Harder, Better, Faster, Stronger version of Uber H3 in Rust: The Hydronium Project — grim7reaper

h3o is a complete Rust rewrite of Uber's H3 geospatial indexing library, achieving significant performance improvements (up to 55x faster in some operations) through optimizations like constant-time algorithms, efficient data structures, and bit manipulation. The project includes comprehensive testing with 964 test cases, differential testing against H3, and 15 fuzz targets. It provides a C-compatible binding (h3oh3o) for easy integration with existing H3 projects, a CLI tool for geospatial operations, and THC compression achieving up to 469x size reduction for dense index sets. Benchmarks show h3o outperforms H3 in 862 of 911 test cases while maintaining API compatibility.