tensorflow: GPU device not found in Colab

My code worked well with GPU in Colab yesterday. But this morning it became very slow. So I suspect that CPU is used despite hardware accelerator is set to GPU in “change runtime type” explicitly. So I check the availability of GPU following the tutorial: https://colab.research.google.com/notebooks/gpu.ipynb

code chunk:

%tensorflow_version 2.x
import tensorflow as tf
device_name = tf.test.gpu_device_name()
if device_name != '/device:GPU:0':
  raise SystemError('GPU device not found')
print('Found GPU at: {}'.format(device_name))

Indeed, I got SystemError: GPU device not found. I tried this with different sessions or google user accounts, the same results. You should be able to replicate this in a new Colab session. Maybe some tensorflow updates are involved? It could be that Colab session provide GPU, but tensorflow can’t see it, e.g. tf.test.gpu_device_name() or tf.test.is_gpu_available(). Please help, thank you!