DGEQLS(3)

💅 DGEQLS(3) — bestie, it’s giving “solve the least squares problem” ✨

okay so this is a LAPACK library function page from /home/abui...IN/dgeqls.f(3) — yes that path is a whole mood, don’t worry about it — and it’s literally the manual for DGEQLS, a Fortran subroutine that solves a least squares problem using a QL factorization. no cap, it’s iconic linear algebra behavior.

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🌸 NAME 🌸

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/TESTING/LIN/dgeqls.f

that’s the file path, bestie. it’s the source file for this whole situation. slay.

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🦋 SYNOPSIS 🦋

✨ Functions/Subroutines ✨

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

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🎀 Function/Subroutine Documentation 🎀

💖 subroutine DGEQLS 💖

subroutine DGEQLS (integer m, integer n, integer nrhs, double precision,
    dimension( lda, * ) a, integer lda, double precision, dimension( * )
    tau, double precision, dimension( ldb, * ) b, integer ldb, double
    precision, dimension( lwork ) work, integer lwork, integer info)

DGEQLS

🌈 Purpose 🌈

!>
!> Solve the least squares problem
!>     min || A*X - B ||
!> using the QL factorization
!>     A = Q*L
!> computed by DGEQLF.
!>

translation for the girlies: it minimizes || A*X - B || using the QL factorization A = Q*L, and that factorization comes from DGEQLF. periodt.

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💜 Parameters 💜

• M — M is INTEGER, and it’s the number of rows of the matrix A. so the vibe check is M >= 0.
• N — N is INTEGER, and it’s the number of columns of the matrix A. the constraint is M >= N >= 0, so respect the hierarchy, bestie.
• NRHS — NRHS is INTEGER, and it’s the number of columns of B. also NRHS >= 0.
• A — A is a DOUBLE PRECISION array, dimension (LDA,N). it holds the details of the QL factorization of the original matrix A as returned by DGEQLF. so it’s not just any matrix, it’s the post-DGEQLF matrix. main character energy.
• LDA — LDA is INTEGER, and it’s the leading dimension of the array A. LDA >= M, obviously.
• TAU — TAU is a DOUBLE PRECISION array, dimension (N). it holds details of the orthogonal matrix Q. yes queen, orthogonal.
• B — B is a DOUBLE PRECISION array, dimension (LDB,NRHS). on entry, it’s the m-by-nrhs right hand side matrix B. on exit, it’s the n-by-nrhs solution matrix X, stored in rows m-n+1:m. the glow-up is real.
• LDB — LDB is INTEGER, and it’s the leading dimension of the array B. LDB >= M. no exceptions.
• WORK — WORK is a DOUBLE PRECISION array, dimension (LWORK). it’s the workspace, bestie. give it room.
• LWORK — LWORK is INTEGER, and it’s 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. so like, don’t be stingy with the workspace. 💅
• INFO — INFO is INTEGER, and it’s the status report:
  • = 0: successful exit. we love a clean run.
  • < 0: if INFO = -i, the i-th argument had an illegal value. so negative INFO means somebody’s argument was not invited to the function.

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👑 Author 👑

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

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⭐ Definition at line 120 of file dgeqls.f ⭐

that’s where the source code definition lives. iconic documentation behavior.

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🌟 Author 🌟

Generated automatically by Doxygen for LAPACK from the source code. so yes, the docs wrote themselves, and honestly? they ate.

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and that’s the page, bestie. LAPACK, Version 3.12.0, from /home/abui...IN/dgeqls.f(3) — see you in the group chat 🫶✨🎀