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…
What it does
Serialized Roaring Bitmaps in Zig. Contribute to manishrjain/zroar development by creating an account on GitHub.
zroar is a ground-up implementation of the popular roaring bitmaps data structure in a serialized form. zroar keeps all the MSB 48-bit keys (high48) and containers in a single flat byte buffer, so the in-memory form of zroar is the serialized form, which can then be stored to disk or sent over the network as is. When opening a zroar buffer, there's no parsing or per-container allocation. All read/write operations can be done on the buffer immediately. The hot paths are explicitly vectorized with SIMD using Zig's native support: container searches, set operations on both container types, and extracting values out into arrays. zroar — one single buffer ┌───────────────────────────┐…from github.com
In the maker’s words, at launch
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.
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