CHPCON - estimate the reciprocal of the condition number
of a complex Hermitian packed matrix A using the factor
ization A = U*D*U**H or A = L*D*L**H computed by CHPTRF
SYNOPSIS
SUBROUTINE CHPCON( UPLO, N, AP, IPIV, ANORM, RCOND, WORK,
INFO )
CHARACTER UPLO
INTEGER INFO, N
REAL ANORM, RCOND
INTEGER IPIV( * )
COMPLEX AP( * ), WORK( * )
PURPOSE
CHPCON estimates the reciprocal of the condition number of
a complex Hermitian packed matrix A using the factoriza
tion A = U*D*U**H or A = L*D*L**H computed by CHPTRF. An
estimate is obtained for norm(inv(A)), and the reciprocal
of the condition number is computed as RCOND = 1 / (ANORM
* norm(inv(A))).
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.
AP (input) COMPLEX array, dimension (N*(N+1)/2)
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.
IPIV (input) INTEGER array, dimension (N)
Details of the interchanges and the block struc
ture of D as determined by CHPTRF.
ANORM (input) REAL
The 1-norm of the original matrix A.
RCOND (output) REAL
The reciprocal of the condition number of the
matrix A, computed as RCOND = 1/(ANORM * AINVNM),
where AINVNM is an estimate of the 1-norm of
WORK (workspace) COMPLEX array, dimension (2*N)
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille
gal value
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