# ztbt06.f - Man Page

TESTING/LIN/ztbt06.f

## Synopsis

### Functions/Subroutines

subroutine ztbt06 (rcond, rcondc, uplo, diag, n, kd, ab, ldab, rwork, rat)
ZTBT06

## Function/Subroutine Documentation

### subroutine ztbt06 (double precision rcond, double precision rcondc, character uplo, character diag, integer n, integer kd, complex*16, dimension( ldab, * ) ab, integer ldab, double precision, dimension( * ) rwork, double precision rat)

ZTBT06

Purpose:

ZTBT06 computes a test ratio comparing RCOND (the reciprocal
condition number of a triangular matrix A) and RCONDC, the estimate
computed by ZTBCON.  Information about the triangular matrix A is
used if one estimate is zero and the other is non-zero to decide if
underflow in the estimate is justified.
Parameters

RCOND

RCOND is DOUBLE PRECISION
The estimate of the reciprocal condition number obtained by
forming the explicit inverse of the matrix A and computing
RCOND = 1/( norm(A) * norm(inv(A)) ).

RCONDC

RCONDC is DOUBLE PRECISION
The estimate of the reciprocal condition number computed by
ZTBCON.

UPLO

UPLO is CHARACTER
Specifies whether the matrix A is upper or lower triangular.
= 'U':  Upper triangular
= 'L':  Lower triangular

DIAG

DIAG is CHARACTER
Specifies whether or not the matrix A is unit triangular.
= 'N':  Non-unit triangular
= 'U':  Unit triangular

N

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

KD

KD is INTEGER
The number of superdiagonals or subdiagonals of the
triangular band matrix A.  KD >= 0.

AB

AB is COMPLEX*16 array, dimension (LDAB,N)
The upper or lower triangular band matrix A, stored in the
first kd+1 rows of the array. The j-th column of A is stored
in the j-th column of the array AB as follows:
if UPLO = 'U', AB(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j;
if UPLO = 'L', AB(1+i-j,j)    = A(i,j) for j<=i<=min(n,j+kd).

LDAB

LDAB is INTEGER
The leading dimension of the array AB.  LDAB >= KD+1.

RWORK

RWORK is DOUBLE PRECISION array, dimension (N)

RAT

RAT is DOUBLE PRECISION
The test ratio.  If both RCOND and RCONDC are nonzero,
RAT = MAX( RCOND, RCONDC )/MIN( RCOND, RCONDC ) - 1.
If RAT = 0, the two estimates are exactly the same.
Author

Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Definition at line 124 of file ztbt06.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page ztbt06(3) is an alias of ztbt06.f(3).

Tue Nov 28 2023 12:08:43 Version 3.12.0 LAPACK