main.c

#include <omp.h>
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char **argv)
{
	int num_threads = atoi(argv[1]);
	int n = atoi(argv[2]);

	struct drand48_data *seeds = malloc(n * sizeof(struct drand48_data));
	for (int i = 0; i < n; i++) {
		srand48_r(i, seeds + i);
	}

	omp_set_num_threads(num_threads);

	double begin, end;

	double rnd;

	begin = omp_get_wtime();
	#pragma omp parallel for
	for (int i = 0; i < n; i++) {
		drand48_r(seeds + i, &rnd);
	}
	end = omp_get_wtime();
	printf("elapsed %lf\n", end - begin);

	begin = omp_get_wtime();
	#pragma omp parallel for
	for (int i = 0; i < n; i++) {
		drand48_r(seeds + omp_get_thread_num(), &rnd);
	}
	end = omp_get_wtime();
	printf("elapsed %lf\n", end - begin);

	uint *srand_seeds = calloc(n, sizeof(uint));
	begin = omp_get_wtime();
	#pragma omp parallel for
	for (int i = 0; i < n; i++) {
		rand_r(srand_seeds + i);
	}
	end = omp_get_wtime();
	printf("elapsed %lf\n", end - begin);

	begin = omp_get_wtime();
	#pragma omp parallel for
	for (int i = 0; i < n; i++) {
		rand_r(srand_seeds + omp_get_thread_num());
	}
	end = omp_get_wtime();
	printf("elapsed %lf\n", end - begin);

	free(seeds);
	free(srand_seeds)
	return 0;
}