Need the ability to set a smaller batch size for image classifier & image similarity

[srikris]

The feature extractor used image classifier and image similarity sets the batch size to 512 and we should expose that parameter all the way up to the image classifier and image similarity.

[gustavla]

If we do this, it would be good to expose this for object detection too to allow low-memory GPUs. However, it is harder since it doesn't use a stopping criterion based on a validation set and instead a heuristic to set the number of iterations. This heuristic would get more complicated.

[TobyRoseman]

This is fixed in beta 1 of version 5.0