#define GRAIN		2000
#define	LIMIT		100000
#define NUM_INIT_PRIME  15

int primes[LIMIT/10+1] =
  {2,3, 5, 7, 11, 13, 17, 19, 23, 29, 31,  37,  41, 43,  47};
int p2[LIMIT/10+1] = 
  {4,9,25,49,121,169,289,361,529,841,961,1369, 1681,1849,2209};

real_main(argc, argv)
     int argc;
     char *argv[];
{
  int	eot, first_num, i, new_primes[GRAIN], np2;
  int	num, num_primes, num_workers, length, worker();

  num_workers = atoi(argv[1]);
  for (i = 0; i < num_workers; ++i) eval("worker", worker());

  num_primes = NUM_INIT_PRIME;
  first_num = primes[num_primes-1] + 2;

  out("next task", first_num);
  
  eot = 0;	/* becomes 1 at "end of table" -- i.e., table complete */
  for (num = first_num; num < LIMIT; num += GRAIN) {
    in("result", num, ? new_primes : length);

    for (i = 0; i < length; ++i, ++num_primes) {
      primes[num_primes] = new_primes[i];

      if (!eot) {
	np2 = new_primes[i]*new_primes[i];
	if (np2 > LIMIT) {
	  eot = 1;
	  np2 = -1;
	}
	out("primes", num_primes, new_primes[i], np2);
      }
    }
  }
  /*  " ? int" means  "match any int; throw out the value" */
  for (i = 0; i < num_workers; ++i) in("worker", ? int);

  printf("%d: %d\n", num_primes, primes[num_primes-1]);
}

worker()
{
  int	count, eot, i, limit, num, num_primes, ok, start;
  int	my_primes[GRAIN];

  num_primes = NUM_INIT_PRIME;

  eot = 0;
  while(1) {
    in("next task", ? num);
    if (num == -1) {
      out("next task", -1);
      return;
    }
    limit = num + GRAIN;
    out("next task", (limit > LIMIT) ? -1 : limit);
    if (limit > LIMIT) limit = LIMIT;

    start = num;
    for (count = 0; num < limit; num += 2) {
      while (!eot && num > p2[num_primes-1]) {
        rd("primes", num_primes, ? primes[num_primes], ? p2[num_primes]);
        if (p2[num_primes] < 0)
          eot = 1;
        else
          ++num_primes;
      }
      for (i = 1, ok = 1; i < num_primes; ++i) {
        if (!(num%primes[i])) {
          ok = 0;
          break;
        }
        if (num < p2[i]) break;
      }
      if (ok) {
        my_primes[count] = num;
        ++count;
      }
    }
    /* Send the control process any primes found. */
    out("result", start, my_primes : count);
  }
}