Non-cryptographic

CityHash & FarmHash

Two generations of Google’s fast string-hash families. CityHash(Geoff Pike & Jyrki Alakuijala, 2011) was designed as a faster, better-distributed Murmur with platform-specific paths. FarmHash (2014) refined the architecture, exposed cleaner APIs (Hash64, Hash128), and added CPU-feature-dispatch wrappers.

At a glance

Where they are used

• Google products internally , the original brief was that internal use required Murmur-class speed with measurably better distribution under SMHasher.
• Bazel , content addressing for build outputs (Bazel uses BLAKE3 today but FarmHash was a step on the way).
• Apache Beam / Dataflow , keys for grouping operations.
• ClickHouse , cityHash64 and farmHash64 are standard SQL functions.
• HyperLogLog implementations in C++ , popular short-input hashes.

Differences vs MurmurHash

• Better distribution under SMHasher , Google fixed several mid-range Murmur failures.
• CPU-dispatching , CityHash had SSE4.2 / CRC32 instructions paths; FarmHash generalized this.
• Larger outputs , CityHash128 and FarmHash128 are first-class, not bolt-ons.

And vs xxHash3?

xxHash3 (2019) is faster on most modern CPUs and has cleaner SIMD scalability. CityHash / FarmHash remain in production for legacy reasons and for inter-product reproducibility with Google’s ecosystem.

References

• google/cityhash , reference implementation
• google/farmhash , reference implementation
• SMHasher , the comparison bench every non-crypto hash gets measured against
• xxHash3 · MurmurHash3