| commit | ce2049f2def63421fb5873bfd8b5d97e65813bac | [log] [tgz] |
|---|---|---|
| author | Matthew Maurer <[email protected]> | Thu Mar 09 16:09:18 2023 +0000 |
| committer | Automerger Merge Worker <[email protected]> | Thu Mar 09 16:09:18 2023 +0000 |
| tree | 0c9ba898dd9570a05e788ae4d31c7babd3d98b5b | |
| parent | 29aed2e892bee3a6381d176e1ac2f553925ec52d [diff] | |
| parent | d6ef26242c0ad12a1cdb0e6467bc2aa6b9f0520e [diff] |
Make ryu available to product and vendor am: 689fcd293b am: d6ef26242c Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/ryu/+/2476345 Change-Id: I1846dd4cc84d6c5ed1001f3877a52458021afd6a Signed-off-by: Automerger Merge Worker <[email protected]>
Pure Rust implementation of Ryū, an algorithm to quickly convert floating point numbers to decimal strings.
The PLDI'18 paper Ryū: fast float-to-string conversion by Ulf Adams includes a complete correctness proof of the algorithm. The paper is available under the creative commons CC-BY-SA license.
This Rust implementation is a line-by-line port of Ulf Adams' implementation in C, https://github.com/ulfjack/ryu.
Requirements: this crate supports any compiler version back to rustc 1.36; it uses nothing from the Rust standard library so is usable from no_std crates.
[dependencies] ryu = "1.0"
fn main() { let mut buffer = ryu::Buffer::new(); let printed = buffer.format(1.234); assert_eq!(printed, "1.234"); }
You can run upstream's benchmarks with:
$ git clone https://github.com/ulfjack/ryu c-ryu $ cd c-ryu $ bazel run -c opt //ryu/benchmark:ryu_benchmark
And the same benchmark against our implementation with:
$ git clone https://github.com/dtolnay/ryu rust-ryu $ cd rust-ryu $ cargo run --example upstream_benchmark --release
These benchmarks measure the average time to print a 32-bit float and average time to print a 64-bit float, where the inputs are distributed as uniform random bit patterns 32 and 64 bits wide.
The upstream C code, the unsafe direct Rust port, and the safe pretty Rust API all perform the same, taking around 21 nanoseconds to format a 32-bit float and 31 nanoseconds to format a 64-bit float.
There is also a Rust-specific benchmark comparing this implementation to the standard library which you can run with:
$ cargo bench
The benchmark shows Ryū approximately 2-5x faster than the standard library across a range of f32 and f64 inputs. Measurements are in nanoseconds per iteration; smaller is better.
This library tends to produce more human-readable output than the standard library's to_string, which never uses scientific notation. Here are two examples:
Both libraries print short decimals such as 0.0000123 without scientific notation.