[kgryte]

Resolves a part of #11352.

Description

What is the purpose of this pull request?

This pull request:

• migrates the tests for math/base/special/fast/atanh from relative tolerance testing (delta <= EPS * abs( expected )) to ULP difference testing using @stdlib/assert/is-almost-same-value.

Changes are confined to test/test.js and test/test.native.js. No source, documentation, benchmark, or fixture files were touched, and no test cases were added, removed, or reordered.

The measured minimum ULP bounds (the maximum observed ULP difference across the full fixture set, i.e. the smallest integer for which every case passes) are:

Test case	Previous tolerance	ULP bound	Fixture size
negative values (fixtures/julia/negative.json)	500.0 * EPS * abs( expected )	468	2003
positive values (fixtures/julia/positive.json)	650.0 * EPS * abs( expected )	655	2003

Each bound was tightened to the minimum: 468 and 655 pass for every fixture value, while 467 and 654 do not.

The same bounds apply to both test.js and test.native.js. The native add-on was built locally, and the C implementation was verified to produce bit-identical results to the JavaScript implementation across both fixture files (max ULP difference of 468 and 655, respectively), so no JS/C divergence adjustment was required.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [RFC]: Migrate math/base/special packages from relative tolerance testing to ULP difference testing (tracking issue) #11352

Questions

Any questions for reviewers of this pull request?

No.

Other

Any other information relevant to this pull request? This may include screenshots, references, and/or implementation notes.

Verification performed:

• make test TESTS_FILTER=".*/math/base/special/fast/atanh/.*" — 6015 passing / 0 failing in test.js and 6015 passing / 0 failing in test.native.js. The suite was run twice at the final ULP values with identical results (no FMA/architecture-dependent variation observed).
• ESLint with etc/eslint/.eslintrc.tests.js — clean for both changed files.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• Read, understood, and followed the contributing guidelines.

AI Assistance

When authoring the changes proposed in this PR, did you use any kind of AI assistance?

• Yes
• No

If you answered "yes" above, how did you use AI assistance?

• Code generation (e.g., when writing an implementation or fixing a bug)
• Test/benchmark generation
• Documentation (including examples)
• Research and understanding

Disclosure

If you answered "yes" to using AI assistance, please provide a short disclosure indicating how you used AI assistance. This helps reviewers determine how much scrutiny to apply when reviewing your contribution. Example disclosures: "This PR was written primarily by Claude Code." or "I consulted ChatGPT to understand the codebase, but the proposed changes were fully authored manually by myself.".

This PR was authored by Claude Code running as an unattended scheduled task. It studied the migration guidance in #11352 and the already-migrated sibling packages (math/base/special/fast/asinh, math/base/special/fast/acosh) to mirror the established idiom, measured the ULP bounds empirically against the fixtures, and ran the test suite and linter locally.

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@stdlib-js/reviewers

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Generated by Claude Code

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/fast/atanh	$\\color{green}186/186$ $\\color{green}+100.00\\%$	$\\color{green}10/10$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}186/186$ $\\color{green}+100.00\\%$

The above coverage report was generated for the changes in this PR.