CGETF2(3)

🎀 cgetf2(3) — Library Functions Manual 🎀

okay bestie, welcome to the cgetf2 page ✨ quick vibe check up top: the file this page documents is literally

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/cgetf2.f

yes that's a whole path, she's long, she's giving build directory realness 💅

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✨ NAME ✨

cgetf2 — bestie, this is the one that computes the LU factorization of a general m-by-n matrix using partial pivoting with row interchanges (the unblocked algorithm, iykyk 😌)

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🌸 SYNOPSIS 🌸

Functions/Subroutines

subroutine CGETF2 (m, n, a, lda, ipiv, info)

CGETF2 computes the LU factorization of a general m-by-n matrix using partial pivoting with row interchanges (unblocked algorithm). periodt 🫶

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🦋 Function/Subroutine Documentation 🦋

subroutine CGETF2 (integer m, integer n, complex, dimension( lda, * ) a,
    integer lda, integer, dimension( * ) ipiv, integer info)

CGETF2 computes the LU factorization of a general m-by-n matrix using partial pivoting with row interchanges (unblocked algorithm). no cap, that's the whole gig ✨

💖 Purpose 💖

!>
!> CGETF2 computes an LU factorization of a general m-by-n matrix A
!> using partial pivoting with row interchanges.
!>
!> The factorization has the form
!>    A = P * L * U
!> where P is a permutation matrix, L is lower triangular with unit
!> diagonal elements (lower trapezoidal if m > n), and U is upper
!> triangular (upper trapezoidal if m < n).
!>
!> This is the right-looking Level 2 BLAS version of the algorithm.
!>

so like: you hand her a matrix A, she hands you back P * L * U 💫 P is the permutation matrix, L is lower triangular with unit diagonal elements (and lower trapezoidal if m > n, she's flexible like that), and U is upper triangular (upper trapezoidal if m < n, versatility icon). and yeah, this is the right-looking Level 2 BLAS version of the algorithm, in case anyone asks 🔥

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✨ Parameters ✨

• M — M is INTEGER. the number of rows of the matrix A. M >= 0. (zero rows? valid. iconic.)
• N — N is INTEGER. the number of columns of the matrix A. N >= 0.
• A — A is COMPLEX array, dimension (LDA,N). on entry, the m by n matrix to be factored 😤 on exit, the factors L and U from the factorization A = P*L*U. heads up bestie: the unit diagonal elements of L are not stored — she's lowkey minimalist about it.
• LDA — LDA is INTEGER. the leading dimension of the array A. LDA >= max(1,M). respect the leading dimension or perish fr fr 💀
• IPIV — IPIV is INTEGER array, dimension (min(M,N)). the pivot indices 🎯 for 1 <= i <= min(M,N), row i of the matrix was interchanged with row IPIV(i).
• INFO — INFO is INTEGER. the receipts, ie:
  • = 0: successful exit 🎉
  • < 0: if INFO = -k, the k-th argument had an illegal value 🙈
  • > 0: if INFO = k, U(k,k) is exactly zero. the factorization has been completed, but the factor U is exactly singular, and division by zero will occur if it is used to solve a system of equations. ⚠️ like, that's a real yikes, be careful

bestie please actually check INFO and the pivot array. singular U = division by zero = your solve is gonna be a whole mess 😭

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👑 Author 👑

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

(all the legends, in that order, every single one 💜)

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🧚 Definition 🧚

Definition at line 107 of file cgetf2.f. 📍

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🌈 Author 🌈

Generated automatically by Doxygen for LAPACK from the source code. (she's a bot, a very diligent bot 🤖✨)

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LAPACK — Version 3.12.0 — /home/abui...RC/cgetf2.f(3)

and that's the page bestie!! 💅 mwah, go factor some matrices responsibly, and remember: LDA >= max(1,M) or she will simply not 😤🎀