CHPTRI(1) LAPACK routine (version 3.2) CHPTRI(1)NAME
CHPTRI - computes the inverse of a complex Hermitian indefinite matrix
A in packed storage using the factorization A = U*D*U**H or A =
L*D*L**H computed by CHPTRF
SYNOPSIS
SUBROUTINE CHPTRI( UPLO, N, AP, IPIV, WORK, INFO )
CHARACTER UPLO
INTEGER INFO, N
INTEGER IPIV( * )
COMPLEX AP( * ), WORK( * )
PURPOSE
CHPTRI computes the inverse of a complex Hermitian indefinite matrix A
in packed storage using the factorization A = U*D*U**H or A = L*D*L**H
computed by CHPTRF.
ARGUMENTS
UPLO (input) CHARACTER*1
Specifies whether the details of the factorization are stored
as an upper or lower triangular matrix. = 'U': Upper triangu‐
lar, 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.
AP (input/output) COMPLEX array, dimension (N*(N+1)/2)
On entry, the block diagonal matrix D and the multipliers used
to obtain the factor U or L as computed by CHPTRF, stored as a
packed triangular matrix. On exit, if INFO = 0, the (Hermit‐
ian) inverse of the original matrix, stored as a packed trian‐
gular matrix. The j-th column of inv(A) is stored in the array
AP as follows: if UPLO = 'U', AP(i + (j-1)*j/2) = inv(A)(i,j)
for 1<=i<=j; if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) =
inv(A)(i,j) for j<=i<=n.
IPIV (input) INTEGER array, dimension (N)
Details of the interchanges and the block structure of D as
determined by CHPTRF.
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 routine (version 3.2) November 2008 CHPTRI(1)
