DLANGT
November 2006
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.
the infinity norm, or the element of largest absolute value of a
real tridiagonal matrix A.
Description
DLANGT returns the value
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.
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.
Arguments
| NORM |
(input) CHARACTER*1
Specifies the value to be returned in DLANGT as described
above. |
| N |
(input) INTEGER
The order of the matrix A. N >= 0. When N = 0, DLANGT is
set to zero. |
| DL |
(input) DOUBLE PRECISION array, dimension (N-1)
The (n-1) sub-diagonal elements of A.
|
| D |
(input) DOUBLE PRECISION array, dimension (N)
The diagonal elements of A.
|
| DU |
(input) DOUBLE PRECISION array, dimension (N-1)
The (n-1) super-diagonal elements of A.
|