Converting an integer to a decimal string in under two nanoseconds [r-libre/4056]

Champagne Gareau, Jaël et Lemire, Daniel ORCID: https://orcid.org/0000-0003-3306-6922 (In Press). Converting an integer to a decimal string in under two nanoseconds. Software: Practice and Experience.

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Item Type:	Journal Articles
Refereed:	Yes
Status:	In Press
Abstract:	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.
Depositor:	Lemire, Daniel
Owner / Manager:	Daniel Lemire
Deposited:	29 Apr 2026 15:57
Last Modified:	05 May 2026 18:51

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