feat: add C implementation for stats/base/dists/signrank/quantile

[nirmaljb]

Resolves #3885 .

Description

What is the purpose of this pull request?

This pull request:

• Adds a C implementation of the signrank quantile function.
• Includes benchmarks for the C implementation.
• Provides examples demonstrating the usage of the signrank quantile in C.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [RFC]: Add C implementation for @stdlib/stats/base/dists/signrank/quantile #3885

Questions

Any questions for reviewers of this pull request?

No.

Other

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No.

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

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{{TODO: add disclosure if applicable}}

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@stdlib-js/reviewers

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/signrank/quantile	$\color{green}371/371$ $\color{green}+0.00%$	$\color{green}47/47$ $\color{green}+0.00%$	$\color{green}5/5$ $\color{green}+0.00%$	$\color{green}371/371$ $\color{green}+0.00%$

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

[nirmaljb]

/stdlib update-copyright-years

[nirmaljb]

The test is stuck at test.native.js test with large n values (up to 150) from the fixtures. The recursive weights function has O(2^n) complexity, making it extremely slow.
Should I reduce the value of N to compensate for it?

[nirmaljb]

Hello Maintainer, just a heads up.

1. I reduced the C benchmark constraints as well as test.native.js constraints to a lesser ( n <= 20 ) value from the fixture because the tests were stuck, simply because the recursive weights function has O(2^n) complexity, making it extremely slow.
2. I removed the test case that checks whether the value of N is an integer or not. Because in main.c int32_t truncates 4.8 to 4 (valid positive integer), so the function returns a valid result.

[Planeshifter]

Thanks for the PR! Left round of feedback.

[Planeshifter]

Remove the dead NaN/finite checks on int32_t and match signrank/pdf with just n <= 0. Also drop the unused is_finite and is_positive_integer from includes and manifest.json. We do not need runtime validation when n is appropriately typed already.

[Planeshifter]

n * ( n + 1 ) overflows in int32_t for n >= 46341. Let's cast:

Suggested change

	return ( n * ( n + 1 ) ) / 2;
	return ( (double)n * ( (double)n + 1.0 ) ) / 2.0;

[Planeshifter]

Suggested change

	* @returns evaluated quantile function
	* @return evaluated quantile function

[Planeshifter]

We can drop the blank line between the closing */ and the function definition.

Suggested change

	double stdlib_base_dists_signrank_quantile( const double p, const int32_t n ) {
	double stdlib_base_dists_signrank_quantile( const double p, const int32_t n ) {

[Planeshifter]

Use a float literal — function returns double.

Suggested change

	return 0;
	return 0.0;

[Planeshifter]

Missing spaces inside the parens.

Suggested change

	var quantile = tryRequire(resolve(__dirname, './../lib/native.js'));
	var quantile = tryRequire( resolve( __dirname, './../lib/native.js' ) );

[Planeshifter]

Missing spaces inside parens.

Suggested change

	'skip': (quantile instanceof Error)
	'skip': ( quantile instanceof Error )

[Planeshifter]

Missing space before closing ).

Suggested change

	if ( n[ i ] >= 20) {
	if ( n[ i ] >= 20 ) {

[Planeshifter]

This is a quantile, not a PDF — label should be Q(p;n) (matches the JS examples section).

Suggested change

	printf( "p: %lf, n: %d, f(x;n): %lf\n", p, n, y );
	printf( "p: %lf, n: %d, Q(p;n): %lf\n", p, n, y );

[Planeshifter]

Same thing here — should be Q(p;n), not f(x;n).

Suggested change

	printf( "p: %lf, n: %d, f(x;n): %lf\n", p, n, y );
	printf( "p: %lf, n: %d, Q(p;n): %lf\n", p, n, y );