static_maps: consteval std::map and std::unordered_map Implementations in C++23

TL;DR

This paper introduces static_maps, a C++23 library that uses consteval to create highly efficient compile-time maps, outperforming existing solutions in speed for various lookup tasks.

Contribution

The paper presents the first implementation of compile-time std::map and std::unordered_map in C++23 using consteval, achieving superior performance over existing methods.

Findings

Unordered_map runtimes are less than 40% of std::unordered_map in tests.

Library runtimes are significantly faster than Frozen, PTHash, and gperf.

Achieves the fastest drop-in alternative to std::unordered_map.

Abstract

Using consteval from C++23, we implement efficient, new versions of std::map and std::unordered_map for use when the keys are known at compile time. We demonstrate superior performance of our unordered_map on three demonstration use-cases: Lookup of elemental mass from atomic symbol, lookup of amino acid from codon, and modification of stock prices from S&P 500 ticker symbols all produced runtimes <40%, <35%, <73% of the respective runtimes of the std implementations. Our library runimes were <80%, <45%, <97% of the lookup time of Frozen, an alternative perfect hashing implementation in C++ for problems also using constexpr keys. To our knowledge, this makes our library the overall fastest drop-in (i.e., with a similar API) alternative to std::unordered_map. On one arbitrarily chosen demo, we demonstrate runtimes <35% of PTHash and <89% gperf, state-of-the-art but not drop-in hashing libraries via external tools.