Running test net on a separate device id

[ishan193]

Hi,
I am trying to find a way to separate out my test net and use a specific gpu id for all test related stuff. The need occurred because sometimes the testing at a specific interval during training is impossible if the net is very big. If we don't allocate the diff and data on one particular device (gpu), then we can just use if for forward prop during testing.
Currently the solver initializes the test net and if I hack there and set a particular device id, then the NCCL is not able to use the remaining gpus for multi-gpu training properly.

Any advice or quick hack?