# chetri2x.f man page

chetri2x.f

## Synopsis

### Functions/Subroutines

subroutine **chetri2x** (UPLO, **N**, A, **LDA**, IPIV, WORK, NB, INFO)**CHETRI2X**

## Function/Subroutine Documentation

### subroutine chetri2x (character UPLO, integer N, complex, dimension( lda, * ) A, integer LDA, integer, dimension( * ) IPIV, complex, dimension( n+nb+1,* ) WORK, integer NB, integer INFO)

**CHETRI2X**

**Purpose:**

CHETRI2X 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.

**Parameters:**-
*UPLO*UPLO is CHARACTER*1 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**H; = 'L': Lower triangular, form is A = L*D*L**H.

*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 CHETRF. 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 CHETRF.

*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.

**Date:**December 2016

Definition at line 122 of file chetri2x.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page chetri2x(3) is an alias of chetri2x.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK