#include <pthread.h>
#include <sys/time.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

/* #define DEBUG */
/* #define PROFILING */	
#define ITERATIONS 1024 
#define	NUM_THREADS 1024 
#define MAX_SLEEP 1000000

useconds_t musec[ITERATIONS];
unsigned long seed = 62;
pthread_t tid[NUM_THREADS];
int id[NUM_THREADS];

void
timevalsub(struct timeval *t1, const struct timeval *t2)
{

        t1->tv_sec -= t2->tv_sec;
        t1->tv_usec -= t2->tv_usec;

        if (t1->tv_usec < 0) {
                t1->tv_sec--;
                t1->tv_usec += 1000000;
        }
        if (t1->tv_usec >= 1000000) {
                t1->tv_sec++;
                t1->tv_usec -= 1000000;
        }
}


static void  
init(void)
{
	int i;
	
	srandom(seed);
	for (i = 0; i < ITERATIONS; ++i) { 
		musec[i] = random() % MAX_SLEEP;
#ifdef DEBUG
		printf("Iteration: %d num: %d \n", i, musec[i]); 
#endif
	}				
	return;
}

static void
do_usleep(int *tid) 
{
	int i, step;
	
	i = 0;
	for(;;) {
		step = (i + *tid) % ITERATIONS;
#ifdef DEBUG
		printf("Id: %d iter: %d num: %d \n", pthread_self(), i, 
		    musec[step]);	
#endif
		usleep(musec[step]);
		if (i < ITERATIONS)
			i++;
		else 
			break;
	}
	return;
}

int
main(void)
{
	int i, r_val;
#ifdef PROFILING
	struct timeval btp, atp;
#endif

	init();
#ifdef PROFILING	
	gettimeofday(&btp, NULL);	
#endif
	for (i = 0; i < NUM_THREADS; ++i) {
		id[i] = i;
		r_val = pthread_create(&tid[i], NULL, (void *) &do_usleep, 
		    &id[i]);
		if (r_val == -1)
			perror("Error in pthread_create()\n");
	}
	for (i = 0; i < NUM_THREADS; ++i) {
		r_val = pthread_join(tid[i], NULL);
		if (r_val == -1)
			perror("Error in pthread_join()\n");
	}
#ifdef PROFILING
	gettimeofday(&atp, NULL);	
	timevalsub(&atp, &btp);	
	printf("Time elapsed: %ld.%ld \n", atp.tv_sec, atp.tv_usec);
#endif
	return (0);
}