rewrite of local_mul_specialize

theano/tensor/opt.py

@@ -1353,42 +1353,49 @@ def local_mul_specialize(node):
         neg = False
         new_inputs = []
         for input in node.inputs:
+            # remove any neg arguments 
+            while input.owner and input.owner.op == T.neg:
+                neg ^= True
+                input = input.owner.inputs[0]
+
+            # remove special case arguments of 1, -1 or 0
             y = local_mul_canonizer.get_constant(input)
             if N.all(y == 1.0):
                 continue
             elif N.all(y == -1.0):
                 neg ^= True #toggles
             elif N.all(y == 0.0):
-                return fill_chain(input)
+                return [T.alloc(numpy.asarray(0, dtype=node.outputs[0].dtype),
+                        *node.env.shape_feature.shape_of[node.outputs[0]])]
             else:
                 new_inputs.append(input)
-        if len(new_inputs) < len(node.inputs):
-            if len(new_inputs) == 0:
-                if neg:
-                   newval = -y.flatten()[0]
+
+        if new_inputs != node.inputs:
+            if new_inputs:
+                if len(new_inputs) == 1:
+                    if neg:
+                        msg = -new_inputs[0]
+                    else:
+                        msg = new_inputs[0]
+                    return fill_chain(msg)
                 else:
-                   newval = y.flatten()[0]
-                #newval = -y.flatten()[0] if neg else y.flatten()[0]
-                return fill_chain(T.TensorConstant(T.TensorType(dtype=node.outputs[0].type.dtype,
-                    broadcastable = [True] * node.outputs[0].ndim), N.asarray(newval)))
+                    if neg:
+                        msg = -T.mul(*new_inputs)
+                    else:
+                        msg = T.mul(*new_inputs)
 
-            if len(new_inputs) == 1:
-              if neg:
-                msg = -new_inputs[0]
-              else:
-                msg = new_inputs[0]
-              return fill_chain(msg)
-              #  return fill_chain(-new_inputs[0] if neg else new_inputs[0])
+                return [T.alloc(T.cast(msg, node.outputs[0].dtype),
+                        *node.env.shape_feature.shape_of[node.outputs[0]])]
             else:
                 if neg:
-                  msg = -T.mul(*new_inputs)
+                    # return output's worth of -1
+                    return [T.alloc(numpy.asarray(-1, dtype=node.outputs[0].dtype),
+                            *node.env.shape_feature.shape_of[node.outputs[0]])]
                 else:
-                  msg = T.mul(*new_inputs)
+                    # return output's worth of 1
+                    return [T.alloc(numpy.asarray(1, dtype=node.outputs[0].dtype),
+                            *node.env.shape_feature.shape_of[node.outputs[0]])]
 
-                #return fill_chain(-T.mul(*new_inputs) if neg else \
-                #        T.mul(*new_inputs))
-    else:
-        return False
 register_specialize(local_mul_specialize)
 
 @gof.local_optimizer([T.add])