#ifndef _OPENMP
#error Please compile me with OpenMP enabled
#endif

#include <omp.h>
#include <pthread.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

enum { OMP_THREADS=3 };

pthread_barrier_t barrier1, barrier2;

static void * do_fork(void * unused) {
	int sum = 0;
	puts("In child, before OpenMP loop1");
	#pragma omp parallel for num_threads(OMP_THREADS) reduction(+:sum)
	for (int i = 0; i < 100; ++i) {
		sum += i;
	}
	printf("In child, OpenMP loop1 done (%d)\n", sum);

	pthread_barrier_wait(&barrier1);
#ifndef OMIT_PAUSE_RESOURCE_ALL
	omp_pause_resource_all(omp_pause_hard);
#endif
	pid_t ret = fork();
	if (ret < 0) abort();
	if (ret > 0) {
		pthread_barrier_wait(&barrier2);
		return NULL;
	}
	puts("In child, before OpenMP loop2");
	sum = 0;
	#pragma omp parallel for num_threads(OMP_THREADS) reduction(+:sum)
	for (int i = 0; i < 100; ++i) {
		sum += i;
	}
	printf("In child, OpenMP loop2 done (%d)\n", sum);
	exit(0);
}


int main() {
	if (pthread_barrier_init(&barrier1, NULL, OMP_THREADS+1)) abort();
	if (pthread_barrier_init(&barrier2, NULL, OMP_THREADS+1)) abort();

	pthread_t t;
	int ret = pthread_create(&t, NULL, do_fork, NULL);
	if (ret) abort();

	puts("Starting parent loop");

	bool waited1=false, waited2=false;
	int sum = 0;
	#pragma omp parallel for num_threads(OMP_THREADS) private(waited1, waited2) reduction(+:sum)
	for (size_t i = 0; i < OMP_THREADS*10; ++i) {
		//do_fork(NULL);
		if (!waited1) {
			pthread_barrier_wait(&barrier1);
			waited1=true;
		}
		sum += i;
		if (!waited2) {
			pthread_barrier_wait(&barrier2);
			waited2=true;
		}
	}

	printf("Parent loop1 done (%d), attaching child thread...\n", sum);
	ret = pthread_join(t, NULL);
	printf("...ret=%d\n", ret);

	sum = 0;
	#pragma omp parallel for num_threads(OMP_THREADS) private(waited1, waited2) reduction(+:sum)
	for (size_t i = 0; i < OMP_THREADS*10; ++i) {
		sum += i;
	}

	printf("Parent loop2 done (%d)\n", sum);
}