/*
 pthread3.c  Race condition
 $ g++ -Wall -lpthread pthread3.c++ 
 $ ./a.out 500000
 output:  0, +ve and -ve
*/
#include <iostream>
using namespace std;
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>

int times, n = 0 ;
void * thread1(void *) ;
void * thread2(void *) ;
void inc() {n=n+1;}
void dec() {n=n-1;}

int main(int count, char *vect[]) { // argument is data for times
     pthread_t thID1, thID2; 

     if(count < 2) {
          perror("No argument for times\n") ;
          exit(1) ;
     }     
     times = atoi(vect[1]) ;
     pthread_create(&thID1, NULL, thread1, NULL) ;
     pthread_create(&thID2, NULL, thread2, NULL) ;
     pthread_join(thID1, NULL) ;     
     pthread_join(thID2, NULL) ;

     cout << "n: " << n << "\n" ;     
     return 0 ;
}

void *thread1(void *vp) {
     int i ;

     for(i=1; i<=times; ++i) inc();
     return NULL ;
}

void *thread2(void *vp) {
     int i ;

     for(i=1; i<=times; ++i) dec() ; 
     return NULL ;
}