Tensorflow not running on GPU

To check which devices are available to TensorFlow you can use this and see if the GPU cards are available:

from tensorflow.python.client import device_lib
print(device_lib.list_local_devices())

Edit Also, you should see this kind of logs if you use TensorFlow Cuda version :

I tensorflow/stream_executor/dso_loader.cc:128] successfully opened CUDA library libcublas.so.*.* locally
I tensorflow/stream_executor/dso_loader.cc:128] successfully opened CUDA library libcudnn.so.*.*  locally
I tensorflow/stream_executor/dso_loader.cc:128] successfully opened CUDA library libcufft.so.*.*  locally

I was still having trouble getting GPU support even after correctly installing tensorflow-gpu via pip. My problem was that I had installed tensorflow 1.5, and CUDA 9.1 (the default version Nvidia directs you to), whereas the precompiled tensorflow 1.5 works with CUDA versions <= 9.0. Here is download page on nvidia's site to get the correct CUDA 9.0:

https://developer.nvidia.com/cuda-90-download-archive

Also make sure to update your cuDNN to a version compatible with CUDA 9.0 https://developer.nvidia.com/cudnn https://developer.nvidia.com/rdp/cudnn-download

It may sound dumb, but try reboot. It helped me and some other folks in GitHub.