lock for atari simulator init

examples/Atari2600/common.py

@@ -52,7 +52,6 @@ def eval_with_funcs(predict_funcs, nr_eval):
 
     for k in threads:
         k.start()
-        time.sleep(0.1) # avoid simulator bugs
     stat = StatCounter()
     try:
         for _ in tqdm(range(nr_eval)):

tensorpack/RL/atari.py

@@ -7,6 +7,7 @@ import numpy as np
 import time, os
 import cv2
 from collections import deque
+import threading
 import six
 from six.moves import range
 from ..utils import get_rng, logger, memoized, get_dataset_dir
@@ -25,6 +26,8 @@ __all__ = ['AtariPlayer']
 def log_once():
     logger.warn("https://github.com/mgbellemare/Arcade-Learning-Environment/pull/171 is not merged!")
 
+_ALE_LOCK = threading.Lock()
+
 class AtariPlayer(RLEnvironment):
     """
     A wrapper for atari emulator.
@@ -50,17 +53,19 @@ class AtariPlayer(RLEnvironment):
             rom_file = os.path.join(get_dataset_dir('atari_rom'), rom_file)
         assert os.path.isfile(rom_file), "rom {} not found".format(rom_file)
 
+        try:
+            ALEInterface.setLoggerMode(ALEInterface.Logger.Warning)
+        except AttributeError:
+            log_once()
+
+        # avoid simulator bugs: https://github.com/mgbellemare/Arcade-Learning-Environment/issues/86
+        with _ALE_LOCK:
             self.ale = ALEInterface()
             self.rng = get_rng(self)
 
             self.ale.setInt("random_seed", self.rng.randint(0, 10000))
             self.ale.setBool("showinfo", False)
 
-        try:
-            ALEInterface.setLoggerMode(ALEInterface.Logger.Warning)
-        except AttributeError:
-            log_once()
-
             self.ale.setInt("frame_skip", 1)
             self.ale.setBool('color_averaging', False)
             # manual.pdf suggests otherwise.