[AtharvaPatange]

Resolves part of #14819.

Description

What is the purpose of this pull request?

This pull request:

• Adds a native C implementation for blas/ext/base/ndarray/dtriu.
• Retains the JavaScript fallback when the native addon is unavailable.
• Adds native tests, C examples, and C benchmarks.
• Uses a zero-dimensional int32 ndarray for the diagonal offset k.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [RFC]: add C implementations for blas/ext/base/ndarray packages #14819

Questions

Any questions for reviewers of this pull request?

I’ve added allocation and ndarray metadata checks (NULL checks) in dtriu/benchmark.length.c, similar to the existing ztriu implementation. Should I keep these checks and the related changes, or would you prefer that I strictly follow the existing dtril benchmark implementation for consistency?

Other

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

The int32 scalar approach follows the discussion in #14471 .

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.".

AI assistance was used to update tests and benchmarks, and prepare documentation.

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Coverage Report

Package	Statements	Branches	Functions	Lines
blas/ext/base/ndarray/dtriu	$\\color{green}226/226$ $\\color{green}+0.00\\%$	$\\color{green}7/7$ $\\color{green}+0.00\\%$	$\\color{green}2/2$ $\\color{green}+0.00\\%$	$\\color{green}226/226$ $\\color{green}+0.00\\%$

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