Switching Keras backend Tensorflow to GPU I use Keras-Tensorflow combo installed with CPU option (it was said to be more robust), but now I'd like to try it with GPU-version. Is there a convenient way to switch? Or shall I re-install fully Tensorflow? Is the GPU version reliable?
I suggest reinstalling the GPU version of Tensorflow, although you can install both version of Tensorflow via virtualenv. GPU version of Tensorflow supports CPU computation, you can switch to CPU easily:

with device('/cpu:0'):
    # your code here


I have been using GPU version of Tensorflow on my Tesla K80 for a few months, it works like a charm. Feel free to have a try!