adding comment for multiple -1 values

theano/tensor/basic.py

@@ -4425,7 +4425,9 @@ class Reshape(Op):
             new_dims = [node.inputs[1][i] for i in xrange(self.ndim)]
             # since new_dims has one negative value (-1), the
             # multiplication of all values should be negated
-            # to give a positive value
+            # to give a positive value.
+            # To avoid optimization complexity, we avoid checking
+            # for the case when there are two or more '-1' values.
             return [tuple([switch(eq(new_dims[i], -1),
                                   theano.tensor.mul(*ishapes[0]) //
                                   (-theano.tensor.mul(*new_dims)),