Merge pull request #6629 from abergeron/subtensor_grad

theano/tensor/subtensor.py

@@ -1761,7 +1761,14 @@ class AdvancedSubtensor1(Op):
             rval1 = [sparse_module_ref.construct_sparse_from_list(x, gz,
                                                                   ilist)]
         else:
-            rval1 = [advanced_inc_subtensor1(x.zeros_like(), gz, ilist)]
+            if x.dtype in theano.tensor.discrete_dtypes:
+                # The output dtype is the same as x
+                gx = x.zeros_like(dtype=theano.config.floatX)
+            elif x.dtype in theano.tensor.complex_dtypes:
+                raise NotImplementedError("No support for complex grad yet")
+            else:
+                gx = x.zeros_like()
+            rval1 = [advanced_inc_subtensor1(gx, gz, ilist)]
         return rval1 + [DisconnectedType()()] * (len(inputs) - 1)
 
     def R_op(self, inputs, eval_points):
@@ -2238,9 +2245,15 @@ class AdvancedSubtensor(BaseAdvancedSubtensor):
     def grad(self, inputs, grads):
         gz, = grads
         x = inputs[0]
+        if x.dtype in theano.tensor.discrete_dtypes:
+            # The output dtype is the same as x
+            gx = x.zeros_like(dtype=theano.config.floatX)
+        elif x.dtype in theano.tensor.complex_dtypes:
+            raise NotImplementedError("No support for complex grad yet")
+        else:
+            gx = x.zeros_like()
         rest = inputs[1:]
-        return [advanced_inc_subtensor(theano.tensor.zeros_like(x), gz,
-                                       *rest)] + \
+        return [advanced_inc_subtensor(gx, gz, *rest)] + \
             [DisconnectedType()()] * len(rest)
 advanced_subtensor = AdvancedSubtensor()
 
@@ -2258,9 +2271,15 @@ class AdvancedBooleanSubtensor(BaseAdvancedSubtensor):
     def grad(self, inputs, grads):
         gz, = grads
         x = inputs[0]
+        if x.dtype in theano.tensor.discrete_dtypes:
+            # The output dtype is the same as x
+            gx = x.zeros_like(dtype=theano.config.floatX)
+        elif x.dtype in theano.tensor.complex_dtypes:
+            raise NotImplementedError("No support for complex grad yet")
+        else:
+            gx = x.zeros_like()
         rest = inputs[1:]
-        return [advanced_boolean_inc_subtensor(theano.tensor.zeros_like(x), gz,
-                                               *rest)] + \
+        return [advanced_boolean_inc_subtensor(gx, gz, *rest)] + \
             [DisconnectedType()()] * len(rest)
 advanced_boolean_subtensor = AdvancedBooleanSubtensor()