test: migrate constants/float16/half-ln-two to ULP-based assertions

[kgryte]

Resolves a part of #11352.

Description

What is the purpose of this pull request?

This pull request:

• migrates the constants/float16/half-ln-two test suite 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.

Specifically, this pull request:

• adds the @stdlib/number/float16/base/assert/is-almost-same-value import and removes the now-unused @stdlib/math/base/special/absf and @stdlib/constants/float16/eps imports.
• removes the delta/tol computations (and the corresponding var delta;/var tol; declarations) from the export equals 0.5*lnf(2) test case.
• replaces t.ok( delta <= tol, ... ) with t.strictEqual( isAlmostSameValue( v, FLOAT16_HALF_LN2, 0 ), true, 'returns expected value' );.

Only test/test.js is modified; the package has no test/test.native.js. No other test cases were touched, and the existing exact comparisons (t.strictEqual on the typeof check and on the literal constant value) were left as-is.

The conversion mirrors, line for line, the already-merged migrations of the two sibling packages for this exact same constant: constants/float32/half-ln-two (#16071) and constants/float64/half-ln-two (#16098). The import follows the existing precision convention established by those packages: the float32 package uses the single-precision @stdlib/number/float32/base/assert/is-almost-same-value, the float64 package uses the double-precision @stdlib/assert/is-almost-same-value, and so this pull request uses the half-precision @stdlib/number/float16/base/assert/is-almost-same-value, since the value under test is a half-precision constant and ULP distance must therefore be measured in half-precision space.

ULP bound

Test case	Measured ULP difference	Final ULP bound
export equals 0.5*lnf(2)	0	0

float64ToFloat16( 0.5 * lnf( 2.0 ) ) and FLOAT16_HALF_LN2 are bit-identical, so the measured ULP difference is 0, which is also the floor (isAlmostSameValue with maxULP === 0 reduces to isSameValue). The bound therefore cannot be tightened further. This matches the 0 bound accepted for the corresponding test case in both constants/float32/half-ln-two and constants/float64/half-ln-two, and is strictly tighter than the relative tolerance it replaces: the old tol = EPS * FLOAT16_HALF_LN2 evaluated to ≈3.386e-4, whereas one half-precision ULP at this magnitude is 2^-2 * EPS16 ≈ 2.441e-4, so the previous assertion admitted more than 1 ULP of error.

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 test TESTS_FILTER=".*/constants/float16/half-ln-two/.*" passes 4/4. The suite was run three times at the final bound with identical results, confirming determinism (no FMA/arch-dependent variation in this environment). The test suite uses no PRNG, so the fixture values are fixed by construction.
• The assertion was separately confirmed to be live: perturbing the constant by a single half-precision ULP is rejected at maxULP === 0 and accepted at maxULP === 1.
• make eslint-tests TESTS_FILTER=".*/constants/float16/half-ln-two/.*" passes cleanly, as does make lint-license-headers-files for the changed file.
• The lint-editorconfig-files target was not run in this environment, as it downloads the editorconfig-checker binary from a host that was not reachable from the sandbox. The file was instead verified programmatically against .editorconfig: LF line endings, valid UTF-8, tab indentation (no space-indented lines), no trailing whitespace, and a single final newline.

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 selected the package at random from the remaining unconverted candidates, studied the already-merged constants/float32/half-ln-two and constants/float64/half-ln-two migrations as prior art, performed the test conversion, and determined the minimum ULP bound empirically by measuring the observed ULP difference and confirming that the bound is both minimal and the hard floor.

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@stdlib-js/reviewers

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Generated by Claude Code

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
constants/float16/half-ln-two	$\\color{green}50/50$ $\\color{green}+100.00\\%$	$\\color{green}1/1$ $\\color{green}+100.00\\%$	$\\color{green}0/0$ $\\color{green}+100.00\\%$	$\\color{green}50/50$ $\\color{green}+100.00\\%$

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