a3c.py 文件源码

def pull_batch_from_queue(self):
        """
        Take a rollout from the queue of the thread runner.
        """
        # get top rollout from queue (FIFO)
        rollout = self.runner.queue.get(timeout=600.0)
        while not rollout.terminal:
            try:
                # Now, get remaining *available* rollouts from queue and append them into
                # the same one above. If queue.Queue(5): len=5 and everything is
                # superfast (not usually the case), then all 5 will be returned and
                # exception is raised. In such a case, effective batch_size would become
                # constants['ROLLOUT_MAXLEN'] * queue_maxlen(5). But it is almost never the
                # case, i.e., collecting  a rollout of length=ROLLOUT_MAXLEN takes more time
                # than get(). So, there are no more available rollouts in queue usually and
                # exception gets always raised. Hence, one should keep queue_maxlen = 1 ideally.
                # Also note that the next rollout generation gets invoked automatically because
                # its a thread which is always running using 'yield' at end of generation process.
                # To conclude, effective batch_size = constants['ROLLOUT_MAXLEN']
                rollout.extend(self.runner.queue.get_nowait())
            except queue.Empty:
                break
        return rollout