Provided by: liblapack-doc_3.3.1-1_all

#### NAME

LAPACK-3  -  computes  the  inverse  of  a COMPLEX hermitian indefinite matrix A using the
factorization A = U*D*U**T or A = L*D*L**T computed by CHETRF

#### SYNOPSIS

SUBROUTINE CHETRI2( UPLO, N, A, LDA, IPIV, WORK, LWORK, INFO )

CHARACTER       UPLO

INTEGER         INFO, LDA, LWORK, N

INTEGER         IPIV( * )

COMPLEX         A( LDA, * ), WORK( * )

#### PURPOSE

CHETRI2 computes the inverse  of  a  COMPLEX  hermitian  indefinite  matrix  A  using  the
factorization  A  =  U*D*U**T  or A = L*D*L**T computed by CHETRF. CHETRI2 set the LEADING
DIMENSION of the workspace
before calling CHETRI2X that actually computes the inverse.

#### ARGUMENTS

UPLO    (input) 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**T;
= 'L':  Lower triangular, form is A = L*D*L**T.

N       (input) INTEGER
The order of the matrix A.  N >= 0.

A       (input/output) COMPLEX array, dimension (LDA,N)
On entry, the NB 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     (input) INTEGER
The leading dimension of the array A.  LDA >= max(1,N).

IPIV    (input) INTEGER array, dimension (N)
Details of the interchanges and the NB structure of D
as determined by CHETRF.

WORK    (workspace) COMPLEX array, dimension (N+NB+1)*(NB+3)

LWORK   (input) INTEGER
The dimension of the array WORK.
WORK is size >= (N+NB+1)*(NB+3)
If LDWORK = -1, then a workspace query is assumed; the routine
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 LDWORK is issued by XERBLA.

INFO    (output) 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.

LAPACK routine (version 3.3.1)             April 2011                           CHETRI2(3lapack)