---
name: "ztbt06.f"
section: "3"
platform: "linux"
package: "lapack-doc"
version: "3.12.1-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/ztbt06.f"
---

# ztbt06.f(3)

## NAME

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

Univ. of Colorado Denver

NAG Ltd.

Definition at line **124** of file **ztbt06.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.