Implements a compact, row-major sparse bit matrix backed by memory-mapped components, introducing EliasFano, PersistentFixedIntVec, and PersistentRankSelectBitVec primitives for efficient storage and decoding. Adds a BinaryMatrix trait to unify row-level operations across dense and sparse implementations. Corrects edge-case behaviors for zero-width bit storage and cardinality-0 rows. Delivers reduced on-disk size and faster random row access, with column reads remaining dense-only. Test suites and benchmarks are included but currently marked as ignored.
Eric Coissac
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