dragonbox

The part that was most surprising to me was how much the performance of serializing floating-point numbers has improved, even just in the past decade [1]. [1] https://github.com/jk-jeon/dragonbox?tab=readme-ov-file#perf...

AFAIK the state of the art now is "dragonbox": https://github.com/jk-jeon/dragonbox

Something like that. The Dragonbox author reports[1] about 25 ns/conversion, Cox reports 1e5 conversions/s, so that’s a factor of 400. We can probably knock off half an order of magnitude for CPU differences if we’re generous (midrange performance-oriented Kaby Lake laptop CPU from 2017 vs Cox’s unspecified laptop CPU ca. 2010), but that’s still a factor of 100. Still a performance chasm. You can likely get some of the performance back by picking the low-hanging fruit, e.g. switching from dumb one-byte bigint limbs in [0,10) to somewhat less dumb 32-bit limbs in [0,1e9). But generally, yes, this looks like a teaching- and microcontroller-class algorithm more than anything I’d want to use on a modern machine. [1] https://github.com/jk-jeon/dragonbox/blob/master/README.md#p...

https://github.com/jk-jeon/dragonbox/discussions/57#discussi... We have been doing some experiment on optimizing for size, and currently it can be reduced to ~3k on 8-bit AVR. It only contains impl/table for single-precision binary32, and double-precision requires quite more, but at the same time much of the bloat is due to how limited AVR is. On platforms like x64 it should be much smaller. You can certainly say 3k is still huge though.

It's kind of mindblowing to see how much code floating point formatting needs. The linked dragonbox [1] project is also worth a read. Pretty optimized for the least used branches. [1] https://github.com/jk-jeon/dragonbox

Apparently exact minimal float-to-string conversion is more recent than I thought, and many languages used to print more (Python?) or less (PHP) decimal digits than necessary to uniquely identify the bit pattern. Python correctly prints 46000.80 + 553.04 as 46553.840000000004, but I don't know if it ever prints more digits than needed. One recent algorithm for printing floats exactly is https://github.com/ulfjack/ryu, though I'm unaware what's the state-of-the-art (https://github.com/jk-jeon/dragonbox claims to be a benchmark and the best algorithm).