Flashnux

GNU/Linux man pages

Livre :
Expressions régulières,
Syntaxe et mise en oeuvre :

ISBN : 978-2-7460-9712-4
EAN : 9782746097124
(Editions ENI)

GNU/Linux

CentOS 4.8

 i386

dgtcon(l)
DGTCON

DGTCON

NAME
SYNOPSIS
PURPOSE
ARGUMENTS

NAME

DGTCON - estimate the reciprocal of the condition number of a real tridiagonal matrix A using the LU factorization as computed by DGTTRF

SYNOPSIS

SUBROUTINE DGTCON(

NORM, N, DL, D, DU, DU2, IPIV, ANORM, RCOND, WORK, IWORK, INFO )

CHARACTER

NORM

INTEGER

INFO, N

DOUBLE

PRECISION ANORM, RCOND

INTEGER

IPIV( * ), IWORK( * )

DOUBLE

PRECISION D( * ), DL( * ), DU( * ), DU2( * ), WORK( * )

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))).

ARGUMENTS

NORM (input) CHARACTER*1

Specifies whether the 1-norm condition number or the infinity-norm condition number is required:
= ’1’ or ’O’: 1-norm;
= ’I’: Infinity-norm.

N (input) INTEGER

The order of the matrix A. N >= 0.

DL (input) DOUBLE PRECISION array, dimension (N-1)

The (n-1) multipliers that define the matrix L from the LU factorization of A as computed by DGTTRF.

D (input) DOUBLE PRECISION array, dimension (N)

The n diagonal elements of the upper triangular matrix U from the LU factorization of A.

DU (input) DOUBLE PRECISION array, dimension (N-1)

The (n-1) elements of the first superdiagonal of U.

DU2 (input) DOUBLE PRECISION array, dimension (N-2)

The (n-2) elements of the second superdiagonal of U.

IPIV (input) 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 (input) DOUBLE PRECISION

If NORM = ’1’ or ’O’, the 1-norm of the original matrix A. If NORM = ’I’, the infinity-norm of the original matrix A.

RCOND (output) 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 1-norm of inv(A) computed in this routine.

WORK (workspace) DOUBLE PRECISION array, dimension (2*N)
IWORK (workspace) INTEGER array, dimension (N)
INFO (output) INTEGER

= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value

dgtcon(l)