while(retst) {
      if (qpipe.size() == 0) continue;
      pthread_mutex_lock(&self->mr);
      unsigned long n = qpipe.front();
      qpipe.pop();
      pthread_mutex_unlock(&self->mr);
      self->counter++;
      if (prime(n)) self->primes++;
      if (self->counter%1001 == 0) {
         printf("total numbers:%10lu; primes:%11lu; %% of primes:%7.4f\r", self->counter, self->primes, double(self->primes)/self->counter);
········ fflush(stdout);
      }
   }
   pthread_testcancel();