# slangt.f man page

slangt.f —

## Synopsis

### Functions/Subroutines

REAL functionslangt(NORM, N, DL, D, DU)SLANGTreturns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value of any element of a general tridiagonal matrix.

## Function/Subroutine Documentation

### REAL function slangt (characterNORM, integerN, real, dimension( * )DL, real, dimension( * )D, real, dimension( * )DU)

**SLANGT** returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value of any element of a general tridiagonal matrix.

**Purpose:**

```
SLANGT 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 tridiagonal matrix A.
```

**Returns:**

SLANGT

```
SLANGT = ( 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 SLANGT as described
above.
```

*N*

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

*DL*

```
DL is REAL array, dimension (N-1)
The (n-1) sub-diagonal elements of A.
```

*D*

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

*DU*

```
DU is REAL array, dimension (N-1)
The (n-1) 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 107 of file slangt.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

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