Minor fixes to HER release (#319)

* Fix plotting script

* Add warning if num_cpu = 1

baselines/her/experiment/plot.py

@@ -67,13 +67,13 @@ for curr_path in paths:
         print('skipping {}'.format(curr_path))
         continue
     print('loading {} ({})'.format(curr_path, len(results['epoch'])))
-    with open(os.path.join(curr_path, 'metadata.json'), 'r') as f:
+    with open(os.path.join(curr_path, 'params.json'), 'r') as f:
-        metadata = json.load(f)
+        params = json.load(f)
 
     success_rate = np.array(results['test/success_rate'])
     epoch = np.array(results['epoch']) + 1
-    env_id = metadata['kwargs']['env_name']
+    env_id = params['env_name']
-    replay_strategy = metadata['kwargs']['replay_strategy']
+    replay_strategy = params['replay_strategy']
 
     if replay_strategy == 'future':
         config = 'her'

baselines/her/experiment/train.py

@@ -119,6 +119,18 @@ def launch(
     params = config.prepare_params(params)
     config.log_params(params, logger=logger)
 
+    if num_cpu == 1:
+        logger.warn()
+        logger.warn('*** Warning ***')
+        logger.warn(
+            'You are running HER with just a single MPI worker. This will work, but the ' +
+            'experiments that we report in Plappert et al. (2018, https://arxiv.org/abs/1802.09464) ' +
+            'were obtained with --num_cpu 19. This makes a significant difference and if you ' +
+            'are looking to reproduce those results, be aware of this. Please also refer to ' + 
+            'https://github.com/openai/baselines/issues/314 for further details.')
+        logger.warn('****************')
+        logger.warn()
+
     dims = config.configure_dims(params)
     policy = config.configure_ddpg(dims=dims, params=params, clip_return=clip_return)