Speed up add to fgraph when there is many clients to nodes

theano/gof/fg.py

@@ -260,7 +260,7 @@ class FunctionGraph(utils.object2):
         """
         return r.clients
 
-    def __add_clients__(self, r, new_clients):
+    def __add_client__(self, r, new_client, check=True):
         """
         Updates the list of clients of r with new_clients.
 
@@ -268,18 +268,19 @@ class FunctionGraph(utils.object2):
         ----------
         r
             Variable.
-        new_clients
-            List of (node, i) pairs such that node.inputs[i] is r.
+        new_client
+            (node, i) pairs such that node.inputs[i] is r.
 
         """
-        if set(r.clients).intersection(set(new_clients)):
+        test = new_client in r.clients
+        if test:
             print('ERROR: clients intersect!', file=sys.stderr)
             print('  RCLIENTS of', r, [(n, i, type(n), id(n))
                                        for n, i in r.clients], file=sys.stderr)
             print('  NCLIENTS of', r, [(n, i, type(n), id(n))
-                                       for n, i in new_clients], file=sys.stderr)
-        assert not set(r.clients).intersection(set(new_clients))
-        r.clients += new_clients
+                                       for n, i in [new_client]], file=sys.stderr)
+        assert not test
+        r.clients.append(new_client)
 
     def __remove_clients__(self, r, clients_to_remove,
                            prune=True, reason=None):
@@ -431,7 +432,7 @@ class FunctionGraph(utils.object2):
                 if input not in self.variables:
                     self.__setup_r__(input)
                     self.variables.add(input)
-                self.__add_clients__(input, [(node, i)])
+                self.__add_client__(input, (node, i))
             assert node.fgraph is self
             self.execute_callbacks('on_import', node, reason)
 
@@ -470,7 +471,7 @@ class FunctionGraph(utils.object2):
             return
 
         self.__import_r__(new_r, reason=reason)
-        self.__add_clients__(new_r, [(node, i)])
+        self.__add_client__(new_r, (node, i))
         prune = self.__remove_clients__(r, [(node, i)], False)
         # Precondition: the substitution is semantically valid
         # However it may introduce cycles to the graph,  in which case the