[WIP] 2849 Add cupy install as optional package

[Nic-Ma]

Fixes #2849 .

Description

This PR added all the necessary info for cupy package.

Status

Work in progress

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).
• Breaking change (fix or new feature that would cause existing functionality to change).
• New tests added to cover the changes.
• Integration tests passed locally by running ./runtests.sh -f -u --net --coverage.
• Quick tests passed locally by running ./runtests.sh --quick --unittests.
• In-line docstrings updated.
• Documentation updated, tested make html command in the docs/ folder.

[Nic-Ma]

Hi @wyli ,

Seems we need to specify the CUDA version when installing cupy from wheel:
https://docs.cupy.dev/en/stable/install.html#installing-cupy
We can manually install cupy with specific CUDA version in CI config, but I am not clear how to support optional install with CUDA version?

Thanks.

[wyli]

we had discussions in #2131 as well, it's currently not resolved

[Nic-Ma]

OK, I see.
@rijobro , I think we don't have a solution so far?

Thanks.

[rijobro]

Thanks for linking the previous PR. So do any of our testing environments install cupy? Just want to confirm that we test our cupy code.