[RFC] Cross-Platform Refactor: CPU-only implementation

[rickardp]

Motivation

As we want to have this library portable, the first step would be to make 100% of this library run correctly on only CPU (i.e. not requiring CUDA for any part of the functionality). This would serve two purposes:

• Provide a baseline that contributors of ports can reference
• Provide a fallback for partially implemented hardware platforms

Proposed solution

• [ ] Implement all the CUDA kernels in "normal" C++
• [ ] Make sure the unit tests all run on the CPU as well
• [ ] Make sure unit test coverage is satisfactory

Open questions

• Which CPU architectures do we support (x86_64 and arm64 are givens, but any more)?
• How do we deal with SIMD intrinsics? Build separate libraries for each SIMD architecture? Or run-time selection based on CPU features?

@Titus-von-Koeller Feel free to edit this issue as you see fit, if you want a different structure for it for example.tbd

tbd

[simepy]

@rickardp Where are we on this feature ? It is some part already working, or another threads talking about this feature ?, not much comment here.

I'm especially interested about arm64 CPU only

[rickardp]

@rickardp Where are we on this feature ? It is some part already working, or another threads talking about this feature ?, not much comment here.

Hi @simepy, sorry not much to add here still. I am still up for contributing towards this when 1) I have time to do so and 2) the dependencies that I do not have time to contribute are ready to use. More specifically the idea is to take a gradual approach and use the reference implementation where MPS acceleration is not yet implemented. Currently, large parts of this codebase require CUDA, which does not run on Apple silicon, making a partial implementation virtually unusable.