Enabling GPU usage on Windows

To use your graphics card with CNTK on Windows, you need to have the latest GeForce or Quadro drivers for your graphics card (depending on which one you have). Aside from the latest drivers, you need to install the CUDA toolkit Version 9.0 for Windows.

You can download the CUDA toolkit from the NVIDIA website: https://developer.nvidia.com/cuda-90-download-archive?target_os=Windows&target_arch=x86_64. Once downloaded, run the installer and follow the instructions on the screen.

CNTK uses a layer on top of CUDA, called cuDNN, for neural-network-specific primitives. You can download the cuDNN binaries from the NVIDIA website at https://developer.nvidia.com/rdp/form/cudnn-download-survey. In contrast to the CUDA toolkit, you need to register an account to the website before you can download the cuDNN binaries. 

Not all cuDNN binaries work with every version of CUDA. The website mentions which version of cuDNN is compatible with which version of the CUDA toolkit. For CUDA 9.0, you need to download cuDNN 7.4.1. 

Once you have downloaded the cuDNN binaries, extract the zip file into the root folder of your CUDA toolkit installation. Typically, the CUDA toolkit is located at C:\program files\NVIDIA GPU Computing Toolkit\CUDA\v9.0.

The final step to enable GPU usage inside CNTK is to install the CNTK-GPU package. Open the Anaconda prompt in Windows and execute the following command:

pip install cntk-gpu