openmp/runtime/test/tasking/hidden_helper_task/capacity_mix_threads.cpp

   1 // RUN: %libomp-cxx-compile-and-run
   2
   3 #include <omp.h>
   4
   5 #include <algorithm>
   6 #include <cassert>
   7 #include <chrono>
   8 #include <thread>
   9 #include <vector>
  10
  11 void dummy_root() {
  12   // omp_get_max_threads() will do middle initialization
  13   int nthreads = omp_get_max_threads();
  14   std::this_thread::sleep_for(std::chrono::milliseconds(1000));
  15 }
  16
  17 int main(int argc, char *argv[]) {
  18   const int N = std::min(std::max(std::max(32, 4 * omp_get_max_threads()),
  19                                   4 * omp_get_num_procs()),
  20                          std::numeric_limits<int>::max());
  21
  22   std::vector<int> data(N);
  23
  24   // Create a new thread to initialize the OpenMP RTL. The new thread will not
  25   // be taken as the "initial thread".
  26   std::thread root(dummy_root);
  27
  28 #pragma omp parallel for num_threads(N)
  29   for (unsigned i = 0; i < N; ++i) {
  30     data[i] = i;
  31   }
  32
  33 #pragma omp parallel for num_threads(N + 1)
  34   for (unsigned i = 0; i < N; ++i) {
  35     data[i] += i;
  36   }
  37
  38   for (unsigned i = 0; i < N; ++i) {
  39     assert(data[i] == 2 * i);
  40   }
  41
  42   root.join();
  43
  44   return 0;
  45 }