Sparse Bitsets

A sparse bitset is a data structure that efficiently represents a large set of bits where most are zero. Instead of storing a full bit array, which would be wasteful if the set is mostly empty, a sparse bitset uses techniques like run-length encoding or a tree-based structure to store only the bits that are set to one.

This significantly reduces the memory and storage requirements for managing large, sparse datasets. In smart contracts, sparse bitsets can be used to track large numbers of flags or status indicators, such as user permissions or participation in a large-scale event, without consuming excessive storage.

They offer a balance between space efficiency and performance, making them suitable for complex protocol state management. By only recording the non-zero bits, developers can maintain large logical arrays with minimal cost.