CGEQLS(3)

💅 CGEQLS(3) 💅

Okay bestie, manual-name check: this page is from the Library Functions Manual, and the top header path is /home/abui...IN/cgeqls.f(3) — it literally repeats twice, no cap. This is CGEQLS(3), LAPACK Version 3.12.0 business, and we’re about to make QL least-squares make sense. 🫶

🎀 NAME 🎀

• The NAME entry is just this file path: /home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/TESTING/LIN/cgeqls.f

✨ SYNOPSIS ✨

Functions/Subroutines

• subroutine CGEQLS (m, n, nrhs, a, lda, tau, b, ldb, work, lwork, info) — CGEQLS

💖 Function/Subroutine Documentation 💖

Here’s the full signature, exactly as the page gives it:

subroutine CGEQLS (integer m, integer n, integer nrhs, complex, dimension( lda, * ) a, integer lda, complex, dimension( * ) tau, complex, dimension( ldb, * ) b, integer ldb, complex, dimension( lwork ) work, integer lwork, integer info)

And yes, the subroutine is named CGEQLS.

🌸 Purpose 🌸

Solve the least squares problem

min || A*X - B ||

using the QL factorization

A = Q*L

computed by CGEQLF. That’s the whole glow-up. ✨

🦋 Parameters 🦋

M

M is INTEGER

The number of rows of the matrix A. Constraint: M >= 0. No row erasure, bestie.

N

N is INTEGER

The number of columns of the matrix A. Constraint: M >= N >= 0. Yep, that’s exactly what it says.

NRHS

NRHS is INTEGER

The number of columns of B. Constraint: NRHS >= 0. Right-hand side count, slay.

A

A is COMPLEX array, dimension (LDA,N)

Details of the QL factorization of the original matrix A as returned by CGEQLF. So it’s already been through the CGEQLF pipeline.

LDA

LDA is INTEGER

The leading dimension of the array A. Constraint: LDA >= M. Keep that leading dimension in check.

TAU

TAU is COMPLEX array, dimension (N)

Details of the orthogonal matrix Q. Q is lowkey the main character here.

B

B is COMPLEX array, dimension (LDB,NRHS)

On entry, the m-by-nrhs right hand side matrix B.

On exit, the n-by-nrhs solution matrix X, stored in rows m-n+1:m. Entry: RHS. Exit: solution, periodt.

LDB

LDB is INTEGER

The leading dimension of the array B. Constraint: LDB >= M. Same energy as LDA, but for B.

WORK

WORK is COMPLEX array, dimension (LWORK) Workspace, doing its quiet little job.

LWORK

LWORK is INTEGER

The length of the array WORK. LWORK must be at least NRHS, and should be at least NRHS*NB, where NB is the block size for this environment. Read that “should” as a real recommendation, bestie.

INFO

INFO is INTEGER

• = 0: successful exit
• < 0: if INFO = -i, the i-th argument had an illegal value

So INFO is the vibe check: zero means we ate, negative means an argument was not it.

👑 Author 👑

• Univ. of Tennessee
• Univ. of California Berkeley
• Univ. of Colorado Denver
• NAG Ltd.

Definition at line 120 of file cgeqls.f.

🫶 Author 🫶

Generated automatically by Doxygen for LAPACK from the source code. Automation ate that, fr fr.

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Sign-off tea 🫶 The footer gives you LAPACK Version 3.12.0 and /home/abui...IN/cgeqls.f(3), and there is no date printed in that footer — so that’s the whole source/version/date situation, no cap. Byeee bestie! 💅✨