NIKX-Tech/numx

linalg: QR decomposition (Householder)

Open

#82 opened on Jul 11, 2026

View on GitHub
 (0 comments) (0 reactions) (0 assignees)C (1 fork)github user discovery
enhancementgood first issue

Repository metrics

Stars
 (4 stars)
PR merge metrics
 (PR metrics pending)

Description

Add numx_qr_decompose to the linalg module: QR decomposition via Householder reflections, bounded by NUMX_MAX_MAT_ROWS/NUMX_MAX_MAT_COLS like the rest of linalg (see numx_lu_decompose and numx_cholesky_decompose, #51, for the established style of matrix decomposition functions in this codebase).

Follow CONTRIBUTING.md exactly: full Doxygen header, NULL-checks, numx_status_t return, all four deliverables (header, impl, test, docs page). Test against known QR examples and verify Q is orthogonal (Q^T Q = I) and QR reconstructs the original matrix, following the same reconstruction-test pattern #51 used for Cholesky (test_cholesky_decompose_residual_reconstruction in tests/test_linalg.c).

Contributor guide

Research direction
Study the existing numx lu decompose and numx cholesky decompose implementations for style and structure. Implement the Householder QR decomposition algorithm, bounded by NUMX MAX MAT ROWS and NUMX MAX MAT COLS. Write unit tests that verify Q is orthogonal (Q^T Q = I) and that QR reconstructs the original matrix. Follow CONTRIBUTING.md for deliverables.
Tech stack
c
Domain
backend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
CLinear algebra (QR decomposition)
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70