Timothy Flynn 3355fb39ae AK+LibJS: Replace home-grown Ryu implementation with fmt's dragonbox ...

In the benchmark added here, fmt's dragonbox is ~3x faster than our own
Ryu implementation (1197ms for dragonbox vs. 3435ms for Ryu).

Daniel Lemire recently published an article about these algorithms:
https://lemire.me/blog/2026/02/01/converting-floats-to-strings-quickly/

In this article, fmt's dragonbox implementation is actually one of the
slower ones (with the caveat that some comments note that the article is
a bit out-of-date). I've gone with fmt here because:

1. It has a readily available recent version on vcpkg.
2. It provides the methods we need to actually convert a floating point
   to decimal exponential form.
3. There is an ongoing effort to replace dragonbox with a new algorithm,
   zmij, which promises to be faster.
4. It is one of the only users of AK/UFixedBigInt, so we can potentially
   remove that as well soon.
5. Bringing in fmt opens the door to replacing a bunch of AK::format
   facilities with fmt as well.

2026-02-23 18:30:40 +01:00

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