# slangt.f - Man Page

## Synopsis

### Functions/Subroutines

real function **slangt** (NORM, **N**, DL, D, 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.

## Function/Subroutine Documentation

### real function slangt (character NORM, integer N, 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:**December 2016

Definition at line 108 of file slangt.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

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

Tue Nov 14 2017 Version 3.8.0 LAPACK