Show HN: Zroar – Serialized Roaring Bitmaps in Zig

zroar is a ground-up implementation of Roaring Bitmaps data structure in Zig. zroar stores both the keys and (array, bitmap) containers in a single flat byte buffer, making the in-memory representation equal to the on-disk or over-the-network representation, eliminating the serialization/deserialization step entirely.

The design was originally aimed at systems which keep their posting lists on disk, but zroar performs faster than CRoaring even for purely in-memory ops, due to CPU cache locality.

Against CRoaring 5.0's benchmarking suite (ported to Zig), zroar is faster in 339 out of 360 tests, being 2x-9x faster (geometric mean), and up to 600x faster on serialize/deserialize.

zroar avoids complex mechanism (like adaptive radix trees), uses Zig native SIMD ops and is simpler. The main logic is written in ~2000 lines of code, while CRoaring's 64-bit bitmap codebase is over 17000 LOC.

Not yet: By choice, zroar doesn't support run containers, and is 64-bit only.

There are more details in the GitHub README. Try it out! I'd love feedback on the API and design. zroar is a Zig-based successor to my other project, sroar in Go, which showed a similar boost. So, I think this design should show performance gains in any language.