SRC/chetrf_aa.f(3)

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version 3.12.1 · 7 versions
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🌸 NAME 🌸

SRC/chetrf_aa.f — bestie, this is the Library Functions Manual page for SRC/chetrf_aa.f(3), and it's all about the CHETRF_AA subroutine. 🫶

✨ SYNOPSIS ✨

Functions/Subroutines

  • subroutine chetrf_aa (uplo, n, a, lda, ipiv, work, lwork, info) — literally the CHETRF_AA subroutine, no cap.

💅 Function/Subroutine Documentation 💅

subroutine chetrf_aa

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

CHETRF_AA ✨

🎀 Purpose 🎀

Okay so CHETRF_AA computes the factorization of a complex hermitian matrix A using the Aasen's algorithm. The form of the factorization is:

A = U**H*T*U  or  A = L*T*L**H

where U (or L) is a product of permutation and unit upper (lower) triangular matrices, and T is a hermitian tridiagonal matrix.

This is the blocked version of the algorithm, calling Level 3 BLAS. Periodt. 🔥

🌈 Parameters 🌈

UPLO

UPLO is CHARACTER*1

  • = 'U': Upper triangle of A is stored;
  • = 'L': Lower triangle of A is stored.

N

N is INTEGER

The order of the matrix A. N >= 0.

A

A is COMPLEX array, dimension (LDA,N)

On entry, the hermitian matrix A. If UPLO = 'U', the leading N-by-N upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading N-by-N lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced.

On exit, the tridiagonal matrix is stored in the diagonals and the subdiagonals of A just below (or above) the diagonals, and L is stored below (or above) the subdiagonals, when UPLO is 'L' (or 'U').

LDA

LDA is INTEGER

The leading dimension of the array A. LDA >= max(1,N).

IPIV

IPIV is INTEGER array, dimension (N)

On exit, it contains the details of the interchanges, i.e., the row and column k of A were interchanged with the row and column IPIV(k).

WORK

WORK is COMPLEX array, dimension (MAX(1,LWORK))

On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

LWORK

LWORK is INTEGER

The length of WORK. LWORK >= 1, if N <= 1, and LWORK >= 2*N, otherwise. For optimum performance LWORK >= N*(1+NB), where NB is the optimal blocksize, returned by ILAENV.

If LWORK = -1, then a workspace query is assumed; the routine only calculates the optimal size of the WORK array, returns this value as the first entry of the WORK array, and no error message related to LWORK is issued by XERBLA.

INFO

INFO is INTEGER

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

🌟 Author 🌟

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

Definition at line 133 of file chetrf_aa.f.

🦋 Author 🦋

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bye bestie 🫶 this page is SRC/chetrf_aa.f(3), LAPACK Version 3.12.0, and that's literally the sign-off. 💖✨🎀

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