zgtcon (l)  Linux Man Pages
zgtcon: estimates the reciprocal of the condition number of a complex tridiagonal matrix A using the LU factorization as computed by ZGTTRF
Command to display zgtcon
manual in Linux: $ man l zgtcon
NAME
ZGTCON  estimates the reciprocal of the condition number of a complex tridiagonal matrix A using the LU factorization as computed by ZGTTRF
SYNOPSIS
 SUBROUTINE ZGTCON(

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

CHARACTER
NORM

INTEGER
INFO, N

DOUBLE
PRECISION ANORM, RCOND

INTEGER
IPIV( * )

COMPLEX*16
D( * ), DL( * ), DU( * ), DU2( * ), WORK( * )
PURPOSE
ZGTCON estimates the reciprocal of the condition number of a complex
tridiagonal matrix A using the LU factorization as computed by
ZGTTRF.
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 1norm condition number or the
infinitynorm condition number is required:
= aq1aq or aqOaq: 1norm;
= aqIaq: Infinitynorm.
 N (input) INTEGER

The order of the matrix A. N >= 0.
 DL (input) COMPLEX*16 array, dimension (N1)

The (n1) multipliers that define the matrix L from the
LU factorization of A as computed by ZGTTRF.
 D (input) COMPLEX*16 array, dimension (N)

The n diagonal elements of the upper triangular matrix U from
the LU factorization of A.
 DU (input) COMPLEX*16 array, dimension (N1)

The (n1) elements of the first superdiagonal of U.
 DU2 (input) COMPLEX*16 array, dimension (N2)

The (n2) 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 = aq1aq or aqOaq, the 1norm of the original matrix A.
If NORM = aqIaq, the infinitynorm 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 1norm of inv(A) computed in this routine.
 WORK (workspace) COMPLEX*16 array, dimension (2*N)

 INFO (output) INTEGER

= 0: successful exit
< 0: if INFO = i, the ith argument had an illegal value
Pages related to zgtcon
 zgtcon (3)
 zgtrfs (l)  improves the computed solution to a system of linear equations when the coefficient matrix is tridiagonal, and provides error bounds and backward error estimates for the solution
 zgtsv (l)  solves the equation A*X = B,
 zgtsvx (l)  uses the LU factorization to compute the solution to a complex system of linear equations A * X = B, A**T * X = B, or A**H * X = B,
 zgttrf (l)  computes an LU factorization of a complex tridiagonal matrix A using elimination with partial pivoting and row interchanges
 zgttrs (l)  solves one of the systems of equations A * X = B, A**T * X = B, or A**H * X = B,
 zgtts2 (l)  solves one of the systems of equations A * X = B, A**T * X = B, or A**H * X = B,
 zgbbrd (l)  reduces a complex general mbyn band matrix A to real upper bidiagonal form B by a unitary transformation