Merge pull request #1534 from lamblin/fix_disconnected_sum

theano/tensor/elemwise.py

@@ -693,7 +693,7 @@ class Elemwise(Op):
 
         #sum out the broadcasted dimensions
         for i, ipt in enumerate(inputs):
-            if rval[i] is None:
+            if isinstance(rval[i].type, (NullType, DisconnectedType)):
                 continue
 
             # list of all the dimensions that are broadcastable for input[i] so

theano/tensor/tests/test_elemwise.py

@@ -197,6 +197,14 @@ class test_Broadcast(unittest.TestCase):
         f(xv, yv)
         assert (xv == yv).all()
 
+    def test_fill_grad(self):
+        # Fix bug reported at
+        # https://groups.google.com/d/topic/theano-users/nQshB8gUA6k/discussion
+        x = TensorType(config.floatX, [0, 1, 0])('x')
+        y = TensorType(config.floatX, [0, 1, 0])('y')
+        e = tensor.second(x, y)
+        theano.grad(e.sum(), y)
+
     def test_weird_strides(self):
         if not theano.config.cxx:
             raise SkipTest("G++ not available, so we need to skip this test.")