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fix(update): UpdatePlan must not read the destination when beta == 0; add execute_uninit - #317
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UpdatePlan::execute and ErasedUpdatePlan::execute always replayed
`alpha*f(src) + beta*dst`, so even beta == 0 read the old destination.
BLAS semantics (and the fresh-output accumulate tcontract needs) require
beta == 0 to be write-only: otherwise NaN/garbage in D propagates through
0 * NaN and a fresh output can never be represented as uninitialized.
- Branch on num_traits::{Zero, One, PartialEq}: beta.is_zero() replays
`*dst = alpha * value` (or `*dst = value` when alpha.is_one()), never
forming a destination read. -0.0 counts as zero; NaN stays on the read
path.
- Add UpdatePlan::execute_uninit and ErasedUpdatePlan::execute_uninit
(beta implicitly zero) that fully initialize every reachable slot,
following the existing *_uninit validation-before-write convention.
- Tests: typed and erased f32/f64/c64, contiguous/permuted, NaN-poisoned
destinations and poisoned MaybeUninit, serial and two-worker, -0.0 and
NaN beta. alloc_matrix asserts zero allocations for the uninit replay.
shinaoka
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October 17, 2026 11:57
Repository rules reviewRepository rules review (ddbe17bcb64969a062d2a052f61afbdec9cd18c3...62d259f3e4e99e871082e660e2f78abfd668f7ea) Verdict: pass Findings: - [warn] llm-skipped (External LLM Review) <unknown>: External LLM review was skipped External LLM review is permanently disabled; deterministic checks only. |
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* chore: release strided 0.6.0 (all crates) Allocation-free API (#316, #306) and UpdatePlan beta=0 (#317). Versions unified on the workspace at 0.6.0. Release note: docs/worklogs/2026-10-17-release-0.6.0.md. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> * bench(basic): set the S3 smoke thresholds from the slowest machine seen The GitHub-hosted runner measured S3a 1.87 / S3b 3.15 after #317 made the beta == 0 compiled baseline write-only; the reference host measures ~1.5 / ~2.2. Initial thresholds 2.5 / 4.0, to be tightened from CI history (#306). Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> --------- Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
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Follow-up to #316, found by the tcontract 0.3 pre-review (tcontract-rs#121).
UpdatePlan::executereplayed*dst = alpha * value + beta * *dstunconditionally. BLAS semantics require that beta == 0 does not read the destination; otherwise NaN or garbage in D leaks through0 * NaN = NaN, and a fresh output can never be represented as uninitialized.Zero::is_zero, so -0.0 counts as zero and a NaN beta keeps the read path),UpdatePlanandErasedUpdatePlantake a write-only replay (*dst = alpha * value). The bounds gainZero + One + PartialEq.UpdatePlan::execute_uninitandErasedUpdatePlan::execute_uninitwrite intoMaybeUninitstorage with beta implicitly 0. Validation and the overlap check happen before any write, and every reachable slot is initialized.execute_uninitinitializes every slot, including a layout with holes.alloc_matrixarms assert 0 allocations at rank 1..=8.copy_plan.rs97.2%,erased.rs87.6%, all 48 files pass.cargo test --profile ci, the parallel lane and--no-default-featuresare green.This lands before the 0.6.0 release PR.
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