vendor/ryu/README.md

   1 # Ryū
   2
   3 [<img alt="github" src="https://img.shields.io/badge/github-dtolnay/ryu-8da0cb?style=for-the-badge&labelColor=555555&logo=github" height="20">](https://github.com/dtolnay/ryu)
   4 [<img alt="crates.io" src="https://img.shields.io/crates/v/ryu.svg?style=for-the-badge&color=fc8d62&logo=rust" height="20">](https://crates.io/crates/ryu)
   5 [<img alt="docs.rs" src="https://img.shields.io/badge/docs.rs-ryu-66c2a5?style=for-the-badge&labelColor=555555&logoColor=white&logo=data:image/svg+xml;base64,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" height="20">](https://docs.rs/ryu)
   6 [<img alt="build status" src="https://img.shields.io/github/workflow/status/dtolnay/ryu/CI/master?style=for-the-badge" height="20">](https://github.com/dtolnay/ryu/actions?query=branch%3Amaster)
   7
   8 Pure Rust implementation of Ryū, an algorithm to quickly convert floating point
   9 numbers to decimal strings.
  10
  11 The PLDI'18 paper [*Ryū: fast float-to-string conversion*][paper] by Ulf Adams
  12 includes a complete correctness proof of the algorithm. The paper is available
  13 under the creative commons CC-BY-SA license.
  14
  15 This Rust implementation is a line-by-line port of Ulf Adams' implementation in
  16 C, [https://github.com/ulfjack/ryu][upstream].
  17
  18 *Requirements: this crate supports any compiler version back to rustc 1.31; it
  19 uses nothing from the Rust standard library so is usable from no_std crates.*
  20
  21 [paper]: https://dl.acm.org/citation.cfm?id=3192369
  22 [upstream]: https://github.com/ulfjack/ryu/tree/1c413e127f8d02afd12eb6259bc80163722f1385
  23
  24 ```toml
  25 [dependencies]
  26 ryu = "1.0"
  27 ```
  28
  29 ## Example
  30
  31 ```rust
  32 fn main() {
  33     let mut buffer = ryu::Buffer::new();
  34     let printed = buffer.format(1.234);
  35     assert_eq!(printed, "1.234");
  36 }
  37 ```
  38
  39 ## Performance
  40
  41 You can run upstream's benchmarks with:
  42
  43 ```console
  44 $ git clone https://github.com/ulfjack/ryu c-ryu
  45 $ cd c-ryu
  46 $ bazel run -c opt //ryu/benchmark
  47 ```
  48
  49 And the same benchmark against our implementation with:
  50
  51 ```console
  52 $ git clone https://github.com/dtolnay/ryu rust-ryu
  53 $ cd rust-ryu
  54 $ cargo run --example upstream_benchmark --release
  55 ```
  56
  57 These benchmarks measure the average time to print a 32-bit float and average
  58 time to print a 64-bit float, where the inputs are distributed as uniform random
  59 bit patterns 32 and 64 bits wide.
  60
  61 The upstream C code, the unsafe direct Rust port, and the safe pretty Rust API
  62 all perform the same, taking around 21 nanoseconds to format a 32-bit float and
  63 31 nanoseconds to format a 64-bit float.
  64
  65 There is also a Rust-specific benchmark comparing this implementation to the
  66 standard library which you can run with:
  67
  68 ```console
  69 $ cargo bench
  70 ```
  71
  72 The benchmark shows Ryū approximately 4-10x faster than the standard library
  73 across a range of f32 and f64 inputs. Measurements are in nanoseconds per
  74 iteration; smaller is better.
  75
  76 | type=f32 | 0.0  | 0.1234 | 2.718281828459045 | f32::MAX |
  77 |:--------:|:----:|:------:|:-----------------:|:--------:|
  78 | RYU      | 3ns  | 28ns   | 23ns              | 22ns     |
  79 | STD      | 40ns | 106ns  | 128ns             | 110ns    |
  80
  81 | type=f64 | 0.0  | 0.1234 | 2.718281828459045 | f64::MAX |
  82 |:--------:|:----:|:------:|:-----------------:|:--------:|
  83 | RYU      | 3ns  | 50ns   | 35ns              | 32ns     |
  84 | STD      | 39ns | 105ns  | 128ns             | 202ns    |
  85
  86 ## Formatting
  87
  88 This library tends to produce more human-readable output than the standard
  89 library's to\_string, which never uses scientific notation. Here are two
  90 examples:
  91
  92 - *ryu:* 1.23e40, *std:* 12300000000000000000000000000000000000000
  93 - *ryu:* 1.23e-40, *std:* 0.000000000000000000000000000000000000000123
  94
  95 Both libraries print short decimals such as 0.0000123 without scientific
  96 notation.
  97
  98 <br>
  99
 100 #### License
 101
 102 <sup>
 103 Licensed under either of <a href="LICENSE-APACHE">Apache License, Version
 104 2.0</a> or <a href="LICENSE-BOOST">Boost Software License 1.0</a> at your
 105 option.
 106 </sup>
 107
 108 <br>
 109
 110 <sub>
 111 Unless you explicitly state otherwise, any contribution intentionally submitted
 112 for inclusion in this crate by you, as defined in the Apache-2.0 license, shall
 113 be dual licensed as above, without any additional terms or conditions.
 114 </sub>