fast_float
dragonbox
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fast_float | dragonbox | |
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15 | 9 | |
1,269 | 494 | |
2.0% | - | |
8.7 | 8.2 | |
about 1 month ago | 5 days ago | |
C++ | C++ | |
Apache License 2.0 | Apache License 2.0 |
Stars - the number of stars that a project has on GitHub. Growth - month over month growth in stars.
Activity is a relative number indicating how actively a project is being developed. Recent commits have higher weight than older ones.
For example, an activity of 9.0 indicates that a project is amongst the top 10% of the most actively developed projects that we are tracking.
fast_float
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Parquet: More than just “Turbo CSV”
> Google put in significant engineering effort into "Ryu", a parsing library for double-precision floating point numbers: https://github.com/ulfjack/ryu
It's not a parsing library, but a printing one, i.e., double -> string. https://github.com/fastfloat/fast_float is a parsing library, i.e., string -> double, not by Google though, but was indeed motivated by parsing JSON fast https://lemire.me/blog/2020/03/10/fast-float-parsing-in-prac...
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What do number conversions (from string) cost?
For those that don't know, gcc 12.x updated its float parsing logic to something similar to fast_float and it's about 1/6 of the cost presented here (sub 100 in the graph presented here). Strongly suggest using that library or upgrading the compiler if you need the performance.
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Can sanitizers find the two bugs I wrote in C++?
This makes sense for integers but betware floating point from_chars - libc++ still doesn't implement it and libstdc++ implements it by wrapping locale-dependent libc functions which involves temporarily changing the thread locale and possibly memory allocation to make the passed string 0-terminated. IMO libstdc++'s checkbox "solution" is worse than not implementing it at all - user's are better off using Lemire's API-compatible fast_float implementation [0].
[0] https://github.com/fastfloat/fast_float
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Passing Programs To A Stack Machine
I'm a bit stuck on how to do the same thing in c++, due to containers only having a single type. The very inefficient way I'm currently doing it is by passing a program as a vector of strings, and then converting the string constants to doubles with the fast_float library.
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Parsing can become accidentally quadratic because of sscanf
Just above this comment is a merged PR, which references fast_float library: https://github.com/fastfloat/fast_float
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Making Rust Float Parsing Fast: libcore Edition
Daniel Lemire @lemire (creator of the algorithm, author of the C++ implementation, and provided constant feedback to help guide the PR).
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RapidObj v0.1 - A fast, header-only, C++17 library for parsing Wavefront .obj files.
And out of 6,000 lines in the file, at least 3000 are other people's code: earcut for polygon triangulation and fast_float because .obj files typically contain a lot of floating point numbers so it's important to parse them quickly.
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First release of dragonbox, a fast float-to-string conversion algorithm, is available
How this compares to https://github.com/fastfloat/fast_float ?
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Why is std::from_chars<float> slow?
I tried to compare it against Daniel Lemire's excellent fast_float library. Fast float took about 180ms for the same program, and all I did was change "std" namespace prefix to "fast_float". It's a factor of 12 difference, at least my machine. I tried MSVC next, and it is a lot better, but it is still ~4 times slower than fast float. AFAIK, clang currently does not implement the feature at all.
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Iterator invalidation of std::string_view
If you don't mind a 3rd party lib until your stdlib updates, https://github.com/fastfloat/fast_float is best-in-class.
dragonbox
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23 years into my career, I still love PHP and JavaScript
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).
- Dragonbox: Fast Float-to-String Conversion
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C++ I wrote a simple and fast formatting library for strings
A recent update to fmt was posted to r/cpp 3 days ago (https://www.reddit.com/r/cpp/comments/vrxkt0/fmt_90_released_with_improvements_to_floating/), and since that's still fresh on people's minds, they'll wonder how yours compares; and they'll probably wonder how it compares in terms of precision, round trip-ability, and performance of DragonBox https://github.com/jk-jeon/dragonbox. By "they", I probably mean "me" :D.
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I created something much faster than a std::string
Existing fast and correct float-to-string implementations are out there. Just use them: https://github.com/jk-jeon/dragonbox. Or maybe use your stdlib if it has good support
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How to read ascii files faster?
Parse floats faster with dragonbox
- Dragonbox 1.1.0 is released (a fast float-to-string conversion algorithm)
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C++20 std::format is already std::regex 2.0 situation.
Even if what you say is true, it makes little sense to not reuse it. There are other concerns here and one of them is code size. But to address the performance issue, fmtlib is doing under 50ns for most fp numbers via dragonbox(https://github.com/jk-jeon/dragonbox has the chart). So still cpu bound, but all FP output is CPU bound. At this point, what prices are we trading for faster?
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First release of dragonbox, a fast float-to-string conversion algorithm, is available
There are some benchmarks in https://github.com/jk-jeon/dragonbox#performance. TL;DR it's faster than other state of the art algorithms like Ryu, Schubfach and variations of Grisu. We saw a nice speed up when switching from Grisu3 to Dragonbox in {fmt}: https://github.com/fmtlib/fmt/pull/1882 and it has been improved even more since then.
What are some alternatives?
rapidobj - A fast, header-only, C++17 library for parsing Wavefront .obj files.
C++ Format - A modern formatting library
ryu - Converts floating point numbers to decimal strings
fast-float-rust - Super-fast float parser in Rust (now part of Rust core)
ryu - Ryu component-based software defined networking framework
RapidJSON - A fast JSON parser/generator for C++ with both SAX/DOM style API
dtoa-benchmark - C++ double-to-string conversion benchmark
earcut.hpp - Fast, header-only polygon triangulation
itoa - Fast integer to ascii / integer to string conversion
simdutf8 - SIMD-accelerated UTF-8 validation for Rust.
cpp-xstring - A system to handle strings easier and faster