opthash

Rust implementations of Elastic Hashing and Funnel Hashing from Optimal Bounds for Open Addressing Without Reordering (Farach-Colton, Krapivin, Kuszmaul, 2025) — open-addressing hash maps that achieve optimal expected probe complexity without reordering elements after insertion.

Both maps share a single-arena allocation indexed by per-level descriptors, 7-bit fingerprint control bytes, SIMD control-byte scans for occupancy and lookup, and per-level salt re-randomization to decorrelate probe paths across levels. They differ in how they probe within a level. Published to crates.io and PyPI (via PyO3 bindings), with CI and continuous benchmarking.

Tech stack: Rust, PyO3, SIMD.