Wasm SIMD support

[ulan]

Wasm SIMD is a stable feature that is supported by many Wasm runtimes. It is available in Rust in core::arch::wasm32.

I have two questions to the maintainers:

1. Do you have plans to implement Wasm SIMD support?
2. Would you accept an external contribution that implements support for Wasm SIMD?

[kali]

1. this is not an active topic for us
2. yes

[ulan]

Would you accept an external contribution that implements support for Wasm SIMD?
yes

Great, thanks! I am learning the source code of tract and my current understanding is to add linalg/wasm and follow one of the existing SIMD implementations. Do you have any suggestions or thing to look out for when implementing?

How would you approach this on the high-level if you were to implement Wasm SIMD?

[kali]

You should try to produce a square-ish mat * mul (m=n) implementation, and also a mat * vec (n=1).

You should be able leverage the tests available for the others products. Start implementing return_zero, return_c, the add/mul by row and cols: these are the one that will cover the load and store functions. Do the actual dot product at the end.

Have fun! And feel free to ask any question.

[kali]

Depending on your familiarity of efficient mat mul implemetation, you may want to check out the sonos tech blog articles (https://tech-blog.sonos.com/posts/the-anatomy-of-efficient-matrix-multipliers/ and part 3).

For tile sizes, I would probably start with 8x8 (easy to map to aarch64 and intel) and 32x1 for mat vec.

[ulan]

Thank you for the pointers @kali!