SRC/csytri2x.f(3)

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🌸 NAME 🌸

SRC/csytri2x.f — hey bestie 💖 welcome to the SRC/csytri2x.f(3) page from the Library Functions Manual ✨

🎀 SYNOPSIS 🎀

Functions/Subroutines

subroutine csytri2x (uplo, n, a, lda, ipiv, work, nb, info)
    CSYTRI2X

💅 Function/Subroutine Documentation 💅

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subroutine csytri2x (character uplo, integer n, complex, dimension( lda, * )
a, integer lda, integer, dimension( * ) ipiv, complex, dimension(
n+nb+1,* ) work, integer nb, integer info)

CSYTRI2X

💖 Purpose 💖

CSYTRI2X computes the inverse of a real symmetric indefinite matrix A using the factorization A = U*D*U**T or A = L*D*L**T computed by CSYTRF.

✨ Parameters ✨

UPLO

UPLO is CHARACTER*1. It specifies whether the details of the factorization are stored as an upper or lower triangular matrix.

  • = 'U': Upper triangular, form is A = U*D*U**T;
  • = 'L': Lower triangular, form is A = L*D*L**T.

N

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

A

A is COMPLEX array, dimension (LDA,N).

On entry, the NNB diagonal matrix D and the multipliers used to obtain the factor U or L as computed by CSYTRF.

On exit, if INFO = 0, the (symmetric) inverse of the original matrix. 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. LDA >= max(1,N).

IPIV

IPIV is INTEGER array, dimension (N). Details of the interchanges and the NNB structure of D as determined by CSYTRF.

WORK

WORK is COMPLEX array, dimension (N+NB+1,NB+3).

NB

NB is INTEGER. Block size.

INFO

INFO is INTEGER.

  • = 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.

🌸 Author 🌸

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

📌 Definition at line 119 of file csytri2x.f.

✨ Author ✨

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