sparsehash/sparsehash

Health v2 · maintenance only

Adoption not part of the score

1599 stars · 260 forks observed · 2026-08-28

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

A C++ library providing sparse_hash_map, dense_hash_map, and their set counterparts — hash-based associative containers with SGI hash_map-compatible APIs but different space/speed tradeoffs. sparse variants use only 1-2 bits of overhead per entry, while dense variants optimize lookup speed.

Use cases

• store huge hash maps with minimal memory overhead
• fast hash map lookups in C++
• replace std::unordered_map with a space-efficient alternative
• serialize hash maps to disk
• use hash sets with low per-entry overhead

When to choose

• memory footprint is critical for very large hash tables
• you need faster lookups than std::unordered_map and can tolerate API quirks like empty/deleted key reservation
• you want a mature, header-based C++ hashtable with I/O support

When to avoid

• you need a modern, actively maintained container — prefer absl::flat_hash_map or std::unordered_map
• your keys cannot reserve sentinel empty/deleted values
• you need rich iterator semantics or C++ standard compliance

Facets

library · maturity maintenance

caching serialization developer-tools performance developer-tools cpp windows cross-platform hash-map hash-set associative-containers hashtable memory-efficient header-only algorithms linux macos

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