| commit | 696554c816dd373f5ece47d994419e17c553f7c8 | [log] [tgz] |
|---|---|---|
| author | Chris Wailes <[email protected]> | Fri May 10 00:00:00 2024 +0000 |
| committer | Automerger Merge Worker <[email protected]> | Fri May 10 00:00:00 2024 +0000 |
| tree | d4de3b36b81e52573ce13f7fa8292560cd7b6686 | |
| parent | c30a2e9cd205738d3bd818b102f2a61b7ed5104c [diff] | |
| parent | 7fbea3ee64f3b3c18789c4f55569e8f3e517b85b [diff] |
Ensure crate is compiled with std for panic handler am: 62957d8e33 am: 7fbea3ee64 Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/ryu/+/3080641 Change-Id: I156da24b8df41facc69e35b3f988a7999b004265 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.