fast_double_parser

I also did this when searching for a fast string-to-float conversion function for ClickHouse: https://github.com/ClickHouse/ClickHouse/blob/master/src/IO/... - we create a table, insert all four billion floats there, and check our functions with SQL queries. Currently, the state-of-the-art library is https://github.com/lemire/fast_double_parser, but we use a slightly worse (but more performant) routine. It is also interesting how to format floats in string in an efficient and user-friendly way. For this problem, we switched iteratively: strtod -> Google's Double Conversion -> Ryu (patched) -> Dragonbox. Currently, we use Dragonbox.

He touched on JSON parsers in a previous post about fast_double_parser: "People who write fast parsers tend to roll their own number parsers (e.g., RapidJSON, sajson), and so we did. However, we sacrifice some standard compliance." (The "we" in this context refers to simdjson.) https://lemire.me/blog/2020/03/10/fast-float-parsing-in-prac... He followed up in a comment: "RapidJSON has at least two fast-parsing mode. The fast mode, which I think is what you refer to, is indeed quite fast, but it can be off by one ULP, so it is not standard compliant." The Github README for this new project says, "The fast_float library provides a performance similar to that of the fast_double_parser library." https://github.com/fastfloat/fast_float However, the benchmarks show a significant improvement relative to those in the fast_double_parser README: h

It has about 15 KB of data: 10KB in power_of_ten_components and 5KB in mantissa_128. [1] That's ~23% of the per-core L1 data cache on (eg) the recently announced APU chip. [2, 3] So before getting too excited about the microbenchmark numbers, I'd be careful to ensure the additional cache pressure doesn't slow down my program as a whole. edit: also, ~2.5KB of that is due to padding in power_of_ten_components. I wonder if it'd be better to split the uint64_t field into two uint32_ts to avoid this. [1] https://github.com/lemire/fast_double_parser/blob/master/inc... [2] https://news.ycombinator.com/item?id=22440894 [3] https://en.wikichip.org/wiki/amd/ryzen_embedded/r1606g