revert(reduction): the concurrent member reads, and correct what they claimed - #122
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… claimed Measured properly, on both source regimes, with the peak sampled rather than assumed. A five-case fold of Clip + Resample: h5 (bounded reads) 1 reader 1.04 s / 2.8 members 4 readers 1.76 s / 6.2 members nii.gz (full decode) 1 reader 6.85 s / 2.5 members 4 readers 5.51 s / 4.9 members On a store that serves regions -- the common case -- overlapping the reads is 73% SLOWER for 2.2x the peak. Where it does pay, it buys 1.24x for 2x the peak, and that peak is charged nowhere: ReductionPlan.peak_bytes counts the members and the operator's multiple, not the chain replicas running beside them. A tight budget went to an OOM on a promise the plan said it was keeping. The finding behind it stands (nothing overlaps, five cores of twenty-four busy); the right shape is a one-region read-ahead counted in the budget, not a pool of four chains. Also corrected, because both would have shipped false: the changelog announced a HEAVIER Median where the selection networks make it lighter at two, three and five members, and AGENTS.md still described Median as stacking and sorting at a flat 4.0.
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Included review availability: 2 reviews are currently available. Your included PR review attempts over the past 7 days set your current allowance at 3 reviews per hour. 📝 WalkthroughWalkthroughThe change removes concurrent reduction-member reads and documents sequential folding. It updates Median’s cohort-dependent algorithms and memory planning. Streaming documentation now records revised locality and augmentation behavior, including affine region streaming and full-volume fallback cases. ChangesReduction execution and planning
Streaming locality documentation
Estimated code review effort: 2 (Simple) | ~10 minutes Merge Risk: ⚪ Minimal · up to This PR reverts the concurrent member-read optimization and corrects related performance and documentation claims; no actionable merge-blocking risk remains beyond normal checks and review. Possibly related PRs
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✨ Finishing Touches🧪 Generate unit tests (beta)
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Inline comments:
In `@AGENTS.md`:
- Line 68: Update the Median working_multiple documentation in AGENTS.md to
include the two-member case with its documented value of 1.5, while preserving
the existing values for three, four, five, and larger cohorts.
In `@docs/source/concepts/streaming.md`:
- Line 136: Update the POINTWISE locality-table entry for TensorCast to specify
that it applies only to lossless target casts, matching the streaming rule
described earlier; leave lossy casts excluded from the unconditional pointwise
classification.
In `@docs/source/reference/components/augmentations.md`:
- Around line 51-52: Update the lifecycle rule for composed region augmentations
to state that region stages compose and stream their required windows through
the affine transform, rather than loading the whole volume. Keep the behavior
consistent with the Rotate and Scale entries and the documented affine streaming
contract.
In `@docs/source/troubleshooting.md`:
- Around line 106-107: Update the streaming documentation list containing
Resample, Padding, Mask, Dilate, and Gradient so Mask is not classified as a
region kind; either describe the list as streamable transforms or remove Mask,
consistent with its POINTWISE classification in the streaming concepts
documentation.
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AGENTS.mdCHANGELOG.mddocs/source/concepts/streaming.mddocs/source/config_guide/transform.mddocs/source/reference/components/augmentations.mddocs/source/troubleshooting.mdkonfai/data/case_reduction.pytests/unit/test_case_reduction.py
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- AGENTS.md lists Median's two-member multiple beside the others. - The locality table carries TensorCast's condition the prose already stated: only a target that holds every value streams. - The augmentation page said a region draw and a region transform in one chain load the volume; they compose, as the streaming page says and the planner does. - Mask is not a region kind: it streams as a pointwise stage that reads its companion mask by region.
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What a full audit of
mainturned up before the v1.8.1 tag, and what it takes back out.The revert: concurrent member reads
I added them hours ago on one number (2.39 s → 0.97 s). Measured properly, on both source regimes,
with the peak sampled at 4 ms instead of assumed — five-case fold,
Clip+Resample:On a store that serves regions — the common case — overlapping is 73% slower for 2.2× the peak.
Where it does pay it buys 1.24× for 2× the peak, and that peak is charged nowhere:
ReductionPlan.peak_bytescounts the members and the operator's multiple, not the chain replicasrunning beside them. A tight budget went to an OOM on a promise the plan said it was keeping.
The finding behind it stands (nothing overlaps, five cores of twenty-four busy). The right shape is a
one-region read-ahead counted in the budget, not a pool of four chains. Engine, test and
changelog entry all come back out.
Two claims that would have shipped false
Median("four buffers instead of two") where the selectionnetworks make it lighter at two, three and five members. Rewritten with the real figures per
cohort size.
AGENTS.md§4 still describedMedianas "stacks, sorts and interpolates copies, measured 4.0".Rewritten around
working_multiple_for.Documentation put back in step with the code
Debt from #112, which made draws and stages stream without updating the tables:
reference/components/augmentations.mdsaid no stream for a free-angleRotate,Scale,NoiseandCutOUT. The code declares REGRID, REGRID, POINTWISE, POINTWISE(
augmentation.py:464,720,1007).concepts/streaming.mdlistedMaskasSLABand said it loads the volume, wheretransform.py:2194declares POINTWISE and reads the mask by region; putPadding'sreflect/replicateatWHOLE_VOLUMEwheretransform.py:997returns REGRID unconditionally;and contradicted itself between two paragraphs of the same page.
troubleshooting.mdrepeated the stale version.config_guide/transform.mdstill saidMedian"stacks and sorts".The
Maskdraw and theMasktransform share a name and not a verdict, which is what made thiseasy to get wrong; the page now says which is which.
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