Overly rigid

[brandondube]

As-is, the user has to specify "beta" (or 10**beta, anyway) up-front and can't change it. That means they have to make a new EFC class, which may have some overhead. For example, we could store Vt and U and not compute them again, it is just a different S_inv = ....

Something ~=

class EFC:
   def update_beta(self, b):
        pass

would be nice to have

As well, the selection of pixels for the dark hole happens during the jacobian calculation step. Building that matrix is very costly (comparatively), so we should keep all of the pixels and move the dark hole mask into EFC or other controllers, and allow the user to change it later.

The same goes for the G -> G2 nonsense; the user shouldn't have to do it; it should go inside the EFC class' inner workings.