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rurban/smhasher

A test suite that measures the speed and statistical quality of hash functions, with a large table of tested implementations.

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What is it?

SMHasher is a test suite for hash functions. It runs a set of speed benchmarks on bulk and small keys, measures hash-map lookup cost, and applies statistical quality tests such as collision counting, bias, avalanche and sanity checks to reveal weaknesses in a function's output.

The repository also publishes a large comparison table covering hundreds of non-cryptographic and cryptographic hash functions, including MurmurHash, xxHash, wyhash, CityHash, FarmHash, SipHash and many others. Each entry lists throughput, cycles per small hash, hash-map performance, object size, and the quality tests a function fails. Results are provided for several CPUs, from desktop x86 to a 32-bit ARM phone.

The author's conclusions are included alongside the data. They note that fast hashes with minor quality flaws often perform well in real hash tables, while security-sensitive uses need cryptographic or keyed designs.

Key features

  • 01Benchmarks bulk-key throughput and small-key hashing cost in cycles.
  • 02Measures hash-map lookup performance and object size for inlining analysis.
  • 03Runs statistical quality tests for collisions, bias, avalanche and sanity.
  • 04Publishes sortable comparison tables across several CPU platforms.

Use cases

  • Choosing a hash function for a hash table or symbol table implementation.
  • Comparing the speed and quality of candidate hashes before adopting one.
  • Validating a new hash function implementation against known test suites.
  • Studying trade-offs between hash speed, collision behavior and hash-table performance.

Things to know

  • The license is not clearly stated (metadata reports NOASSERTION), so reuse terms are unclear.

In collections

Testing frameworks & test automation tools

Topics

#hash-functions#benchmark#testing#performance#algorithms#c-plus-plus#test

FAQ

What is smhasher?
A test suite that measures the speed and statistical quality of hash functions, with a large table of tested implementations. SMHasher is a test suite for hash functions. It runs a set of speed benchmarks on bulk and small keys, measures hash-map lookup cost, and applies statistical quality tests such as collision counting, bias, avalanche and sanity checks to reveal weaknesses in a function's output.
Is smhasher free to use? What license does it have?
smhasher is open source under the Other license. Check the license terms before using it in commercial products.
Is smhasher still maintained?
Actively maintained. The last commit to smhasher was on Oct 22, 2026.
What can I use smhasher for?
Choosing a hash function for a hash table or symbol table implementation. Comparing the speed and quality of candidate hashes before adopting one. Validating a new hash function implementation against known test suites. Studying trade-offs between hash speed, collision behavior and hash-table performance.
Where can I get smhasher?
The source code and installation instructions are on GitHub: https://github.com/rurban/smhasher

Summary generated by AI from the project's README. GitHub stats refresh daily.

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