65 lines
1.9 KiB
C
65 lines
1.9 KiB
C
// RUN: %libomp-compile && env KMP_ENABLE_TASK_THROTTLING=0 %libomp-run
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// RUN: %libomp-compile && env KMP_ENABLE_TASK_THROTTLING=1 %libomp-run
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#include<omp.h>
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#include<stdlib.h>
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#include<string.h>
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/**
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* Test the task throttling behavior of the runtime.
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* Unless OMP_NUM_THREADS is 1, the master thread pushes tasks to its own tasks
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* queue until either of the following happens:
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* - the task queue is full, and it starts serializing tasks
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* - all tasks have been pushed, and it can begin execution
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* The idea is to create a huge number of tasks which execution are blocked
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* until the master thread comes to execute tasks (they need to be blocking,
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* otherwise the second thread will start emptying the queue).
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* At this point we can check the number of enqueued tasks: iff all tasks have
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* been enqueued, then there was no task throttling.
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* Otherwise there has been some sort of task throttling.
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* If what we detect doesn't match the value of the environment variable, the
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* test is failed.
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*/
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#define NUM_TASKS 2000
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int main()
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{
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int i;
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int block = 1;
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int throttling = strcmp(getenv("KMP_ENABLE_TASK_THROTTLING"), "1") == 0;
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int enqueued = 0;
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int failed = -1;
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#pragma omp parallel num_threads(2)
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#pragma omp master
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{
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for (i = 0; i < NUM_TASKS; i++) {
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enqueued++;
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#pragma omp task
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{
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int tid;
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tid = omp_get_thread_num();
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if (tid == 0) {
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// As soon as the master thread starts executing task we should unlock
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// all tasks, and detect the test failure if it has not been done yet.
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if (failed < 0)
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failed = throttling ? enqueued == NUM_TASKS : enqueued < NUM_TASKS;
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#pragma omp atomic write
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block = 0;
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}
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int wait = 0;
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do {
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#pragma omp atomic read
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wait = block;
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} while (wait);
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}
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}
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block = 0;
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}
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return failed;
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}
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