- Cosine distance was 1 - dot/(|a||b|), re-deriving both norms on every
evaluation in the innermost loop of build and search. The index now stores
unit vectors (prepared at build, insert, graph load and HDF5 load; the query
once per search) and uses 1 - dot. Zero vectors stay zero, giving distance 1
as before. Returned distances are unchanged.
- search_layer allocated a HashSet of visited nodes per call. It is now an
epoch-stamped u32 array in thread-local scratch, reused across calls, so
search(&self) stays shareable between threads.
- clawhdf5-accel caches the detected SIMD backend in a OnceLock.
Recall is identical. Build 2.75 -> 1.89 s (10K), ~38 -> 21 s (100K); QPS at
ef=64 22.7K -> 39K (10K), 10.4K -> 14K (100K).
Co-Authored-By: Claude Fable 5.1 <[email protected]>
