ZHETRI - compute the inverse of a complex Hermitian indef
inite matrix A using the factorization A = U*D*U**H or A =
L*D*L**H computed by ZHETRF
SYNOPSIS
SUBROUTINE ZHETRI( UPLO, N, A, LDA, IPIV, WORK, INFO )
CHARACTER UPLO
INTEGER INFO, LDA, N
INTEGER IPIV( * )
COMPLEX*16 A( LDA, * ), WORK( * )
PURPOSE
ZHETRI computes the inverse of a complex Hermitian indefi
nite matrix A using the factorization A = U*D*U**H or A =
L*D*L**H computed by ZHETRF.
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*16 array, dimension (LDA,N)
On entry, the block diagonal matrix D and the mul
tipliers used to obtain the factor U or L as com
puted by ZHETRF.
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 struc
ture of D as determined by ZHETRF.
WORK (workspace) COMPLEX*16 array, dimension (N)
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille
gal value
> 0: if INFO = i, D(i,i) = 0; the matrix is singu
lar and its inverse could not be computed.
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