We rewrote our Rust WASM Parser in TypeScript – and it got 3x Faster

https://www.openui.com/blog/rust-wasm-parser

49•zahlekhan•1h ago

Comments

blundergoat•1h ago

The real win here isn't TS over Rust, it's the O(N²) -> O(N) streaming fix via statement-level caching. That's a 3.3x improvement on its own, independent of language choice. The WASM boundary elimination is 2-4x, but the algorithmic fix is what actually matters for user-perceived latency during streaming. Title undersells the more interesting engineering imo.

shmerl•1h ago

More like a misleading clickbait.

sroussey•57m ago

Yeah, though the n^2 is overstating things.

One thing I noticed was that they time each call and then use a median. Sigh. In a browser. :/ With timing attack defenses build into the JS engine.

Aurornis•55m ago

> Title undersells the more interesting engineering imo.

Thanks for cutting through the clickbait. The post is interesting, but I'm so tired of being unnecessarily clickbaited into reading articles.

socalgal2•45m ago

same for uv but no one takes that message. They just think "rust rulez!" and ignore that all of uv's benefits are algo, not lang.

estebank•30m ago

Some architectures are made easier by the choice of implementation language.

dmix•1h ago

That blog post design is very nice. I like the 'scrollspy' sidebar which highlights all visible headings.

Claude tells me this is https://www.fumadocs.dev/

sroussey•56m ago

Interesting, thanks. I need make some good docs soon.

dmix•47m ago

Good documentation is always worth the effort. Markdown explaining your products is gold these days with LLMs.

nine_k•1h ago

"We rewrote this code from language L to language M, and the result is better!" No wonder: it was a chance to rectify everything that was tangled or crooked, avoid every known bad decision, and apply newly-invented better approaches.

So this holds even for L = M. The speedup is not in the language, but in the rewriting and rethinking.

MiddleEndian•1h ago

Now they just need a third party who's never seen the original to rewrite their TypeScript solution in Rust for even more gains.

nine_k•57m ago

Indeed! But only after a year or so of using it in production, so that the drawbacks would be discovered.

baranul•40m ago

Truth. You can see improvement, even rewriting code in the same language.

spankalee•1h ago

I was wondering why I hadn't heard of Open UI doing anything with WASM.

This new company chose a very confusing name that has been used by the Open UI W3C Community Group for over 5 years.

https://open-ui.org/

Open UI is the standards group responsible for HTML having popovers, customizable select, invoker commands, and accordions. They're doing great work.

caderosche•1h ago

What is the purpose of the Rust WASM parser? Didn't understand that easily from the article. Would love a better explanation.

joshuanapoli•24m ago

They use a bespoke language to define LLM-generated UI components. I think that this is supposed to prevent exfiltration if the LLM is prompt-injected. In any case, the parser compiles chunks streaming from the LLM to build a live UI. The WASM parser restarted from the beginning upon each chunk received. Fixing this algorithm to work more incrementally (while porting from Rust to TypeScript) improved performance a lot.

evmar•41m ago

By the way, I did a deeper dive on the problem of serializing objects across the Rust/JS boundary, noticed the approach used by serde wasn’t great for performance, and explored improving it here: https://neugierig.org/software/blog/2024/04/rust-wasm-to-js....

SCLeo•31m ago

They should rewrite it in rust again to get another 3x performance increase /s

slowhadoken•26m ago

Am I mistaken or isn’t TypeScript just Golang under the hood these days?

iainmerrick•8m ago

Hmm, there's an in-progress rewrite of the TypeScript compiler in Go; is that what you mean?

I don't think that's actually out yet, and more importantly, it doesn't change anything at runtime -- your code still runs in a JS engine (V8, JSC etc).

szmarczak•12m ago

> Attempted Fix: Skip the JSON Round-Trip > We integrated serde-wasm-bindgen

So you're reinventing JSON but binary? V8 JSON nowadays is highly optimized [1] and can process gigabytes per second [2], I doubt it is a bottleneck here.

[1] https://v8.dev/blog/json-stringify [2] https://github.com/simdjson/simdjson

neuropacabra•1m ago

This is very unusual statement :-D

My heuristics are wrong. What now?

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