Avoid using default config while requesting available GPUs (#863)

baselines/common/tf_util.py

@@ -305,12 +305,17 @@ def display_var_info(vars):
     logger.info("Total model parameters: %0.2f million" % (count_params*1e-6))
 
 
-def get_available_gpus():
-    # recipe from here:
-    # https://stackoverflow.com/questions/38559755/how-to-get-current-available-gpus-in-tensorflow?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa
+def get_available_gpus(session_config=None):
+    # based on recipe from https://stackoverflow.com/a/38580201
+
+    # Unless we allocate a session here, subsequent attempts to create one
+    # will ignore our custom config (in particular, allow_growth=True will have
+    # no effect).
+    if session_config is None:
+        session_config = get_session()._config
 
     from tensorflow.python.client import device_lib
-    local_device_protos = device_lib.list_local_devices()
+    local_device_protos = device_lib.list_local_devices(session_config)
     return [x.name for x in local_device_protos if x.device_type == 'GPU']
 
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