simd: PowerSums::checked_merge + CrossPowerSums fold; CovHighD::from_symmetric_fn by AdaWorldAPI · Pull Request #338 · AdaWorldAPI/ndarray

AdaWorldAPI · 2026-10-04T17:43:32Z

Summary

PowerSums::checked_merge: combine per-chunk power sums exactly; refuses (returns None) instead of wrapping.
CrossPowerSums { n, Σx, Σy, Σx², Σy², Σxy } and masked_group_cross_power_sums_i32{,_via,_pair} on the existing visitor walker, re-exported from simd.
pillar::cov_high_d: CovHighD::from_symmetric_fn, public get, and a sandwich test with a non-identity M.

Consumed by lance-graph branch ccr-1d39fce9-gdgy6k (mask-risc grouped moments / cross moments terminals, jc ANOVA / Pearson / OLS from moments, perturbation-sim angle covariance). That PR depends on this one.

Tests

Chunked merge equals the one-pass result; a merge past the width bound refuses.
Cross moments across key forms (lane / via / pair) agree with a reference fold.
Sandwich test against a non-identity matrix.

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https://claude.ai/code/session_01X1YcYMRSFvfczXoP748wtB

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Summary by CodeRabbit

New Features
- Added tools for constructing and reading symmetric covariance matrices.
- Added grouped analysis of paired values, including counts, individual totals, squared totals, and cross-products. Results can be combined safely, with overflow reported rather than silently accepted.
- Added access to these paired-value calculations through the SIMD masking interface.
Bug Fixes
- Improved validation coverage for covariance calculations and grouped statistics, including overflow handling and mismatched input lanes.

… wrapping The keyed fold wraps, as the whole family does. A caller that tiles a population and combines the per-tile results needs the opposite: exact addition that refuses past the documented 2^32-rows-per-group bound. Each field is checked independently. Tests: two-chunk merge equals the one-pass fold at word, mid-word and end splits in both orders; three-way associativity; per-field refusal. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01X1YcYMRSFvfczXoP748wtB

… walker CrossPowerSums is the bivariate sibling of PowerSums: same widths for the marginals (u128 square sums), plus a signed i128 Σxy. x()/y() return the marginals exactly as the univariate fold produces them; checked_merge combines chunks without wrapping. masked_group_cross_power_sums_i32 with _via / _pair share one fold, as the power-sum family does. Tests: i128/u128 longhand oracle on resident and VIA keys at three mask densities, marginals equal the univariate fold (resident and pair), chunk merges in both orders, exactness at the i32 extremes, per-field merge refusal. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01X1YcYMRSFvfczXoP748wtB

…n-identity M CovHighD had no public way to be built from data (only identity() and the private zero()), so a consumer could not push a real covariance through sandwich without re-spelling the packed lower-triangle index. from_symmetric_fn reads the lower triangle once; get is made public. Every existing sandwich test used M = I, where a transposed or mis-indexed product is invisible. Adds a dense M·Σ·M triple-product check for a non-identity symmetric M. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01X1YcYMRSFvfczXoP748wtB

coderabbitai · 2026-10-04T17:43:40Z

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📒 Files selected for processing (3)

src/hpc/pillar/cov_high_d.rs
src/simd.rs
src/simd_masking_ops.rs

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📝 Walkthrough

Walkthrough

The changes add symmetric covariance construction and public lookup, checked merging for power statistics, and masked grouped cross-power-sum operations for three key formats.

Changes

Symmetric covariance

Layer / File(s)	Summary
Symmetric access and construction `src/hpc/pillar/cov_high_d.rs`	`CovHighD::get` is public. `from_symmetric_fn` fills the lower triangle and uses symmetry for other reads. Tests cover the constructor and a dense reference for `sandwich`.

Masked grouped cross-power sums

Layer / File(s)	Summary
Statistic types and checked merging `src/simd_masking_ops.rs`	`PowerSums` and `CrossPowerSums` gain checked merging. `CrossPowerSums` exposes its x and y marginals as `PowerSums`. Tests cover chunk merging and overflow handling.
Joint folds and validation `src/simd_masking_ops.rs`, `src/simd.rs`	Resident-key, indirect-key, and composite-key folds accumulate joint statistics. The SIMD facade exports the new operations and type. Tests compare results with wide references and univariate folds, and cover merging, extreme values, and mismatched lane lengths.

Priority: ⬇️ Low

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

Change: Feature

Suggested reviewers: claude

Merge Risk: ⚪ Minimal · up to a62ad

No identified issue blocks merging after normal checks.

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Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly names the checked merge, cross-power-sum fold, and symmetric covariance constructor added by the pull request.
Docstring Coverage	✅ Passed	Docstring coverage is 96.55% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 29 functions across 3 files.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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_{A rabbit checks the sums at dawn
Two lanes hop where masks are drawn
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cursor · 2026-10-04T17:43:47Z

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coderabbitai · 2026-10-04T17:56:45Z

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claude added 3 commits September 30, 2026 22:42

AdaWorldAPI mentioned this pull request Oct 4, 2026

mask-risc + jc: grouped power-sums / cross-power-sums terminals; ANOVA, Pearson, OLS from power sums; perturbation-sim angle_cov AdaWorldAPI/lance-graph#1323

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AdaWorldAPI marked this pull request as ready for review October 4, 2026 17:56

AdaWorldAPI merged commit b574841 into master Oct 4, 2026
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simd: PowerSums::checked_merge + CrossPowerSums fold; CovHighD::from_symmetric_fn - #338

simd: PowerSums::checked_merge + CrossPowerSums fold; CovHighD::from_symmetric_fn#338
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