[RFC] cross-platform: Refactoring bitsandbytes/cuda_setup

[Titus-von-Koeller]

Summary

This RFC aims to discuss and gather community input on refactoring the bitsandbytes/cuda_setup module. The goal is to enhance its functionality, simplify the user experience across different hardware and operating systems, and prepare it for upcoming device support expansions.

Background

bitsandbytes has become instrumental in democratizing AI, thanks to its deep integration with hardware. Despite millions of monthly downloads, a fraction of users encounter issues, such as those detailed in #914. Our objective is to make bitsandbytes as easily usable (e.g. as easy as pip install bitsandbytes and load_in_4bit=True ) as possible while mostly hiding the complexities of the software-hardware boundary under the hood, maintaining the ease of installation and use, while improving error reporting and handling.

Current Challenges

Setup Module Issues

• Bug Reports from python -m bitsandbytes: This feature, intended to simplify debugging, sometimes presents similar tracebacks for different underlying issues, causing confusion in the issue threads.
• CUDA Install and Environment Challenges: Many problems arise not from bitsandbytes itself, but from user-side issues with CUDA installations, environment settings (e.g. LD_LIBRARY_PATH), or hardware configurations.
• Perceived Reliability: There are some issues with the setup code that need be fixed. The code quality could be much better.

Diverse Hardware Landscape

• GPU-Nvidia Variability: Different generations and capabilities (e.g., Compute Capability, tensor cores, data types).
• Emerging GPU-AMD Support: Efforts like PR #756 are in progress to integrate AMD hardware.
• Apple Silicon Requests: Interest shown in PR #257 and other contributions.
• Intel GPU+CPU Quantization: The initiative by Intel with PR #898 for device abstraction.

Operating System Variability

• Linux as Primary OS: Continued focus on Linux support.
• Windows and Apple Support: Evaluating and integrating community contributions for broader OS support:
  • Windows: Limited support atm, but high impact - need to evaluate the status quo, community contributions and come up with a roadmap
  • Apple: Currently, no support - Ongoing discussions, community contributions that weren't accepted so far and quite a high interest - need to further evaluate the status quo, community contributions and come up with a roadmap.

Proposed Improvements

1. Refactoring cuda_setup: Enhancing code quality and clarity to better handle the diverse hardware and OS scenarios.
2. Error Reporting Enhancement: Develop a more nuanced error reporting mechanism that reflects the source of issues as accurate as possible, while making the conflation of issues harder by providing distinct traces.
3. Community Engagement: Actively seeking community input, especially for cross-platform compatibility and new device support.
4. CI/CD Strategies: Discussing and implementing robust CI/CD processes to facilitate testing across various platforms and hardware.

Call to Action

We invite the community to provide feedback and suggestions on the following:

• Improvements to the cuda_setup module.
• Strategies for handling diverse hardware and operating systems.
• Ideas for an effective CI/CD setup - we'll provide a separate RFC for that, but feel free to mention initial thoughts here as well.
• Any other relevant insights or experiences.

Timeline and Milestones

We'll take an incremental take on improving the setup module. The more actionable and commonly agreed, the quicker we can implement.

Contribution and Feedback Mechanism

Please share your thoughts, suggestions, and feedback in the thread below.

Summary and Next Steps

This RFC serves as a starting point to get feedback and coordinate the collaborative effort to refine bitsandbytes's setup process. We aim to address the current challenges, embrace the diversity of hardware and operating systems, and build a robust, user-friendly setup. Your participation in this process is crucial, and we look forward to your valuable input.

[wkpark]

See also PR #873 (merged), PR #876 for windows and PR #908

[jgong5]

CPU Quantization: The initiative by Intel with #898 for device abstraction.

Hey, one thing to clarify. The device abstraction proposed in #894 and the PR #898 are not only about CPU quantization but also for Intel GPU. Therefore, we tried to abstract out the interfaces that the backend needs to implement and also provided a registration mechanism for supporting new devices.

[younesbelkada]

Hi @jgong5 @wkpark
Are you connected through slack to discuss more details about bnb refactor and iterate quickly on this? Can I use your emails to send Slack invites?

[TAJD]

This is really exciting!

Ideas for an effective CI/CD setup - we'll provide a separate RFC for that, but feel free to mention initial thoughts here as well.

GPU runners now appear to be available on GitHub Actions and I can't think of a more useful project to begin trialling their usage.

There is a lot of complexity regarding the number of different CUDA versions, hardware and other dependencies. For now one goal could be to get the test suite automated and running cleanly for a limited combination of CUDA versions/hardwares and then building out the build/deployment process from there.

[rickardp]

Nice to see some initiative on this again. Here's a few points from me.

1. Blessing of the maintainer(s) that this is a truly portable library, and not just a CUDA library that can be made to run some MPS kernels with some effort. The alternative is to maintain a fork. This comment M1.M2 MacOS Users #485 (comment) seems to have indicated so, but it seems to have since died out. @Titus-von-Koeller do I understand you have interest in driving these changes to be mainlined in this repo?
2. See my comment here M1.M2 MacOS Users #485 (comment). Mainly, build in CMake, focus on getting everything to build on GitHub actions, test coverage. Get feature parity on CPU to be able to have test coverage on all hardware. Specifically, it would be possibly to make this library very easy to use ("pip install bitsandbytes") with binary wheels for all supported platforms (with some tradeoff in packaging multiple CUDA kernels for different supported CUDA versions).
   2b) As OP indicated, CUDA setup code is quirky. I think it tries to solve some edge cases better solved by following standard installation processes (look att PyTorch). But I am no expert. In any case, I think this library should focus on the kernels and leave CUDA setup to other frameworks/libraries.
3. Then port kernel by kernel to hardware like MPS or Intel. Remember that contributors to these codebases will not be able to run CUDA kernels typically, so test coverage will be a challenge. And vice versa. Possibly the range of GitHub agents are now sufficient as indicated by @TAJD 's comment

As for some of the details / tech choices on portability, please see prior discussion in #252 and #485 as there was a lot of good discussions already.

@Titus-von-Koeller I understand that this issue might be specific to the cuda_setup, but I think that if the decision is made to build true binary wheels (see bullet 2/2b above), a lot of the complexity of the CUDA set up goes away. So my proposal would be start by agreeing that this library will be distributed this way, and load the CUDA kernels for the CUDA runtime supplied by PyTorch (querying PyTorch for the details, IIRC this is possibly but my knowledge here is 6 months old so I might be wrong here).

I'm happy to spend some time reviving/rebasing/refactoring any of the work on PR #257 that are of interest to the community, but I would like to get some commit from a maintainer that this actually has a chance of getting merged so it's not just a dead end.