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Algorithm Profiles

Chronicle Software

CityHash 1.1

Factories

LongHashFunction.city_1_1(), .city_1_1(long), .city_1_1(long, long) (LongHashFunction.java:53-115).

Implementation

net.openhft.hashing.CityAndFarmHash_1_1 ports Google’s CityHash64 v1.1 (CityAndFarmHash_1_1.java).

Key traits

  • Normalises inputs to little-endian and forwards short-length cases to specialised mix routines (1–3, 4–7, 8–16 byte fast paths).

  • Produces identical output across host endianness; big-endian incurs the expected byte swapping cost.

  • Provides seedless, single-seed, and dual-seed variants mirroring the upstream API.

FarmHash NA (1.0)

Factories

LongHashFunction.farmNa(), .farmNa(long), .farmNa(long, long) (LongHashFunction.java:117-179).

Implementation

Shares CityAndFarmHash_1_1 with CityHash; the class carries the farmhashna logic, including the <32 byte shortcut to CityHash output.

Key traits

  • Deterministic across endianness; the mixing rounds assume little-endian inputs and convert when necessary.

  • Seeds map directly onto the upstream farmhashna parameters.

FarmHash UO (1.1)

Factories

LongHashFunction.farmUo(), .farmUo(long), .farmUo(long, long) (LongHashFunction.java:181-243).

Implementation

Also hosted in CityAndFarmHash_1_1, which covers the 1.1 update’s longer pipelines.

Key traits

  • Maintains parity with Google’s C++ release for test vectors.

  • Endianness neutral: always routes through an Access view that matches the algorithm’s little-endian assumptions.

MurmurHash3

Factories

LongHashFunction.murmur_3(), .murmur_3(long) for 64-bit (LongHashFunction.java:245-268); LongTupleHashFunction.murmur_3(), .murmur_3(long) for 128-bit (LongTupleHashFunction.java:35-69).

Implementation

net.openhft.hashing.MurmurHash_3 adapts Austin Appleby’s x64 variants. It extends DualHashFunction so the 128-bit engine also exposes the low 64 bits through LongHashFunction.

Key traits

  • Little-endian canonicalisation via Access.byteOrder.

  • Supports zero-length hashing through pre-computed constants to keep hashVoid() stable.

xxHash (XXH64)

Factories

LongHashFunction.xx(), .xx(long) (LongHashFunction.java:270-298).

Implementation

net.openhft.hashing.XxHash ports the official XXH64 reference and keeps the unsigned prime constants as signed Java longs.

Key traits

  • Uses four-lane accumulation for ≥32 byte inputs, matching upstream behaviour bit-for-bit.

  • Applies the canonical avalanche round in XxHash.finalize for all lengths.

  • Seeded and seedless instances differ only by the stored seed() override; serialisation preserves both forms.

XXH3 / XXH128

Factories

LongHashFunction.xx3(), .xx3(long) for 64-bit, plus .xx128low() / .xx128low(long) for the low 64 bits of XXH128 (LongHashFunction.java:300-341). Full 128-bit results live behind LongTupleHashFunction.xx128() and .xx128(long) (LongTupleHashFunction.java:71-104).

Implementation

net.openhft.hashing.XXH3 keeps the FARSH-derived 192 byte secret and streaming logic. It defines distinct entry points for 64-bit, 128-bit, and low-64-bit projections.

Key traits

  • Optimises for short messages with dedicated 1–3, 4–8, 9–16, 17–128, and 129–240 byte paths.

  • Uses UnsafeAccess.INSTANCE.byteOrder(null, LITTLE_ENDIAN) once to avoid per-call adapter allocation.

  • The 128-bit variant reuses the same mixing core; exposing the low 64 bits avoids extra copies for callers that only need a single long.

wyHash v3

Factories

LongHashFunction.wy_3(), .wy_3(long) (LongHashFunction.java:343-369).

Implementation

net.openhft.hashing.WyHash mirrors Wang Yi’s version 3 reference, including the _wymum 128-bit multiply-fold helper built on Maths.unsignedLongMulXorFold.

Key traits

  • Supports streaming chunks up to 256 bytes per loop iteration; beyond that it accumulates in 32 byte strides.

  • Handles ≤3, ≤8, ≤16, ≤24, ≤32 byte inputs with the same branching as the C code.

  • Maintains deterministic output across architectures while acknowledging the performance hit on big-endian systems.

MetroHash (metrohash64_2)

Factories

LongHashFunction.metro(), .metro(long) (LongHashFunction.java:371-389).

Implementation

net.openhft.hashing.MetroHash implements the 64-bit metrohash variant with the _2 initialisation vector, matching the original author’s reference.

Key traits

  • Performs four-lane unrolled mixing for ≥32 byte inputs and cascades down to 16, 8, 4, 2, and 1 byte tails.

  • Uses deterministic finalisation (MetroHash.finalize) shared by scalar and streaming paths.

  • Seeded instances override seed() and cache the pre-hashed hashVoid() constant to avoid re-computation.