Pthreads on Mac OS X - a problem with mutexes

I am trying to learn how to program parallel algorithms in C using POSIX streams. My environment is Mac OS X 10.5.5 with gcc 4.

Compilation:

gcc -Wall -D_REENTRANT -lpthread source.c -o test.o

      

        
        
        
      

    

So my problem is that if I compile this in an Ubuntu 9.04 box, it runs smoothly in thread order, looks like mutexes on Mac, doesn't work, and threads don't wait for general information.

Mac:

#1
#0
#2
#5
#3
#4

      

        
        
        
      

    

ubuntu

#0
#1
#2
#3
#4
#5

      

        
        
        
      

    

Any ideas?

Follow below source code:

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

#define NUM_THREADS 6
pthread_mutex_t mutexsum;
pthread_t threads[NUM_THREADS];
long Sum;

void *SumThreads(void *threadid){
    int tmp;
    int i,x[10],y[10];

    // Para cada x e y do vetor, jogamos o valor de i, só para meio didáticos
    for (i=0; i<10 ; i++){
        x[i] = i;
        y[i] = i;
    }


    tmp = Sum;
     for (i=0; i<10 ; i++){
         tmp += (x[i] * y[i]);
     }

       pthread_mutex_lock (&mutexsum);
       Sum += tmp;
       printf("Im thread #%ld sum until now is: %ld\n",threadid,Sum);
       pthread_mutex_unlock (&mutexsum);
       return 0;
}


int main(int argc, char *argv[]){
    int i;
    Sum = 0;

    pthread_mutex_init(&mutexsum, NULL);

    for(i=0; i<NUM_THREADS; i++){
        pthread_create(&threads[i], NULL, SumThreads, (void *)i);
    }

    pthread_exit(NULL);
}