cgtcon-f(3)

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

 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 is COMPLEX array, dimension (N)
 The n diagonal elements of the upper triangular matrix U from
 the LU factorization of A.

 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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