Fix missing `restore_collection` in tower. (fix #462)

tensorpack/graph_builder/predict.py

 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
-# File: predictor_factory.py
+# File: predict.py
 
 import tensorflow as tf
 from contextlib import contextmanager

tensorpack/input_source/input_source.py

@@ -87,7 +87,8 @@ class FeedInput(InputSource):
         return self.ds.size()
 
     def _setup(self, inputs):
-        self._all_placehdrs = [v.build_placeholder(prefix='') for v in inputs]
+        # placeholders as input are always safe to reuse.
+        self._all_placehdrs = [v.build_placeholder_reuse() for v in inputs]
         self._cb = self._FeedCallback(self._iter_ds, self._all_placehdrs)
 
     def _get_input_tensors(self):

tensorpack/tfutils/collection.py

@@ -150,6 +150,7 @@ class CollectionGuard(object):
                     self._name, ', '.join(
                         map(lambda t: "({}: {}->{})".format(*t),
                             size_change))))
+        restore_collection(self._freeze_backup)
 
     def get_collection_in_tower(self, key):
         """