# dlanst.f man page

dlanst.f —

## Synopsis

### Functions/Subroutines

DOUBLE PRECISION functiondlanst(NORM, N, D, E)DLANSTreturns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a real symmetric tridiagonal matrix.

## Function/Subroutine Documentation

### DOUBLE PRECISION function dlanst (characterNORM, integerN, double precision, dimension( * )D, double precision, dimension( * )E)

**DLANST** returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a real symmetric tridiagonal matrix.

**Purpose:**

```
DLANST returns the value of the one norm, or the Frobenius norm, or
the infinity norm, or the element of largest absolute value of a
real symmetric tridiagonal matrix A.
```

**Returns:**

DLANST

```
DLANST = ( max(abs(A(i,j))), NORM = 'M' or 'm'
(
( norm1(A), NORM = '1', 'O' or 'o'
(
( normI(A), NORM = 'I' or 'i'
(
( normF(A), NORM = 'F', 'f', 'E' or 'e'
where norm1 denotes the one norm of a matrix (maximum column sum),
normI denotes the infinity norm of a matrix (maximum row sum) and
normF denotes the Frobenius norm of a matrix (square root of sum of
squares). Note that max(abs(A(i,j))) is not a consistent matrix norm.
```

**Parameters:**

*NORM*

```
NORM is CHARACTER*1
Specifies the value to be returned in DLANST as described
above.
```

*N*

```
N is INTEGER
The order of the matrix A. N >= 0. When N = 0, DLANST is
set to zero.
```

*D*

```
D is DOUBLE PRECISION array, dimension (N)
The diagonal elements of A.
```

*E*

```
E is DOUBLE PRECISION array, dimension (N-1)
The (n-1) sub-diagonal or super-diagonal elements of A.
```

**Author:**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**

September 2012

Definition at line 101 of file dlanst.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

dlanst(3) is an alias of dlanst.f(3).