#checksum #simd #fletchers

nightly fletcher-simd

A SIMD implementation of the Fletcher's checksum algorithm

5 releases (3 breaking)

0.4.0 Nov 8, 2022
0.3.0 Mar 2, 2022
0.2.0 Mar 1, 2022
0.1.1 Feb 19, 2022
0.1.0 Feb 15, 2022

#1778 in Algorithms


217 lines


crates.io crates.io docs.rs

A SIMD implementation of the Fletcher's checksum algorithm.

Note: This implementation uses a modulus of 2^k where k is the checksum block size in bits, as this is fast with wrapping math. Other implementations may use 2^k - 1.


  • Uses std::simd, which currently requires nightly.
  • Supports all architectures supported by std::simd.
  • Both run-time and compile-time detection available via the multiversion crate.
  • Scalar fallback.

Cargo features

There is one cargo feature, runtime_dispatch, enabled by default. When enabled, the crate will use CPU feature detection at runtime to dispatch to the appropriate SIMD implementation. Disabling this feature will result in static dispatch only.


use byteorder::{ByteOrder, LittleEndian};
use fletcher_simd::Fletcher128;

fn main() {
    const DATA: &str = "abcdefgh";
    let mut fletcher = Fletcher128::new();

    // Read bytes in little endian. Endianness matters!
            .map(|chunk| LittleEndian::read_u64(chunk)),

    assert_eq!(fletcher.value(), 0x68676665646362616867666564636261);


~41K SLoC