[azakai]

I think you're rushing to judgement pretty quickly here. For example,

> 2. Identify proper use cases. The example are quite bogus currently. They show a mandelbrot.

That's just one tiny demo. See the github repo discussions for lots of debate on use cases,

https://github.com/johnmccutchan/ecmascript_simd/issues

This has been discussed very intensively, with input from people from Intel, Mozilla, and Google. Feel free to join in as well.

In general, while I sympathize to some extent with you and the Apple position here, you are fighting a strong trend in the industry. C has a SIMD API, C# has SIMD API, Dart has a SIMD API, etc. - all those were created for good reasons. Autovectorization would be great - hopefully Apple can prove it beats the API approach - but no compiler has proven it thus far, hence SIMD APIs in all those languages I mentioned.

[general_failure]

Thanks for the link! I tried going through the issues (randomly clicking) but I am not seeing use cases. https://github.com/johnmccutchan/ecmascript_simd/issues/89 https://github.com/johnmccutchan/ecmascript_simd/issues/85 https://github.com/johnmccutchan/ecmascript_simd/issues/84

They are good technical discussions. What I am looking for is use cases for people to use in websites.

[pcwalton]

Vertex skinning [1] (code at [2]) is a classic example. (This code is not vectorized, but it could easily be and is usually vectorized via intrinsics in games.) Any 3D game that wants to animate human characters over a long period of time is likely to be using this technique. Since we want games to run on the Web, of course, this is a use case for Web sites.

[1]: http://en.wikipedia.org/wiki/Skeletal_animation

[2]: https://github.com/h4writer/arewefastyet/blob/master/benchma...

[general_failure]

I am no expert on this but if games is the primary target, would it make sense to make some sort of vector(ization) API? Or some tesselator API.

It's honestly baffling that we keep away from threads in javascript but do all these optimizations like SIMD which are very minor. I mean practically every CPU out there has multiple cores. Workers don't cut it because they require copying data.

[pcwalton]

> I am no expert on this but if games is the primary target, would it make sense to make some sort of vector(ization) API? Or some tesselator API.

Both of those would be harder, and less general. Game developers are asking for SIMD; they aren't asking for specialized APIs.

> It's honestly baffling that we keep away from threads in javascript but do all these optimizations like SIMD which are very minor. I mean practically every CPU out there has multiple cores. Workers don't cut it because they require copying data.

Threads aren't easy to "just add" to JS. Making a thread-safe GC perform as well as today's highly-optimized single-threaded GCs is hard. And not even counting the engineering effort required, none of the millions of lines of JavaScript out there is thread-safe. Of course we will need a way to do threads eventually, but it's much harder than SIMD.

[anon1385]

>Making a thread-safe GC perform as well as today's highly-optimized single-threaded GCs is hard.

That is entirely a problem of your own making. You decided to bet hard on single threaded dynamic Javascript being a suitable model for all end user software. It turns out it isn't, but it's too late now.

This kind of thing is exactly why Javascript isn't a good choice as a general purpose VM platform. Which you are presumably aware of because you aren't writing the next generation of Firefox in Javascript, you are creating Rust. But apparently what isn't good enough for Mozilla is good enough for everybody else…

Which brings us to the real problem with the web - everybody except the browser vendors is a second class citizen.

[maccard]

Simd optimisations aren't very minor. For games anyway, we have a 90-10 rule (90% of time is spent inside 10% of the code) I'm sure that exists in other areas too. One of the most common operations performed is multiplying 4x4 matrices, which can get 300% speed ups with the correct simd operations. To get that speed up in the most called parts of your code is anything but minor

[azakai]

There are experiments with threads in JS, however that would be a much bigger change to the language than adding something like a SIMD API, so it is more controversial and takes longer to sort out.

[Narishma]

Skinning hasn't been done on the CPU for about a decade now. GPUs are much better at it.

[azakai]

There are lots of issues, can take a while to find all the use cases in them (work has been ongoing for some time). But from memory I can recall that

https://github.com/johnmccutchan/ecmascript_simd/issues/59

is interesting here, it mentions, among other things, the major SIMD-using code portion from an important real-world codebase (IMVU).

Might also be relevant discussion on the emscripten repo,

https://github.com/kripken/emscripten/issues?q=is%3Aopen+is%...

as some debate happened there while implementing code generation that emits SIMD.js.