folly::external::rapidhashMicro_with_seed

Synopsis

Declared in <folly/external/rapidhash/rapidhash.h>

constexpr
uint64_t
rapidhashMicro_with_seed(
    char const* key,
    size_t len,
    uint64_t seed) noexcept;

Description

Designed for HPC and server applications, where cache misses make a noticeable performance detriment. Clang-18+ compiles it to ~140 instructions without stack usage, both on x86-64 and aarch64. Faster for sizes up to 512 bytes, just 15%-20% slower for inputs above 1kb.

Calls rapidhashMicro_internal using the provided parameters and default secrets.

Return Value

A 64-bit hash.

Parameters

Name	Description
key	Buffer to be hashed.
len	Length of key, in bytes.
seed	64-bit seed used to alter the hash result predictably.