
dgtcon.f(3) LAPACK dgtcon.f(3)
NAME
dgtcon.f 
SYNOPSIS
Functions/Subroutines
subroutine dgtcon (NORM, N, DL, D, DU, DU2, IPIV, ANORM, RCOND, WORK, IWORK, INFO)
DGTCON
Function/Subroutine Documentation
subroutine dgtcon (characterNORM, integerN, double precision, dimension( * )DL, double
precision, dimension( * )D, double precision, dimension( * )DU, double precision,
dimension( * )DU2, integer, dimension( * )IPIV, double precisionANORM, double
precisionRCOND, double precision, dimension( * )WORK, integer, dimension( * )IWORK,
integerINFO)
DGTCON
Purpose:
DGTCON estimates the reciprocal of the condition number of a real
tridiagonal matrix A using the LU factorization as computed by
DGTTRF.
An estimate is obtained for norm(inv(A)), and the reciprocal of the
condition number is computed as RCOND = 1 / (ANORM * norm(inv(A))).
Parameters:
NORM
NORM is CHARACTER*1
Specifies whether the 1norm condition number or the
infinitynorm condition number is required:
= '1' or 'O': 1norm;
= 'I': Infinitynorm.
N
N is INTEGER
The order of the matrix A. N >= 0.
DL
DL is DOUBLE PRECISION array, dimension (N1)
The (n1) multipliers that define the matrix L from the
LU factorization of A as computed by DGTTRF.
D
D is DOUBLE PRECISION array, dimension (N)
The n diagonal elements of the upper triangular matrix U from
the LU factorization of A.
DU
DU is DOUBLE PRECISION array, dimension (N1)
The (n1) elements of the first superdiagonal of U.
DU2
DU2 is DOUBLE PRECISION array, dimension (N2)
The (n2) elements of the second superdiagonal of U.
IPIV
IPIV is INTEGER array, dimension (N)
The pivot indices; for 1 <= i <= n, row i of the matrix was
interchanged with row IPIV(i). IPIV(i) will always be either
i or i+1; IPIV(i) = i indicates a row interchange was not
required.
ANORM
ANORM is DOUBLE PRECISION
If NORM = '1' or 'O', the 1norm of the original matrix A.
If NORM = 'I', the infinitynorm of the original matrix A.
RCOND
RCOND is DOUBLE PRECISION
The reciprocal of the condition number of the matrix A,
computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is an
estimate of the 1norm of inv(A) computed in this routine.
WORK
WORK is DOUBLE PRECISION array, dimension (2*N)
IWORK
IWORK is INTEGER array, dimension (N)
INFO
INFO 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
Definition at line 146 of file dgtcon.f.
Author
Generated automatically by Doxygen for LAPACK from the source code.
Version 3.4.2 Tue Sep 25 2012 dgtcon.f(3) 
