CppCon 2017: Matt Kulukundis “Designing a Fast, Efficient, Cache-friendly Hash Table, Step by Step”

CppCon · 137.3K views · 2017-10-26 · 59:34

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Overview

Matt Kulukundis explains how Google designed SwissTable, a fast, cache-friendly hash table, step by step from std::unordered_map. The talk covers open addressing, SIMD probing and the tradeoffs of changing a fundamental data structure.

On Hacker News

HN repeatedly cites it as the definitive explanation of SwissTable, the design behind Abseil, Rust's hash map and Go's maps.

Recommended by 9 HN people across 10 months · HN mentions 2018–2026

Topics

Algorithms & data structures Software performance & optimization C, C++, Rust, Go & systems languages

What people said

lalitmaganti · 2026-07 · Strong recommendation
Have to plug the original Swiss Table talk by Matt Kulukundis: [VIDEO] Excellent talk which explains the concepts really clearly and concisely.
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KerrickStaley · 2022-11 · Strong recommendation
Related: this talk [VIDEO] about the making of absl::flat_hash_map (a "competitor" to boost::unordered_flat_map) is one of my favorites.
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sujayakar · 2021-03 · Strong recommendation
Very cool! Independent of the cool use of `aesenc` and `aesdec`, the features for skipping ahead in the random stream and forking a separate stream are awesome. > My current home project is bump-allocator + semi-space garbage collection in SIMD for GPUs. As far as I can tell, both bump-allocation and semi-space garbage collection are easily SIMDified in an obvious manner. And since cudamalloc is fully synchronous, I wanted a more scalable, parallel solution to the GPU memory allocation problem. This is a great idea. I wonder if we could speed up LuaJIT even more by SIMD accelerating the GC's mark and/or sweep phases... If you're interested in more work in this area, a former coworker wrote a neat SPMD implementation of librsync [1]. And, if you haven't seen it, the talk on SwissTable [2] (Google's SIMD accelerated hash table) is excellent. [1] [LINK] [2] [VIDEO]
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Sources

Video by CppCon, played through YouTube.

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