Master.double dqn bug fix (#315)

* issue#264 bug fix

* double DQN bug fix

* rm print

Co-authored-by: ysqyang <v-yangqi@microsoft.com>

maro/rl/agent/dqn.py

@@ -109,11 +109,12 @@ class DQN(AbsAgent):
 
         q_all = self._get_q_values(states)
         q = select_by_actions(q_all, actions)
-        next_q_all = self._get_q_values(next_states, is_eval=False, training=False)
+        next_q_all_target = self._get_q_values(next_states, is_eval=False, training=False)
         if self.config.double:
-            next_q = select_by_actions(next_q_all)  # (N,)
+            next_q_all_eval = self._get_q_values(next_states, training=False)
+            next_q = select_by_actions(next_q_all_target, next_q_all_eval.max(dim=1)[1])  # (N,)
         else:
-            next_q, _ = get_max(next_q_all)  # (N,)
+            next_q, _ = get_max(next_q_all_target)  # (N,)
 
         loss = get_td_errors(q, next_q, rewards, self.config.reward_discount, loss_func=self.config.loss_func)
         self.model.step(loss.mean())