How to Implement FlashAttention (Metal Port) on Apple Silicon

Jul 14, 2023 | Data Science

If you’re diving into the world of AI and looking to leverage the highly optimized FlashAttention algorithm on Apple silicon, you’re in the right place! In this blog post, we’ll guide you through the process of setting up and using the FlashAttention implementation tailored for Apple hardware. Let’s illuminate the path to effective AI computations!

Understanding FlashAttention: An Analogy

Imagine you’re trying to serve the best dishes at a restaurant (your AI model). Now, you have a kitchen (your processor) where various chefs (execution units) need to work efficiently to whip up meals (compute tasks). If the chefs can work without bumping into each other (parallelism) and use their tools (registers) wisely, they can serve the dishes faster (higher performance). However, if some ingredients are way too many and cramp the kitchen space (register pressure), they must find clever ways to manage their space without losing efficiency. This balance of efficiency, management, and speed is what the FlashAttention algorithm achieves.

Setting Up FlashAttention

To get started using FlashAttention, follow these steps to set up your workflow:

  • Download the Swift package for FlashAttention.
  • Open your terminal and clone the repository using the command:
    git clone https://github.com/philipturner/metal-flash-attention
  • Compile with the optimization flag:
    swift build -Xswiftc -Ounchecked
  • Ensure it compiles by running:
    swift test -Xswiftc -Ounchecked
  • For Xcode, double-click on Package.swift to open the project and check the hierarchy.

Editing and Customizing Source Code

Once you have the foundation ready, you might want to dive deeper into customization:

  • Locate the multi-line string literals in:
    • Sources/FlashAttention/Attention/AttentionKernel
    • Sources/FlashAttention/GEMM/GEMMKernel
  • Add random text to one of the literals. If the Metal compiler throws an error, that means your changes are being registered.
  • Start exploring features like block sparsity by integrating or translating the raw source code into your existing applications!

Troubleshooting

If you encounter challenges during setup or execution, here are some troubleshooting tips:

  • Ensure you’re compiling with the -Xswiftc -Ounchecked flag to avoid performance issues.
  • Double-check the paths when locating source files, as an incorrect path could lead to build failures.
  • If you don’t see errors with your test changes, validate that you’re modifying the correct files and lines.
  • Consult the documentation in the repository for any recent updates or issues that may relate to your setup.

For more insights, updates, or to collaborate on AI development projects, stay connected with fxis.ai.

Performance Measurement

Finally, it’s crucial to quantify the performance of your implementations:

  • Understand your performance in gigainstructions per second (GINSTRs) rather than gigaflops (GFLOPS) to better reflect your algorithm’s efficiency.
  • Use roofline models to visualize the performance landscape of your implementation versus the official FlashAttention repository.

At fxis.ai, we believe that such advancements are crucial for the future of AI, as they enable more comprehensive and effective solutions. Our team is continually exploring new methodologies to push the envelope in artificial intelligence, ensuring that our clients benefit from the latest technological innovations.

Conclusion

By following the steps laid out above, you can successfully set up and utilize FlashAttention within your applications on Apple silicon. Remember, the performance of your implementation is as important as its correctness, so invest time in optimizing your workloads.

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