size limitation in FilterActs? about cuda-convnet HOT 3 OPEN

Hi James,

You're right, there is a maximum-grid-size-imposed limitation on the size of 
the convolution that can be performed in filterActs. I'm not really sure what 
to do about it yet, though. One hacky solution if you really need to perform 
such a big convolution is to split your filters into several sets, each set in 
its own matrix. Then call filterActs for each set. The target matrix can be the 
same for all calls (just a different offset into the same array). The gradient 
computation routines would have to be called twice too.

I'll probably come up with something better in the future but for now it's an 
unfixed bug. 

Alex

CUDA compute compatibility 2.x or lower has a limitation that x, y and z 
dimension of  a grid must be smaller than 65536. However when it comes to 3.x, 
x dimension of a grid can be as large as 2^31-1, which will be enough for 
larger pictures. The original function can be enhanced just by swapping x and y 
dimension. 

The suggested fix sounds very promising, Any plans to swap x and y in the 
future?