/* sum2.c - Let's modify original thread summation example.
 * Unfortunately, pthread_create allows only one argument as 4th parameter.
 * Compile this way:    gcc sum2.c -pthread -o sum2
 */
#include <pthread.h>
#include <stdio.h>

int sum;
void * runner1 (void * param);
void * runner2 (void * param);

int main(int argc, char *argv[])
{
  pthread_t tid1, tid2;
  pthread_attr_t attr1, attr2;

  if (argc != 2)
  {
    fprintf(stderr, "usage:  sum <integer>\n");
    return -1;
  }

  pthread_attr_init(&attr1);
  pthread_attr_init(&attr2);

  /* Find the sum from 1 to n. */
  pthread_create(&tid1, &attr1, runner1, argv[1]);

  /* Also accumulate the sum of the squares from 1 to n^2. */
  pthread_create(&tid2, &attr2, runner2, argv[1]);
  pthread_join(tid1, NULL);
  pthread_join(tid2, NULL);

  printf("sum = %d\n", sum);
}

void * runner1(void *param)
{
  int i, upper = atoi(param);
  sum = 0;

  for (i = 1; i <= upper; ++i)
  {
    printf("Thread 1 adding %d to the sum\n", i);
    sum += i;
  }
  pthread_exit(0);
}

void * runner2(void *param)
{
  int i, upper = atoi(param);
  sum = 0;

  for (i = 1; i <= upper; ++i)
  {
    printf("Thread 2 adding %d to the sum\n", i);
    sum += i*i;
  }
  pthread_exit(0);
}