Keras with Tensorflow backend - Run predict on CPU but fit on GPU

Question

I am using keras-rl to train my network with the D-DQN algorithm. I am running my training on the GPU with the model.fit_generator() function to allow data to be sent to the GPU while it is doing backprops. I suspect the generation of data to be too slow compared to the speed of processing data by the GPU.

In the generation of data, as instructed in the D-DQN algorithm, I must first predict Q-values with my models and then use these values for the backpropagation. And if the GPU is used to run these predictions, it means that they are breaking the flow of my data (I want backprops to run as often as possible).

Is there a way I can specify on which device to run specific operations? In a way that I could run the predictions on the CPU and the backprops on the GPU.

Answer 1

Maybe you can save the model at the end of the training. Then start another python file and write os.environ["CUDA_VISIBLE_DEVICES"]="-1"before you import any keras or tensorflow stuff. Now you should be able to load the model and make predictions with your CPU.