Th64: Tiny Hash Function in C
A compact hash function "th64" on GitHub excels in performance, passing SMhasher3 tests. It achieves 43 cycles per hash for small keys and 2.61 bytes per cycle for larger keys, operating at 8.52 GiB per second. The function's C code demonstrates efficient data processing with a versatile design for different key sizes. It is available under public domain or MIT-0 license for flexible usage.
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The "th64" project on GitHub presents a compact hash function in C language that successfully passes all tests in SMhasher3. This function demonstrates high performance, achieving 43 cycles per hash for small keys (1-32 bytes) and 2.61 bytes per cycle for larger keys, equivalent to 8.52 GiB per second. The provided C code for the "th64" hash function showcases its implementation, utilizing a specific algorithm to process data efficiently. The function is designed to operate swiftly for various key sizes, enhancing its versatility. Additionally, the project offers the hash function under either the public domain or MIT-0 license, allowing for flexible usage and modification within the specified licensing terms.
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10 commentsWith the code-golfing obfuscation unwound, Th64 is structured very similarly to MurmurHash. The source data is pre-mixed via "rol(x * r + i, 31)", the hash is mixed via "hash = rol(hash * r ^ x, 31)", the tail bytes are mixed via "hash = hash * r ^ x", and the finalization mix is three "hash = (hash ^ (hash >> 31)) * r" rounds.
I see nothing wrong with it if it passes SMHasher3, but it's also not radically different than other hashes - it's just smooshed down into four lines.
Otherwise just an experiment.
* ~~It requires two passes over the data to hash (notice the two while loops).~~ Actually it doesn't.
* The first loop casts the data pointer to a 64-bit int, so you will get different results depending on endianness. I don't remember if this is undefined behavior or not.
And I have to admin that this kind of obfuscation/minification is especially dangerous in languages such as C as there are quite a lot of footguns already as it is. I don't think that minifying C produces faster programs :)
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