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 zgbcon.f(3) LAPACK zgbcon.f(3)

zgbcon.f -

# SYNOPSIS

## Functions/Subroutines

subroutine zgbcon (NORM, N, KL, KU, AB, LDAB, IPIV, ANORM, RCOND, WORK, RWORK, INFO)

ZGBCON

# Function/Subroutine Documentation

## subroutine zgbcon (characterNORM, integerN, integerKL, integerKU, complex*16, dimension( ldab, * )AB, integerLDAB, integer, dimension( * )IPIV, double precisionANORM, double precisionRCOND, complex*16, dimension( * )WORK, double precision, dimension( * )RWORK, integerINFO)

ZGBCON
Purpose:
``` ZGBCON estimates the reciprocal of the condition number of a complex
general band matrix A, in either the 1-norm or the infinity-norm,
using the LU factorization computed by ZGBTRF.

An estimate is obtained for norm(inv(A)), and the reciprocal of the
condition number is computed as
RCOND = 1 / ( norm(A) * 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.
```
KL
```          KL is INTEGER
The number of subdiagonals within the band of A.  KL >= 0.
```
KU
```          KU is INTEGER
The number of superdiagonals within the band of A.  KU >= 0.
```
AB
```          AB is COMPLEX*16 array, dimension (LDAB,N)
Details of the LU factorization of the band matrix A, as
computed by ZGBTRF.  U is stored as an upper triangular band
matrix with KL+KU superdiagonals in rows 1 to KL+KU+1, and
the multipliers used during the factorization are stored in
rows KL+KU+2 to 2*KL+KU+1.
```
LDAB
```          LDAB is INTEGER
The leading dimension of the array AB.  LDAB >= 2*KL+KU+1.
```
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).
```
ANORM
```          ANORM is 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
```          RCOND is DOUBLE PRECISION
The reciprocal of the condition number of the matrix A,
computed as RCOND = 1/(norm(A) * norm(inv(A))).
```
WORK
```          WORK is COMPLEX*16 array, dimension (2*N)
```
RWORK
```          RWORK is DOUBLE PRECISION array, dimension (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
NAG Ltd.
Date:
November 2011
Definition at line 147 of file zgbcon.f.

# Author

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