problem with AI not detecting GPU

[mapepe18]

Hello there. I was trying the AI extension on my windows machine. I followed the steps here: https://itksnap-dls.readthedocs.io/en/latest/quick_start.html#troubleshooting

I tried with a remote connection to colab and everything worked fine. But when running locally the system does not detect my nvidia gpu and set to use cpu. I have tried in 2 different computers, one with windows 11 with a RTX 3070 ti and another with windows 10 with rtx 3090. In both it happened and of course if trying to run with cpu itk-snap freezes when trying to do anything.

The itk installation file was the itksnap-4.4.0-alpha4-20250730-win64-AMD64.exe

Here a screenshot of one of the computers:

The text is in spanish but you can clearly see the 'gpu not available' message.

Thanks in advance

[pyushkevich]

Hi!

Thank you for reporting this bug. I think the problem has to do with the combination of PyTorch and CUDA python package versions, as I can tell from this post: https://stackoverflow.com/questions/57238344/i-have-a-gpu-and-cuda-installed-in-windows-10-but-pytorchs-torch-cuda-is-availa

I think to get it to work, you will need to create your Python virtual environment manually. Create the virtual environment using

python3 -m venv /path/to/virtual_env
source /path/to/virtual_env/bin/activate

Follow CUDA and Torch installation instructions from PyTorch website: https://pytorch.org/get-started/locally/

Install itksnap_dls

pip install itksnap_dls

Then you should be able to point ITK-SNAP to this virtual environment.

Please let me know if this workaround works

Thanks!
Paul

[mapepe18]

Hello again!
Yes @pyushkevich that did the trick, however a couple of things I'll will mention if anyone gits into the problem.

I first installed the torch installtion with cuda. Afterwards I installed the itksnap_dls, the itksnap_dls I think deleted and reinstalled the torch versions I had, as they changed and at that point I still had the same problem. So after installing itksnap_dls I reinstalled the torch version I wanted and then it worked.

Problem is very likely related to the requirements within itksnap_dls.

So the steps that worled for me:

1 Create the virtualenv
2 Install itksnap_dls
3 Install torch (version might depend on yur gpu), with my torch==2.7.1+cu118, torchvision==0.22.1+cu118 with my laptop 3070 ti

Thanks again