get_thread_num();
  #pragma omp taskgroup task_reduction(+:r)
  {
    bar(0);
  }
printf("th %d passed bar0\n", th_gen);
  #pragma omp taskloop reduction(+:r) firstprivate(th_gen)
  for (i = 1; i < 4; ++i) {
    bar(i);
printf("th %d (gen by th %d) passed bar%d in taskloop\n", omp_get_thread_num(), th_gen, i);
  #pragma omp task in_reduction(+:r)
    r += i;
  }
  return 0;
}
// res = ((1+2)+(2+3)+(3+4)+(4+5)+1+2+3) = 30
#define res 30
int main()
{
  r = 0;
  #pragma omp parallel num_threads(2)
  { // barrier ensures threads have started before tasks creation
    #pragma omp barrier
    // single ensures no race condition between taskgroup reductions
    #pragma omp single nowait
      foo();
  }
  if (r == res) {
    return 0;
  } else {
    printf("error r = %d (!= %d)\n", r, res);
    return 1;
  }
}