Theano/Theano — pull request #1084 by goodfeli (2012-11-20 15:14:15+00:00)
Title: Fix disconnected input bug

Fixes a bug where disconnected inputs may not raise an exception. The value of the gradient is still computed correctly. Adds a unit test to catch this bug. Adds a specific exception for disconnected inputs, so that this mechanism can be explicitly unit tested.