Converting an Integer to a Decimal String in Under Two Nanoseconds
This work provides a faster integer-to-string conversion for software developers, offering significant performance gains over existing methods.
The paper presents a SIMD-based algorithm for converting binary integers to decimal strings that eliminates lookup tables and uses integer multiply-add instructions. The method achieves 1.4-2x speedup over the closest competitor and 2-4x over std::to_chars across all integer sizes.
Converting binary integers to variable-length decimal strings is a fundamental operation in computing. Conventional fast approaches rely on recursive division and small lookup tables. We propose a SIMD-based algorithm that leverages integer multiply-add instructions available on recent AMD and Intel processors. Our method eliminates lookup tables entirely and computes multiple quotients and remainders in parallel. Additionally, we introduce a dual-variant design with dynamic selection that adapts to input characteristics: a branch-heavy variant optimized for homogeneous digit-length distributions and a branch-light variant for heterogeneous datasets. Our single-core algorithm consistently outperforms all competing methods across the full range of integer sizes, running 1.4-2x faster than the closest competitor and 2-4x faster than the C++ standard library function std::to_chars across tested workloads.