test: migrate stats/base/dists/discrete-uniform/quantile to ULP-based assertions

[kgryte]

Resolves a part of #11352.

Description

What is the purpose of this pull request?

This pull request:

• migrates the tests for stats/base/dists/discrete-uniform/quantile from relative tolerance testing to ULP difference testing, per [RFC]: Migrate math/base/special packages from relative tolerance testing to ULP difference testing (tracking issue) #11352.

The computed delta/tol comparisons in the fixture loops of test/test.quantile.js, test/test.factory.js, and test/test.native.js are replaced with isAlmostSameValue( y, expected[ i ], 0 ) assertions, and the now-unused @stdlib/math/base/special/abs and @stdlib/constants/float64/eps requires are dropped in favor of @stdlib/assert/is-almost-same-value. No other test cases were touched; the exact comparisons elsewhere in these files are unchanged. test/test.js contains no tolerance-based assertions and is therefore unmodified.

The ULP bound is the measured minimum over each full fixture set:

Fixture	Measured max ULP diff	ULP bound
fixtures/julia/small_range.json	0	0
fixtures/julia/medium_range.json	0	0
fixtures/julia/large_range.json	0	0

Each fixture set contains 1000 cases. Starting from a loose bound and tightening, every one of the 3000 cases is bit-identical to the Julia-generated expected value for both implementations under test (lib/main.js and lib/factory.js), so the measured maximum ULP difference is 0 and test.factory.js uses the same bound as test.quantile.js. Because maxULP = 0 requires isSameValue equality, it is the tightest integer bound attainable and no smaller value exists to check.

This result is expected: the quantile function evaluates a + floor( p*(b-a+1) ), which, for the integer supports exercised by the fixtures, is exactly representable in double precision.

The same bound holds for the C implementation. The native add-on was built locally (node-gyp rebuild) so that test/test.native.js actually runs rather than being skipped, and all 3007 of its assertions pass at 0 ULP. As a cross-check against FMA/arch sensitivity, the C expression was additionally evaluated over the same 3000 fixture cases in a standalone harness compiled both at -O2 and at -O3 -march=native -ffp-contract=fast; both produced bit-identical results for every case.

The suite was run twice at the final bound, with identical results both times (3016 + 3012 + 3 + 3007 assertions passing, 0 failing).

Note that the previous bound was 1.0 * EPS in all nine fixture loops; the 0 ULP bound is strictly tighter.

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.

• make lint-javascript-tests TESTS_FILTER=".*/stats/base/dists/discrete-uniform/quantile/.*" is clean.
• The idiom mirrors the already-converted sibling packages stats/base/dists/erlang/quantile and stats/base/dists/chisquare/quantile.
• make lint-editorconfig-files could not run in this environment, as the editorconfig-checker binary could not be downloaded. The changed lines were checked by hand for tab indentation, trailing whitespace, line endings, and a final newline.

Checklist

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

• Read, understood, and followed the contributing guidelines.

AI Assistance

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• Yes
• No

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• 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 written by Claude Code, which also measured the minimum ULP bound empirically and ran the tests and linter.

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https://claude.ai/code/session_01VdWTZQyfuCaFizioXQ6JKf

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Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/discrete-uniform/quantile	$\\color{green}299/299$ $\\color{green}+100.00\\%$	$\\color{green}27/27$ $\\color{green}+100.00\\%$	$\\color{green}4/4$ $\\color{green}+100.00\\%$	$\\color{green}299/299$ $\\color{green}+100.00\\%$

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