Sometimes running on device cuda and sometimes running on device cpu automatically, why? about torch

[icejean]

Well, it is my fault. Acutally every thing is O.K, both models are running on device cuda.
The cause is that, I'm running R torch on WSL2 Ubuntu22, and watching the GPU loads with Windows task manager, this leads to some misunderstanding.
The fact is that, CUDA toolkit on WSL2 Ubuntu is a special version that doesn't include Nvidia driver of Ubuntu，Windows will export the Windows Nvidia driver to Ubuntu at /usr/lib/wsl/lib/, and Windows task manager seems doesn't reflect all loads on the Nvidia GPU，especially those running on WSL2 Ubuntu. The main load in Windows task manaager of a Nvidia GPU is copy load, this isn't the fact.
And when I run nvidia-smi -l 1 on WSL2 Ubuntu, I can see the actual load on it, the GPU-Util & Compute M. indexes show that it's really running on the cuda device. May be nvidia-smi only looks for process running on Windows, not including those on WSL2 Ubuntu, it tells that 'No running processes found', but it isn't the truth.
The following is nvidia-smi output and windows task manager snapshot of the 1st model:

The folowing is the snapshot of the 2nd model:

After all, the fan of the GPU is running fast, it means tha the GPU is working hard.