NAME

CHETRI - compute 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

SYNOPSIS

SUBROUTINE CHETRI(
UPLO, N, A, LDA, IPIV, WORK, INFO )

CHARACTER UPLO

INTEGER INFO, LDA, N

INTEGER IPIV( ∗ )

COMPLEX A( LDA, ∗ ), WORK( ∗ )

PURPOSE

CHETRI 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. 
 

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∗∗H;
= ’L’:  Lower triangular, form is A = L∗D∗L∗∗H.

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

A       (input/output) COMPLEX array, dimension (LDA,N)
On entry, the block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by CHETRF.
 
On exit, if INFO = 0, the (Hermitian) 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 block structure of D as determined by CHETRF.

WORK    (workspace) COMPLEX array, dimension (N)

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 version 2.0  —  08 October 1994