# stbt06.f - Man Page

TESTING/LIN/stbt06.f

## Synopsis

### Functions/Subroutines

subroutine stbt06 (rcond, rcondc, uplo, diag, n, kd, ab, ldab, work, rat)
STBT06

## Function/Subroutine Documentation

### subroutine stbt06 (real rcond, real rcondc, character uplo, character diag, integer n, integer kd, real, dimension( ldab, * ) ab, integer ldab, real, dimension( * ) work, real rat)

STBT06

Purpose:

``` STBT06 computes a test ratio comparing RCOND (the reciprocal
condition number of a triangular matrix A) and RCONDC, the estimate
computed by STBCON.  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 REAL
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 REAL
The estimate of the reciprocal condition number computed by
STBCON.```

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 REAL 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.```

WORK

`          WORK is REAL array, dimension (N)`

RAT

```          RAT is REAL
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 123 of file stbt06.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page stbt06(3) is an alias of stbt06.f(3).

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