alchemiops.py: Flag as unavailable on non-NVIDIA torch builds

[yantar92]

Summary

On ROCm builds, nvalchemiops correctly imports but does not work during runtime, yielding

File "<...>/lib/python3.12/site-packages/torch_sim/neighbors/init.py", line 86, in torchsim_nl
return alchemiops_nl_n2(
^^^^^^^^^^^^^^^^^
File "<...>/lib/python3.12/site-packages/torch_sim/neighbors/alchemiops.py", line 62, in alchemiops_nl_n2
res = _batch_naive_neighbor_list(
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "<...>/lib/python3.12/site-packages/nvalchemiops/torch/neighbors/batch_naive.py", line 1513, in batch_naive_neighbor_list
compute_naive_num_shifts(cell, cutoff, pbc)
File "<...>/lib/python3.12/site-packages/nvalchemiops/torch/neighbors/neighbor_utils.py", line 326, in compute_naive_num_shifts
wp_device = wp.device_from_torch(device)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "<...>/lib/python3.12/site-packages/warp/_src/torch.py", line 39, in device_from_torch
return warp._src.context.runtime.cuda_devices[torch_device.index]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^
IndexError: list index out of range

Checklist

Before a pull request can be merged, the following items must be checked:

• Doc strings have been added in the Google docstring format, but not in _import_nvalchemiops_batch_neighbors, which I did not touch.
• Run ruff on your code. (no new failures)
• Tests have been added for any new functionality or bug fixes.

[CompRhys]

Thanks for the contribution, I totally understand the issue but I am not sure this is the right fix because on CPU achemiops should be the default so the check needs to check if there is a non-cuda accelerator not just if there is not a cuda accelerator.

[yantar92]

Oops. Did not realize that alchemiops works on CPUs. I have updated the commit.

[lil-lon]

Btw, if you want to detect ROCm, you can use torch.version.hip variable.

[yantar92]

Btw, if you want to detect ROCm, you can use torch.version.hip variable.

I have considered it, but AFAIU alchemiops will fail on any GPU that is not CUDA.