martinus/unordered_dense

Health v2 · maintenance only

Adoption not part of the score

1479 stars · 119 forks observed · 2026-09-21

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-30, confidence not recorded

A fast, densely stored C++17 hashmap and hashset library based on robin-hood hashing with backward shift deletion. It provides drop-in replacements for std::unordered_map and std::unordered_set that are typically much faster, plus segmented variants with lower peak memory usage.

Use cases

• replace std::unordered_map with a faster hashmap
• speed up hash set lookups in C++ code
• store hash maps densely to reduce memory usage
• get stable references on insert with segmented_map
• use a header-only hash table with no dependencies

When to choose

• you need faster unordered containers than the STL and can tolerate weaker iterator stability
• you want a header-only, dependency-free C++17 container library
• memory locality and iteration speed matter more than pointer stability

When to avoid

• you require full iterator and reference stability across rehashing and deletion
• you need exact std::unordered_map API compatibility in every detail

Facets

library · maturity stable

caching developer-tools performance developer-tools cpp cross-platform hashmap hashset robin-hood header-only stl-containers cpp17 data-structures algorithms

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