double precision function dlangt (NORM, N, DL, D, DU)
DLANGT returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value of any element of a general tridiagonal matrix.
DLANGT 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:
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 = ( 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 is CHARACTER*1
Specifies the value to be returned in DLANGT as described
above.
N
N is INTEGER
The order of the matrix A. N >= 0. When N = 0, DLANGT is
set to zero.
DL
DL is DOUBLE PRECISION array, dimension (N-1)
The (n-1) sub-diagonal elements of A.
D
D is DOUBLE PRECISION array, dimension (N)
The diagonal elements of A.
DU
DU is DOUBLE PRECISION array, dimension (N-1)
The (n-1) super-diagonal elements of A.
Author:
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
Definition at line 108 of file dlangt.f.
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