Merge pull request #957 from goodfeli/fix_elemwise_grad

theano/scalar/basic.py

@@ -843,7 +843,11 @@ class LogicalComparison(BinaryScalarOp):
         return [int8]
 
     def grad(self, inputs, output_gradients):
-        return [None, None]
+        x, y = inputs
+        out = self(x, y)
+        assert str(out.type.dtype).find('int') != -1
+        return [x.zeros_like().astype(theano.config.floatX),
+                y.zeros_like().astype(theano.config.floatX)]
 
 
 class FixedLogicalComparison(UnaryScalarOp):
@@ -854,7 +858,10 @@ class FixedLogicalComparison(UnaryScalarOp):
         return [int8]
 
     def grad(self, inputs, output_gradients):
-        return [None]
+        x ,= inputs
+        out = self(x)
+        assert str(out.type.dtype).find('int') != -1
+        return [x.zeros_like().astype(theano.config.floatX)]
 
 
 class LT(LogicalComparison):

theano/scalar/tests/test_basic.py

@@ -207,6 +207,13 @@ class test_div(unittest.TestCase):
         assert isinstance((f/c).owner.op, TrueDiv)
         assert isinstance((a/c).owner.op, TrueDiv)
 
+def test_grad_gt():
+    x = float32(name = 'x')
+    y = float32(name = 'y')
+    z = x > y
+    g = theano.gradient.grad(z, y)
+    assert g.eval({ y : 1. }) == 0.
+
 
 # Testing of Composite is done in tensor/tests/test_opt.py
 # in test_fusion, TestCompositeCodegen

theano/tensor/elemwise.py

@@ -690,6 +690,8 @@ class Elemwise(Op):
             scalar_ograds = [Scalar(dtype=ograd.type.dtype)()
                     for ograd in ograds]
             scalar_igrads = self.scalar_op.grad(scalar_inputs, scalar_ograds)
+            for igrad in scalar_igrads:
+                assert igrad is not None
 
         finally: