How to make a cuda available using CUDA_VISIBLE_DEVICES?

What I’d like to do is

import os, torch

print(torch.cuda.is_available())  # True

print(torch.cuda.is_available())  # False

print(torch.cuda.is_available())  # True

But os.environ["CUDA_VISIBLE_DEVICES"]="" does not make cuda available again. How can I do that?

Hi :slight_smile:

I use:

  • os.environ[“CUDA_VISIBLE_DEVICES”]="" to switch to cpu mode
  • os.environ[“CUDA_VISIBLE_DEVICES”]=“0” to cuda mode, if I have only 1 GPU
  • os.environ[“CUDA_VISIBLE_DEVICES”]=“0,2,5” to use only special devices (note, that in this case, pytorch will count all available devices as 0,1,2 )

Setting these environment variables inside a script might be a bit dangerous and I would also recommend to set them before importing anything CUDA related (e.g. PyTorch).

It looks as if you would like to mask the GPU dynamically inside your script.
If that’s the case, I would rather use the device variable and write device-agnostic code than rely on CUDA_VISIBLE_DEVICES.


Thank you for the great response!

You are right, I hide devices, for example, to show tensorboard, then all GPUs are used (via export CUDA_VISIBLE_DEVICES="" in a console)

…I never fought about consequences of dynamic masking in the code, because didn’t have problems. Thanks