openmp/runtime/test/tasking/taskdep_if0_2.c

   1 // RUN: %libomp-compile-and-run
   2
   3 #include <stdio.h>
   4 #include <stdlib.h>
   5 #include <omp.h>
   6 #include "omp_my_sleep.h"
   7
   8 int a = 0, b = 0;
   9 int task_grabbed = 0, task_can_proceed = 0;
  10 int task2_grabbed = 0, task2_can_proceed = 0;
  11
  12 static void wait_on_flag(int *flag) {
  13   int flag_value;
  14   int timelimit = 30;
  15   int secs = 0;
  16   do {
  17     #pragma omp atomic read
  18     flag_value = *flag;
  19     my_sleep(1.0);
  20     secs++;
  21     if (secs == timelimit) {
  22       fprintf(stderr, "error: timeout in wait_on_flag()\n");
  23       exit(EXIT_FAILURE);
  24     }
  25   } while (flag_value == 0);
  26 }
  27
  28 static void signal_flag(int *flag) {
  29   #pragma omp atomic
  30   (*flag)++;
  31 }
  32
  33 int main(int argc, char** argv) {
  34
  35   // Ensure two threads are running
  36   int num_threads = omp_get_max_threads();
  37   if (num_threads < 2)
  38     omp_set_num_threads(2);
  39
  40   #pragma omp parallel shared(a)
  41   {
  42     int a_value;
  43     // Let us be extra safe here
  44     if (omp_get_num_threads() > 1) {
  45       #pragma omp single nowait
  46       {
  47         // Schedule independent child task that
  48         // waits to be flagged after sebsequent taskwait depend()
  49         #pragma omp task
  50         {
  51           signal_flag(&task_grabbed);
  52           wait_on_flag(&task_can_proceed);
  53         }
  54         // Let another worker thread grab the task to execute
  55         wait_on_flag(&task_grabbed);
  56         // This should be ignored since the task above has
  57         // no dependency information
  58         #pragma omp task if(0) depend(inout: a)
  59         {}
  60         // Signal the independent task to proceed
  61         signal_flag(&task_can_proceed);
  62
  63         // Schedule child task with dependencies that taskwait does
  64         // not care about
  65         #pragma omp task depend(inout: b)
  66         {
  67           signal_flag(&task2_grabbed);
  68           wait_on_flag(&task2_can_proceed);
  69           #pragma omp atomic
  70           b++;
  71         }
  72         // Let another worker thread grab the task to execute
  73         wait_on_flag(&task2_grabbed);
  74         // This should be ignored since the task above has
  75         // dependency information on b instead of a
  76         #pragma omp task if(0) depend(inout: a)
  77         {}
  78         // Signal the task to proceed
  79         signal_flag(&task2_can_proceed);
  80
  81         // Generate one child task for taskwait
  82         #pragma omp task shared(a) depend(inout: a)
  83         {
  84           my_sleep(1.0);
  85           #pragma omp atomic
  86           a++;
  87         }
  88         #pragma omp task if(0) depend(inout: a)
  89         {}
  90
  91         #pragma omp atomic read
  92         a_value = a;
  93
  94         if (a_value != 1) {
  95           fprintf(stderr, "error: dependent task was not executed before "
  96                           "taskwait finished\n");
  97           exit(EXIT_FAILURE);
  98         }
  99       } // #pragma omp single
 100     } // if (num_threads > 1)
 101   } // #pragma omp parallel
 102
 103   return EXIT_SUCCESS;
 104 }