Efim Beshmenev
74 lines
3.1 KiB
Markdown
74 lines
3.1 KiB
Markdown
# Intermediate checkpoint: bulk slack smoke v13
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This is an exploratory checkpoint, not the final benchmark set.
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## Scope
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- MSVC baseline profile: Release `/O2`, `/MT`, compiler default ISA (no
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`/arch:AVX*`).
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- `compare` suite, `smoke` scale, three repeats.
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- Six value categories and 58 valid workload/size cells per complete
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candidate.
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- Raw timings, per-cell medians, aggregate scores, and environment metadata
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are stored beside this file.
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`std::deque` and `std::list` are external comparison baselines only. The
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adaptive candidate switches exclusively between vector and tiered storage;
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`std::list` uses O(N) traversal to provide the benchmark's index semantics.
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## Change under test
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Bulk construction of tiered storage now fills each leaf to 7/8 capacity rather
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than 100%. The remaining 1/8 is deliberate insertion slack. Previously the
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first random insertion into almost every freshly built leaf forced a split and
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a directory rebuild, so the benchmark measured an avoidable bulk-layout
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pathology and the policy learned an artificially large leaf size.
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## Current result
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The hierarchical aggregate score is normalized to the best fixed baseline in
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each cell; higher is better.
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| Candidate | Score |
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|---|---:|
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| forced tiered, leaf 64 | 0.39608 |
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| forced tiered, leaf 128 | 0.36662 |
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| adaptive, deferred reads | 0.34673 |
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| adaptive, eager non-const reads | 0.32499 |
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| forced tiered, leaf 256 | 0.31051 |
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| reserved `std::vector` | 0.29797 |
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The new layout makes 64--128-element leaves the strongest fixed candidates in
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this smoke matrix. The deferred adaptive candidate is already ahead of the
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vector baseline, but it is not final: stationary edit traces still show
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unnecessary vector/tiered reversals and occasional repeated shape rebuilds.
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## Safe continuation point
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1. Add explicit read/edit phase hysteresis.
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2. Preserve the long-term EWMA across a transition while resetting only new
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residency evidence; do not relearn from a noisy empty history.
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3. Give full leaf rebuilds a separate, longer residency and a larger minimum
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improvement than directory-only changes.
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4. Add regression tests requiring at most one storage switch and at most one
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leaf rebuild on a stationary 30k-edit trace.
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5. Re-run paired `adapt`, then the three-profile quick holdout (scalar,
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baseline, AVX2).
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## Source snapshot hashes
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The repository had no initial commit at this checkpoint, so `git_head` is
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empty. These hashes identify the relevant source state:
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```text
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tiered_storage.hpp EF6086BC3C5A348793BF70008092ABD680611478D577ED05187BE2D3391D2390
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adaptive_sequence.hpp 060E7BCFC09B15EB2C20E076CE423EA3360B91915FBDB92A8D21303B1067B42F
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adaptation_policy.hpp 9D0A08AE34121C2AB76B62495E479B6C79C0A1C331DDE3269493DAB13E3E6FE9
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benchmark.cpp AA7CA2D0EF5FEAA14BDCD8EAA44449462A8C981535A62F47588798B6D456B893
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analyze_results.ps1 3BC214F7C869A99824E94F813FF380B00937DC4BE752FFB20D825F6A51B7866E
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```
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`adaptive_sequence.hpp` received a configuration-rollback safety fix after the
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timing run. It does not alter the measured fast path, but the benchmark should
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be repeated after the pending policy work.
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