/*
 * ISA 563, Spring 2011
 * Copyleft by Muhammad Abdulla
 */


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

/*
 *  unorderly_threads.c -- demonstrates potential problems with unsynchronized manipulation of shared variables
 */

#define MAXTH     20 
#define MAX       50000

int arr[MAX+MAXTH];
int idx; // global index to array

void *fill_array(void *tid)
{
    while ( idx < MAX ) {
       arr[idx] = idx;
       idx++;
    }
    pthread_exit(NULL);
}


int main(int argc, char *argv[])
{
    int rc;
    int i;

    pthread_t threads[MAXTH];

    for( i = 0; i < MAXTH; i++) {
        rc = pthread_create(&threads[i], NULL, fill_array, (void *)i);
        if (rc) {
            printf("ERROR; return code from pthread_create() is %d\n", rc);
            exit(-1);
        }
    }

    for ( i = 0; i < MAXTH; i++ ) {
       rc = pthread_join(threads[i], NULL);
    }

    // print all entries that have been messed up by unoderly modification and access by threads
    for ( i = 0; i < MAX; i++ ) {
       if ( arr[i] != i ) {
          fprintf(stderr, "arr[%d]: %d\n", i, arr[i]);
       }
    }

    pthread_exit(NULL);
}