Implementation of Generalized Expectation Objective function for
an I.I.D. log-linear model. See Mann and McCallum, ACL 2008 for GE in CRFs.
This code, however, is just for log-linear model
IMPORTANT: the current implementation is only correct as long as
the labeled features passed to GE are binary.
However, other features are allowed to be real valued.
The original paper also discusses GE only for binary features.