/*
Note To compile thread-based programs you must use the -pthread compiler option.
This ensures linking with the libpthread library and with the thread-safe
functions of the C library.

IMP. Follow an incremental code development approach. If you write all the code
in a single go and only then compile it, you risk spending the following 15
minutes eliminating the compilation errors and the remaining class debugging it.
Instead, you should add code step by step, compiling it and testing it, after
each step.

In this problem you will write a very simple multi-threaded program that
increments a shared counter.
The program's main thread creates 3 other threads.

Each ot these 3 threads shall increment a shared counter (long int) a number of
times, specified as a command line argument to the program.

The main thread shall wait for the termination of the other 3 threads, and then
shall print the final value of the counter.

Compile your program and run it several times. Explain the observed results.
*/
#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>


typedef struct __myarg_t{
  long int counter;
  long int num_increments;
} myarg_t;

void *increment(void *args){
  myarg_t *res = (myarg_t *) args;

  for(int i = 0; i < res->num_increments; i++){
    ++res->counter;
  }
  return (void *) res->counter;
}

int main(int argc, char* argv[]){
  if(argc == 2){
    myarg_t args;

    args.counter = 0;
    args.num_increments = atoi(argv[1]);

    long int tcounter[3];

    pthread_t t[3];

    for(int i = 0; i < 3; i++){
    tcounter[i] = pthread_create(&t[i], NULL, increment, &args);
    }

    for(int i = 0; i < 3; i++){
        pthread_join(t[i], (void **) &tcounter[i]);
    printf("Thread %d has counter = %ld\n", i+1, tcounter[i]);
    }

    printf("%ld\n", args.counter);

  }
  else if (argc < 2) printf("Few Arguments!\n");
  else printf("Too Many Arguments!\n");
}