SRC/chetri_rook.f(3)

💖 NAME 💖

okay so welcome to the Library Functions Manual, bestie ✨ this page is all about SRC/chetri_rook.f — yes, the whole file, that's the name, we're not being cryptic today 💅

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🎀 SYNOPSIS 🎀

Functions/Subroutines

• subroutine chetri_rook (uplo, n, a, lda, ipiv, work, info) — CHETRI_ROOK computes the inverse of HE matrix using the factorization obtained with the bounded Bunch-Kaufman (rook")diagonalpivotingmethod. 🌀

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🦋 Function/Subroutine Documentation 🦋

Here's the whole signature, character for character, no cap:

subroutine chetri_rook (character uplo, integer n, complex, dimension( lda,
* ) a, integer lda, integer, dimension( * ) ipiv, complex, dimension( *
) work, integer info)

CHETRI_ROOK computes the inverse of HE matrix using the factorization obtained with the bounded Bunch-Kaufman ("rook") diagonal pivoting method. iconic behavior honestly 🌈

✨ Purpose ✨

CHETRI_ROOK computes the inverse of a complex Hermitian indefinite matrix A using the factorization A = U*D*U**H or A = L*D*L**H computed by CHETRF_ROOK. 🔥

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🌸 Parameters 🌸

🌷 UPLO

UPLO is CHARACTER*1 — it tells you whether the details of the factorization are stored as an upper or lower triangular matrix, and honestly it's giving main character energy because it decides everything downstream:

• = 'U': Upper triangular, form is A = U*D*U**H
• = 'L': Lower triangular, form is A = L*D*L**H

🍓 N

N is INTEGER — the order of the matrix A. Constraint check: N >= 0 💅

🧚 A

A is COMPLEX array, dimension (LDA,N) — the busy one, she does two jobs:

• On entry: the block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by CHETRF_ROOK.
• On exit, if INFO = 0: the (Hermitian) inverse of the original matrix. And listen, it's tidy about it: if UPLO = 'U', the upper triangular part of the inverse is formed and the part of A below the diagonal is not referenced; if UPLO = 'L' the lower triangular part of the inverse is formed and the part of A above the diagonal is not referenced. 🙈

🦋 LDA

LDA is INTEGER — the leading dimension of the array A. Constraint: LDA >= max(1,N) ✨

💜 IPIV

IPIV is INTEGER array, dimension (N) — details of the interchanges and the block structure of D as determined by CHETRF_ROOK. she's the receipts 🧾

⭐ WORK

WORK is COMPLEX array, dimension (N) — that's it, that's the whole vibe 🌸

👑

wait, sorry, wrong heading 💀

👑 INFO

INFO is INTEGER — the vibe check at the end:

• = 0: successful exit 🎉
• < 0: if INFO = -i, the i-th argument had an illegal value 😭
• > 0: if INFO = i, D(i,i) = 0; the matrix is singular and its inverse could not be computed 💀

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🌈 Author 🌈

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

🫶 Contributors 🫶

• November 2013, Igor Kozachenko, Computer Science Division, University of California, Berkeley
• September 2007, Sven Hammarling, Nicholas J. Higham, Craig Lucas, School of Mathematics, University of Manchester

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Definition at line 127 of file chetri_rook.f. 📍

🎀 Author 🎀

Generated automatically by Doxygen for LAPACK from the source code. (yes, the robots wrote this one, we stan a self-documenting queen 🤖💖)

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LAPACK, Version 3.12.0 — and that's the whole page SRC/chetri_rook.f(3), mwah, go invert something symmetric bestie 💅💖✨