#define SORT_LIST 128

#include <pthread.h>
#include <stdio.h>


void *compare_exchange();
int sort_array[SORT_LIST];
int j;

main()
{
        clock_t t1, t2;
        pthread_attr_t  attr;
	pthread_t *p_threads;
	int i, ii;

	/* we need half as many threads as number of elements */
	p_threads = (pthread_t *) malloc((SORT_LIST/2) * sizeof(pthread_t));

	pthread_attr_init (&attr);
        pthread_attr_setscope (&attr,PTHREAD_SCOPE_SYSTEM);


	/* set up array here */

	for (i=0; i< SORT_LIST; i++)
		sort_array[i] = rand() % 1000;

	t1 = clock();
	for (ii = 0; ii < SORT_LIST; ii++)
	{
		for (i=0; i< SORT_LIST / 2 - ii % 2; i++)
		{
			j = 2 * i + (ii % 2);
			pthread_create(&p_threads[i], &attr,
					compare_exchange,
					(void *)&sort_array[j]);
		}
		for (i=0; i< SORT_LIST / 2 - ii % 2; i++)
		{
			pthread_join(p_threads[i], NULL);
		}
	}

	t2 = clock();
        printf("CPU time (not wall clock time) %f\n", (float)t2/1000000);
	for (i=0; i< SORT_LIST; i++)
		printf("%d ", sort_array[i]);
	printf("\n");
}

void *compare_exchange(int *s)
{
	int temp;

	if (s[0] > s[1])
	{
		temp = s[0];
		s[0] = s[1];
		s[1] = temp;
	}
	pthread_exit(0);
}