public
	JobMaster (JobType whatToDo, AbstractPage rootPage, int threadsNumber) {
		if (threadsNumber <= 0)
			threadsNumber = CORETHREADS_NUMBER;
		executor = Executors.newFixedThreadPool(threadsNumber);
		assert (executor instanceof ThreadPoolExecutor);
		submittedPairs = new ConcurrentLinkedQueue<>();
		
		this.whatToDo = whatToDo;
		this.rootPage = rootPage; 
	}