This paper http://dl.acm.org/citation.cfm?id=2830854 http://dl.acm.org/citation.cfm?id=2830854 kind of has a solution to being more efficient. It has two networ

This paper http://dl.acm.org/citation.cfm?id=2830854 http://dl.acm.org/citation.cfm?id=2830854 kind of has a solution to being more efficient. It has two networks and uses the smaller one (more efficient) to infere first. If the result is accurate with high probability (the probability of one class is much larger than the probability of any other class) then there is no need to run the big (expensive) network.