#include <cstdio>

#include <omp.h>

int main(int argc, char* argv[])

{

const int expected = 1;

bool failed = false;

// Variable only modified in critical section

int criticalVar = expected;

int randomValue = 2;

#pragma omp parallel for num_threads(4) default(none) \

shared(randomValue, criticalVar, expected, failed)

for (int i = 0; i < 1000; i++) {

#pragma omp critical

{

if (criticalVar != expected) {

printf("Thread %d critical unexpected %d != %d\n",

omp_get_thread_num(),

criticalVar,

expected);

failed = true;

}

// Do a load of modifications to the critical variable that will be

// picked up by other threads if the critical isn't working.

criticalVar = 2;

for (int j = 0; j < 10000; j++) {

criticalVar = (criticalVar + randomValue) % 4 + 10;

}

randomValue = ((omp_get_thread_num() + 1) * randomValue) % 7;

// Set back to original value

criticalVar = expected;

}

}

if (failed || criticalVar != expected) {

printf("Critical section error, assumption failed: %d\n", criticalVar);

return EXIT_FAILURE;

}

return EXIT_SUCCESS;

}