made adding names optional

theano/gradient.py

@@ -328,7 +328,7 @@ def Lop(f, wrt, eval_points, consider_constant=None, warn_type=False,
 #########################
 
 def grad(cost, wrt, g_cost = None, consider_constant = None, warn_type = False,
-        disconnected_inputs = 'raise'):
+        disconnected_inputs = 'raise', add_names = True):
     """
     :type cost: Scalar (0-dimensional) Variable.
     :type wrt: Variable or list of Variables.
@@ -349,6 +349,11 @@ def grad(cost, wrt, g_cost = None, consider_constant = None, warn_type = False,
         - 'warn': consider the gradient zero, and print a warning.
         - 'raise': raise an exception.
 
+    :type add_names: bool
+    :param add_names: If True, variables generated by grad will be named
+        (d<cost.name>/d<wrt.name>) provided that both cost and wrt have
+        names
+
     :rtype: Variable or list/tuple of Variables (depending upon `wrt`)
 
     :return: symbolic expression of gradient of `cost` with respect to `wrt`.
@@ -426,9 +431,13 @@ def grad(cost, wrt, g_cost = None, consider_constant = None, warn_type = False,
                         "'ignore', 'warn' and 'raise'.")
             grad_dict[elem] = DisconnectedType()()
 
+    cost_name = None
+    if add_names:
+        cost_name = cost.name
+
     rval = _populate_grad_dict(var_to_node_to_idx,
             grad_dict, wrt, warn_type,
-            cost.name)
+            cost_name)
 
     for i in xrange(len(rval)):
         if isinstance(rval[i].type, DisconnectedType):