SRC/dlangt.f(3) | Library Functions Manual | SRC/dlangt.f(3) |
NAME
SRC/dlangt.f
SYNOPSIS
Functions/Subroutines
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.
Function/Subroutine Documentation
double precision function dlangt (character norm, integer n, double precision, dimension( * ) dl, double precision, dimension( * ) d, double precision, dimension( * ) 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.
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.
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 Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Definition at line 105 of file dlangt.f.
Author
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