initial commit

theano/gof/fg.py

@@ -153,6 +153,7 @@ class FunctionGraph(utils.object2):
 
         self.inputs = list(inputs)
         self.outputs = outputs
+        self._removed_nodes = set()
 
         for f in features:
             self.attach_feature(f)
@@ -320,10 +321,12 @@ class FunctionGraph(utils.object2):
                               if output.clients or output in self.outputs]
             # If the apply node is not used and is not an output
             if not used_or_output:
+                if apply_node in self.apply_nodes:
+                    #keeping track of removed apply node
                     self.apply_nodes.remove(apply_node)
                     self.variables.difference_update(apply_node.outputs)
                     self.execute_callbacks('on_prune', apply_node, reason)
-
+                    self._removed_nodes.add(apply_node)
                     for i, input in enumerate(apply_node.inputs):
                         self.__remove_clients__(input, [(apply_node, i)],
                                                 reason=reason)
@@ -478,6 +481,12 @@ class FunctionGraph(utils.object2):
 
         for node in new_nodes:
             assert node not in self.apply_nodes
+            prevent_addition = False
+            for n in self._removed_nodes :
+                if node is n :
+                    prevent_addition = True
+                    
+            if not prevent_addition : 
                 self.__setup_node__(node)
                 self.apply_nodes.add(node)
             for output in node.outputs:
@@ -488,6 +497,7 @@ class FunctionGraph(utils.object2):
                     self.__setup_r__(input)
                     self.variables.add(input)
                 self.__add_clients__(input, [(node, i)])
+            if not prevent_addition :
                 assert node.fgraph is self
                 self.execute_callbacks('on_import', node, reason)