DLANGT (3)  Linux Manuals
NAME
dlangt.f 
SYNOPSIS
Functions/Subroutines
DOUBLE PRECISION function dlangt (NORM, N, DL, D, DU)
DLANGT returns the value of the 1norm, Frobenius norm, infinitynorm, or the largest absolute value of any element of a general tridiagonal matrix.
Function/Subroutine Documentation
DOUBLE PRECISION function dlangt (characterNORM, integerN, double precision, dimension( * )DL, double precision, dimension( * )D, double precision, dimension( * )DU)
DLANGT returns the value of the 1norm, Frobenius norm, infinitynorm, or the largest absolute value of any element of a general tridiagonal matrix.
Purpose:

DLANGT 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:

DLANGT
DLANGT = ( 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 DLANGT as described above.
NN is INTEGER The order of the matrix A. N >= 0. When N = 0, DLANGT is set to zero.
DLDL is DOUBLE PRECISION array, dimension (N1) The (n1) subdiagonal elements of A.
DD is DOUBLE PRECISION array, dimension (N) The diagonal elements of A.
DUDU is DOUBLE PRECISION array, dimension (N1) The (n1) superdiagonal 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 dlangt.f.
Author
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