CPTCON (3)  Linux Manuals
NAME
cptcon.f 
SYNOPSIS
Functions/Subroutines
subroutine cptcon (N, D, E, ANORM, RCOND, RWORK, INFO)
CPTCON
Function/Subroutine Documentation
subroutine cptcon (integerN, real, dimension( * )D, complex, dimension( * )E, realANORM, realRCOND, real, dimension( * )RWORK, integerINFO)
CPTCON
Purpose:

CPTCON 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 CPTTRF. 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 REAL array, dimension (N) The n diagonal elements of the diagonal matrix D from the factorization of A, as computed by CPTTRF.
EE is COMPLEX array, dimension (N1) The (n1) offdiagonal elements of the unit bidiagonal factor U or L from the factorization of A, as computed by CPTTRF.
ANORMANORM is REAL The 1norm of the original matrix A.
RCONDRCOND is REAL 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 REAL 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 cptcon.f.
Author
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