LLM-written Rust ordered map bbtree claims 5x single-thread, 12x multi-thread speedups
lmoroney · x · 2026-10-27
Laurence Moroney highlights bbtree, a Rust ordered map by Xiangpeng Hao (who built Bf-Tree running in production at Microsoft), where LLMs wrote all implementation and models from different providers cross-checked it, while Hao made every design decision.
- Performance: benchmarks show 5x faster than std's BTreeMap on one thread and 12x faster than crossbeam-skiplist at 96 threads; an independent tester mostly reproduced the speedups, though the 30% memory saving reversed on stock glibc malloc.
- Correctness machinery: differential fuzzing against std's BTreeMap with invariant checks, Verus proofs for key properties, and deterministic simulation with Shuttle — yet a second tool (ffs) still caught a race Shuttle missed, now fixed.
- His advice: if AI writes most of your code, add a fuzz test comparing one module against a trusted reference this week.
Related event: Developer Releases bbtree, Claimed Fastest Concurrent B-tree(2 posts)→
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