zptcon.f (3)  Linux Man Pages
NAME
zptcon.f 
SYNOPSIS
Functions/Subroutines
subroutine zptcon (N, D, E, ANORM, RCOND, RWORK, INFO)
ZPTCON
Function/Subroutine Documentation
subroutine zptcon (integerN, double precision, dimension( * )D, complex*16, dimension( * )E, double precisionANORM, double precisionRCOND, double precision, dimension( * )RWORK, integerINFO)
ZPTCON
Purpose:

ZPTCON computes the reciprocal of the condition number (in the 1norm) of a complex Hermitian positive definite tridiagonal matrix using the factorization A = L*D*L**H or A = U**H*D*U computed by ZPTTRF. Norm(inv(A)) is computed by a direct method, and the reciprocal of the condition number is computed as RCOND = 1 / (ANORM * norm(inv(A))).
Parameters:

N
N is INTEGER The order of the matrix A. N >= 0.
DD is DOUBLE PRECISION array, dimension (N) The n diagonal elements of the diagonal matrix D from the factorization of A, as computed by ZPTTRF.
EE is COMPLEX*16 array, dimension (N1) The (n1) offdiagonal elements of the unit bidiagonal factor U or L from the factorization of A, as computed by ZPTTRF.
ANORMANORM is DOUBLE PRECISION The 1norm of the original matrix A.
RCONDRCOND is DOUBLE PRECISION The reciprocal of the condition number of the matrix A, computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is the 1norm of inv(A) computed in this routine.
RWORKRWORK is DOUBLE PRECISION array, dimension (N)
INFOINFO is INTEGER = 0: successful exit < 0: if INFO = i, the ith argument had an illegal value
Author:

Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
 September 2012
Further Details:

The method used is described in Nicholas J. Higham, "Efficient Algorithms for Computing the Condition Number of a Tridiagonal Matrix", SIAM J. Sci. Stat. Comput., Vol. 7, No. 1, January 1986.
Definition at line 120 of file zptcon.f.
Author
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