packed/cascade: pin that the two stroke packers agree at 2048 bytes by AdaWorldAPI · Pull Request #354 · AdaWorldAPI/ndarray

AdaWorldAPI · 2026-10-10T16:09:37Z

What this PR now contains

A test, stroke_split_equals_the_cascade_split_at_2048, pinning that hpc::packed::PackedDatabase and hpc::cascade::PackedDatabase split a 2048-byte row into the same strokes (128 / 384 / 1536). The test fails if cascade's split point moves.
Doc cross-links between the two packers, and a note that cam_pq::PackedDatabase shares only the name.
A blackboard entry recording this.

Withdrawn

This PR first added mask_row_window and bit_sliced_weighted_count. Both have been reverted out of the branch:

mask_row_window took a signed i64 column.
bit_sliced_weighted_count returned a signed sum over positive and negative planes.

Signed masks do not belong on this facade. The use case they were written for, a 256×256 tile, is the palette256 × palette256 address (u8:u8). That address is answered by the 256×256 distance and compose tables, not by geometric windows.

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packed::PackedDatabase (fixed 128/384/1536) and cascade::PackedDatabase (width-derived split) lay out the same strokes for 2048-byte rows; a test pins it. Doc cross-links name the third, unrelated cam_pq type. Not merged: the two types have different query paths and the first carries an index. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EFw2WdKr1oxvaKCJC2ua2R

…weighted_count R-MHB-1 prerequisites. mask_row_window reads up to 64 bits of one row of a row-major packed grid at any column; a window that leaves its row is refused (None) by default, or zero-filled on request, and never reads a neighbouring row. bit_sliced_weighted_count is the bit-sliced weighted popcount (arm F's row kernel): sum_b 2^b (popcnt(w & pos_b) - popcnt(w & neg_b)), exact for integer weights, no weight lane. Reference-tested (20k random windows, 2k weighted rows) plus an edge test that a flat bit offset would fail. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EFw2WdKr1oxvaKCJC2ua2R

… one Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EFw2WdKr1oxvaKCJC2ua2R

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.claude/blackboard.md

📝 Walkthrough

Walkthrough

The change adds public SIMD operations for extracting row windows and computing signed weighted counts. It also clarifies documentation for packed database types and adds a test comparing their stroke layouts.

Changes

SIMD Masking Operations

Layer / File(s)	Summary
Masking operations and exports `src/simd_masking_ops.rs`, `src/simd.rs`	Adds `WindowEdge`, `mask_row_window`, and `bit_sliced_weighted_count`, and re-exports them from `src/simd.rs`. Tests cover boundary behavior, row isolation, and weighted counts.

Packed Database Clarifications

Layer / File(s)	Summary
Packed database documentation and layout test `.claude/blackboard.md`, `src/hpc/cascade.rs`, `src/hpc/packed.rs`	Clarifies the distinctions between the packed database types and their layouts. Adds a test that compares stroke splits and slices for five generated 2048-byte rows.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Feature

Suggested reviewers: claude

Merge Risk: 🔵 Low · up to 24ad7

The new public SIMD helpers do not follow the project's required API contract. Extreme window coordinates can also panic or return the wrong result. Neither problem affects existing behavior, so the change is mergeable, but the owners should resolve both or explicitly accept them.

Pre-merge checks | 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage		Docstring coverage is 90.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 10 functions across 4 files. (1 skipped: 1 …
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly describes the added test that verifies the packed and cascade stroke packers agree at 2048-byte rows. It covers a significant change in the pull request and uses concise, specific wo…

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_{A rabbit counts each bit in rows,
And checks where every window goes.
Three packed names now stand apart,
Their strokes align, each tested part.
Hop, hop—the checks are done!}

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Inline comments:
Review comments at @src/simd_masking_ops.rs:
- Line 9940: Update mask_row_window and bit_sliced_weighted_count to follow the
W1a consumer contract, replacing their scalar-only free-function implementations
with typed-wrapper APIs, closure-parameterized batch primitives,
AVX*/NEON/scalar backends, and parity tests. In src/simd_masking_ops.rs at lines
9940 and 9995, implement the corresponding operations; in src/simd.rs at lines
838 and 878, replace the free-function re-exports with the conforming public
APIs.
- Around line 9946-9948: Replace the unchecked width calculation and
end-coordinate addition with checked arithmetic. In the surrounding window
operation, route unrepresentable coordinates through the existing WindowEdge
handling so Refuse returns None and ZeroFill preserves its out-of-row behavior.

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.claude/blackboard.md
src/hpc/cascade.rs
src/hpc/packed.rs
src/simd.rs
src/simd_masking_ops.rs

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col + len overflowed for col near i64::MAX (a panic with overflow checks, a wrapped end without them, which let Refuse accept an out-of-row window). The end is now checked and the width saturates; an unrepresentable end is simply not inside the row, so both edge policies still apply. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EFw2WdKr1oxvaKCJC2ua2R

Three arms over a 64k-cell presence tile, every anchor: per-tap u16 direct addressing (reference), per-cell windows via ndarray's mask_row_window + bit_sliced_weighted_count, and row-direct bit-parallel (shifted 256-bit rows into bit-sliced counters). Coordinates are u8 summed in u16, taps anchored top-left, so nothing but the weights is signed. Compiles and passes clippy -D warnings; NOT yet run. Needs ndarray's mask_row_window (AdaWorldAPI/ndarray#354) on the base before a PR. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EFw2WdKr1oxvaKCJC2ua2R

This reverts commit df7abe0.

…_sliced_weighted_count" This reverts commit a386c9e.

… pin Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EFw2WdKr1oxvaKCJC2ua2R

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claude added 3 commits October 10, 2026 16:03

blackboard: R-MHB-1 prerequisites; PackedDatabase is three types, not…

24ad716

… one Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EFw2WdKr1oxvaKCJC2ua2R

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Comment thread src/simd_masking_ops.rs Outdated

Comment thread src/simd_masking_ops.rs Outdated

AdaWorldAPI marked this pull request as draft October 10, 2026 16:26

claude added 3 commits October 10, 2026 16:29

Revert "mask_row_window: no overflow at extreme columns or widths"

547b8aa

This reverts commit df7abe0.

Revert "simd: mask_row_window (2-D window, refuse or zero-fill) + bit…

4a6dd93

…_sliced_weighted_count" This reverts commit a386c9e.

blackboard: withdraw the signed window helpers; keep the stroke-split…

5cc83b4

… pin Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EFw2WdKr1oxvaKCJC2ua2R

AdaWorldAPI changed the title ~~simd: R-MHB-1 window + bit-sliced weighted count; pin the PackedDatabase stroke split~~ packed/cascade: pin that the two stroke packers agree at 2048 bytes Oct 10, 2026

AdaWorldAPI marked this pull request as ready for review October 10, 2026 16:59

AdaWorldAPI merged commit 8afa92d into master Oct 10, 2026
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AdaWorldAPI mentioned this pull request Oct 13, 2026

cpu_guard test: probe a libc symbol no sanitizer interposes (fixes cargo-careful on master) #362

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packed/cascade: pin that the two stroke packers agree at 2048 bytes - #354

packed/cascade: pin that the two stroke packers agree at 2048 bytes#354
AdaWorldAPI merged 7 commits into
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