cgtcon.f (3) Linux Manual Page

cgtcon.f –

Synopsis

Functions/Subroutines

subroutine cgtcon (NORM, N, DL, D, DU, DU2, IPIV, ANORM, RCOND, WORK, INFO)
CGTCON

Function/Subroutine Documentation

subroutine cgtcon (characterNORM, integerN, complex, dimension( * )DL, complex, dimension( * )D, complex, dimension( * )DU, complex, dimension( * )DU2, integer, dimension( * )IPIV, realANORM, realRCOND, complex, dimension( * )WORK, integerINFO)

CGTCON

Purpose:

 CGTCON estimates the reciprocal of the condition number of a complex

 tridiagonal matrix A using the LU factorization as computed by

 CGTTRF.

 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 1-norm condition number or the

 infinity-norm condition number is required:

 = ‘1’ or ‘O’: 1-norm;

 = ‘I’: Infinity-norm.

N

 N is INTEGER

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

DL

 DL is COMPLEX array, dimension (N-1)

 The (n-1) multipliers that define the matrix L from the

 LU factorization of A as computed by CGTTRF.

D

 D is COMPLEX array, dimension (N)

 The n diagonal elements of the upper triangular matrix U from

 the LU factorization of A.

DU

 DU is COMPLEX array, dimension (N-1)

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

DU2

 DU2 is COMPLEX array, dimension (N-2)

 The (n-2) 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 1-norm of the original matrix A.

 If NORM = ‘I’, the infinity-norm 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 1-norm of inv(A) computed in this routine.

WORK

 WORK is COMPLEX array, dimension (2*N)

INFO

 INFO is INTEGER

 = 0: successful exit

 < 0: if INFO = -i, the i-th 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 141 of file cgtcon.f.

Author

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