[N-01] Gaussian math audit

[ericnordelo]

Summary by CodeRabbit

• Documentation
  • Expanded technical documentation for probability distribution calculations.
  • Added details about possible error conditions and validation checks.
  • Clarified signed-value representation, magnitude limits, and canonical zero handling.
  • No functional behavior or public interfaces were changed.

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Review details

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: f706c6d4-fe68-4b24-a5a3-c26ac11ab35d

📥 Commits

Reviewing files that changed from the base of the PR and between 59db76d and 2add14a.

📒 Files selected for processing (3)

• math/fixed_point/sources/internal/cdf.move
• math/fixed_point/sources/internal/inverse_cdf.move
• math/fixed_point/sources/internal/pdf.move

📝 Walkthrough

Walkthrough

Documentation-only updates clarify SignedScaled256 representation invariants and enumerate abort conditions for CDF, PDF, and inverse-CDF rational evaluators. No executable logic, fields, signatures, or control flow changed.

Changes

Fixed-point documentation

Layer / File(s)	Summary
Signed-magnitude representation documentation math/fixed_point/sources/internal/horner.move	Documents magnitude bounds, sign handling, canonical zero, and the mag accessor.
Evaluator abort-condition documentation math/fixed_point/sources/internal/cdf.move, math/fixed_point/sources/internal/pdf.move, math/fixed_point/sources/internal/inverse_cdf.move	Documents rational-integrity aborts and the inverse-CDF tail logarithm abort condition.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Possibly related PRs

• OpenZeppelin/contracts-sui#410: Related PDF/CDF evaluator documentation for the same rational-evaluation abort conditions.
• OpenZeppelin/contracts-sui#431: Related changes to rational-evaluation paths and their documented abort conditions.

Suggested reviewers: 0xneshi, immrsd, bidzyyys

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	No PR description was provided, so the required template fields and checklist are missing.	Add the template sections, including the issue reference, a brief change summary, and the Tests/Documentation/Changelog checklist.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title matches the PR's Gaussian math audit docs changes, though it is broad rather than specific.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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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• Create PR with unit tests
• Commit unit tests in branch fix/gaussian-audit-N-01

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.51%. Comparing base (f880455) to head (2add14a).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #474      +/-   ##
==========================================
+ Coverage   96.45%   96.51%   +0.05%     
==========================================
  Files          34       34              
  Lines        3414     3411       -3     
  Branches      799      799              
==========================================
- Hits         3293     3292       -1     
  Misses         73       73              
+ Partials       48       46       -2     

Flag	Coverage Δ
contracts/access	65.46% <ø> (ø)
contracts/allowance	52.40% <ø> (ø)
contracts/finance	26.66% <ø> (ø)
contracts/timelock	54.32% <ø> (ø)
contracts/utils	44.09% <ø> (ø)
math/core	86.89% <ø> (+0.14%)	⬆️
math/fixed_point	63.62% <ø> (-0.08%)	⬇️

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@math/fixed_point/sources/internal/cdf.move`:
- Around line 98-105: Update the abort documentation for eval_rational and the
corresponding CDF, PDF, and inverse-CDF functions at
math/fixed_point/sources/internal/cdf.move:75-79 and 98-105,
math/fixed_point/sources/internal/pdf.move:65-69 and 87-94, and
math/fixed_point/sources/internal/inverse_cdf.move:75-82 and 128-135. Add the
inherited vector index out-of-bounds abort for mismatched magnitude/sign pairs,
noting it is unreachable with committed tables, and split EInternalNumNegative
and EInternalDenNonPositive into distinct bullets.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 9d6d20a4-c237-467a-8d0c-c026a82dcd82

📥 Commits

Reviewing files that changed from the base of the PR and between f880455 and 59db76d.

📒 Files selected for processing (4)

• math/fixed_point/sources/internal/cdf.move
• math/fixed_point/sources/internal/horner.move
• math/fixed_point/sources/internal/inverse_cdf.move
• math/fixed_point/sources/internal/pdf.move

[bidzyyys]

LGTM