Parallel ball

parallel.c

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

#define MAX_CONCURRENT 10

pthread_mutex_t mutex;
pthread_cond_t condvar;

int race[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
int winner[10];
int done = -1;
int parallel_round = 0;
int concurrent = 0;

void shuffle(int *array, size_t n)
{
    if (n > 1) 
    {
        struct timeval tv;
        gettimeofday(&tv, NULL);
        int usec = tv.tv_usec;
        srand48(usec);

        size_t i;
        for (i = 0; i < n - 1; i++) 
        {
            size_t j = (unsigned int) (drand48()*(i+1));

            int t = array[j];
            array[j] = array[i];
            array[i] = t;
        }
    }
}

void *task(int id) {

    int wait = 1000000 * race[id];

    usleep(wait);

    if (done != 0) {
        done = 0;
        printf("Ball %d got %d\n", parallel_round + 1, id);
        pthread_cond_signal(&condvar);
        winner[parallel_round++] = id;
    } else {
        pthread_cond_signal(&condvar);
    }
}

void *threaded_task(void *t) {
    long id = (long) t;
    concurrent++;
    task(id);
    concurrent--;
    pthread_exit(0);
}

void *parallel(int num_tasks)
{
    int num_threads = num_tasks;
    pthread_t thread[num_threads];
    int rc;
    long t;
    for (t = 0; t < num_threads; t++) {
        rc = pthread_create(&thread[t], NULL, threaded_task, (void *)t);
        if (rc) {
            printf("ERROR: return code from pthread_create() is %d\n", rc);
            exit(-1);
        }
    }
}

int main() {

    pthread_mutex_init(&mutex, NULL);
    pthread_cond_init(&condvar, NULL);    

    for (int i = 0; i < 7; i++) {

        done = -1;

        shuffle((int*) &race, 10);
        parallel(10);

        pthread_mutex_lock(&mutex);
        pthread_cond_wait(&condvar, &mutex);
        pthread_mutex_unlock(&mutex);

        while (concurrent > MAX_CONCURRENT) {
            printf("Wait for reach maxmimum concurrent\n");
            usleep(300000);
        }
    }

    printf("-------------------------\n");
    printf("Main completed\n");
    printf("-------------------------\n");

    printf("-------------------------\n");
    printf("Winner is %d %d %d %d %d %d %d\n", winner[0], winner[1], winner[2], winner[3], winner[4], winner[5], winner[6]);
    printf("-------------------------\n");

    pthread_exit(NULL);
}