Fix bug in legacy NN updateGradParameters (pytorch#714)

Author: adamlerer

test/test_legacy_nn.py

@@ -1154,6 +1154,15 @@ def test_NarrowTable(self):
         module.__repr__()
         str(module)
 
+    def test_accUpdateGradParameters(self):
+        module = nn.LookupTable(5, 3)
+        module.weight.fill_(2)
+        input = torch.LongTensor([1, 3])
+        output = module.updateOutput(input)
+        module.backwardUpdate(input, output, 0.1)
+        self.assertEqual(module.weight[0, 0], 2)
+        self.assertEqual(module.weight[3, 0], 1.8)
+
     def _build_net(self):
         return (nn.Sequential()
                 .add(nn.Concat(0)

torch/legacy/nn/Module.py

@@ -49,13 +49,19 @@ def accGradParameters(self, input, gradOutput, scale=1):
         pass
 
     def accUpdateGradParameters(self, input, gradOutput, lr):
-        gradWeight = self.gradWeight
-        gradBias = self.gradBias
-        self.gradWeight = self.weight
-        self.gradBias = self.bias
+        has_weight = hasattr(self, 'weight') and self.weight is not None
+        has_bias = hasattr(self, 'bias') and self.bias is not None
+        if has_weight:
+            gradWeight = self.gradWeight
+            self.gradWeight = self.weight
+        if has_bias:
+            gradBias = self.gradBias
+            self.gradBias = self.bias
         self.accGradParameters(input, gradOutput, -lr)
-        self.gradWeight = gradWeight
-        self.gradBias = gradBias
+        if has_weight:
+            self.gradWeight = gradWeight
+        if has_bias:
+            self.gradBias = gradBias
 
     def sharedAccUpdateGradParameters(self, input, gradOutput, lr):
         if self.parameters():