
sgtcon.f(3) LAPACK sgtcon.f(3)
NAME
sgtcon.f 
SYNOPSIS
Functions/Subroutines
subroutine sgtcon (NORM, N, DL, D, DU, DU2, IPIV, ANORM, RCOND, WORK, IWORK, INFO)
SGTCON
Function/Subroutine Documentation
subroutine sgtcon (characterNORM, integerN, real, dimension( * )DL, real, dimension( * )D,
real, dimension( * )DU, real, dimension( * )DU2, integer, dimension( * )IPIV, realANORM,
realRCOND, real, dimension( * )WORK, integer, dimension( * )IWORK, integerINFO)
SGTCON
Purpose:
SGTCON estimates the reciprocal of the condition number of a real
tridiagonal matrix A using the LU factorization as computed by
SGTTRF.
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 REAL array, dimension (N1)
The (n1) multipliers that define the matrix L from the
LU factorization of A as computed by SGTTRF.
D
D is REAL array, dimension (N)
The n diagonal elements of the upper triangular matrix U from
the LU factorization of A.
DU
DU is REAL array, dimension (N1)
The (n1) elements of the first superdiagonal of U.
DU2
DU2 is REAL 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 REAL
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 REAL
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 REAL 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 sgtcon.f.
Author
Generated automatically by Doxygen for LAPACK from the source code.
Version 3.4.2 Tue Sep 25 2012 sgtcon.f(3) 
