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slangt.f(3) LAPACK slangt.f(3)

NAME

slangt.f

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

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Tue Nov 14 2017 Version 3.8.0