TargetDevice -> "GPU" works for old macbooks that have GEForce GT 750m cards (like mine), but what about other nvidia cards?
Does it (or will it) work with opencl based graphics card types?
All NVIDIA GPUs except newest 10xx.
"A number of TensorFlow users are reporting problems using a 1080/1070 with CUDA v7.5 and cuDNN v5.0 (which we are currently using for 11.0)."
"So it looks like you will need to wait for 11.1, which will definitely support CUDA 8.0."
OpenCL is in plans.
Mathematica's neural network functionality is based on MXNET. Wolfram developers are contributing to this project very actively.