code: private synchronized void requestEvaluator(final int numToRequest) {
      if (numToRequest <= 0) {
        throw new IllegalArgumentException("The number of evaluator request should be a positive integer");
      }
  
      nRequestedEval += numToRequest;
      requestor.newRequest()
          .setMemory(32)
          .setNumber(numToRequest)
          .submit();
    }
docs: Request evaluators. Passing a non positive number is illegal,
  so it does not make a trial for that situation.