Add a case to local_neg_div_neg

theano/tensor/opt.py

@@ -932,8 +932,11 @@ def local_neg_neg(node):
 @register_specialize
 @gof.local_optimizer([T.neg])
 def local_neg_div_neg(node):
+    """- (-a / b) -> a / b
+
+    Also performs - (c / b) -> ((-c) / b) when c is a scalar constant.
+    """
     if node.op == T.neg:
-        """- (-a / b) -> a / b"""
         if node.inputs[0].owner and node.inputs[0].owner.op == T.true_div:
             frac = node.inputs[0]
             num, denom = frac.owner.inputs
@@ -942,6 +945,11 @@ def local_neg_div_neg(node):
                     # No other clients of the original division
                     new_num = num.owner.inputs[0]
                     return [T.true_div(new_num, denom)]
+            elif numpy.all(num.broadcastable) and isinstance(num, gof.Constant):
+                if len(frac.clients) == 1:
+                    new_num = -num.data
+                    return [T.true_div(new_num, denom)]
+
 
 @gof.local_optimizer([T.mul])
 def local_mul_zero(node):