fix for random states

we should have as initial value for some parameter 0, unless it is a random state, case in which is not differentiable and should be None

fix for random states
7b5838d7 · Razvan Pascanu · c37e8c25 · 7b5838d7
--- a/theano/gradient.py
+++ b/theano/gradient.py
@@ -289,7 +289,12 @@ def Rop(f, wrt, eval_points):
                if inp in wrt:
                    local_eval_points.append(eval_points[wrt.index(inp)])
                elif inp.owner is None:
-                    local_eval_points.append(inp.zeros_like())
+                    try:
+                        local_eval_points.append(inp.zeros_like())
+                    except:
+                        # None should be used for non-differentiable
+                        # arguments, like for example random states
+                        local_eval_points.append(None)
                elif inp.owner in seen_nodes:
                    local_eval_points.append(