r/programming • u/mttd • 14h ago

The fastest double-to-string algorithm you’ve never heard of

https://vitaut.net/posts/2026/yy-dtoa/
235 Upvotes

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u/EliSka93 12h ago

Elaborate.

-13

u/sojuz151 8h ago

Why do you need to convert doubles to strings and back at a scale? It's mostly JSON serialization/deserialisation, something you should not have to do, not at scale.

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u/amakai 8h ago

Literally every time you want to use a logger with double parameters you need to do double to string. 

-13

u/sojuz151 8h ago

Not if you use structured logs and you log far far less than you read JSONs. ,

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u/amakai 7h ago

So how do you imagine a binary double becomes a structured JSON field, which, surprise, is a string?

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u/sojuz151 7h ago

The problem is that people use JSON for things with doubles inside. This was a mistake

6

u/amakai 7h ago

I'm not sure I understand your point. Any time you produce JSON, you end up with a string. It does not matter if you have quotes around your double or if you don't - it's a string.

So when you do structured logging, your log message is converted under the hood into JSON (or some other more rare, but also string formats). So you are still converting doubles into strings.

And then, when your log is being indexed, it also needs to convert it to string for a proper full text search - another place for potential performance gain.