DLANSY - return the value of the one norm, or the Frobe
nius norm, or the infinity norm, or the element of largest
absolute value of a real symmetric matrix A
SYNOPSIS
DOUBLE PRECISION FUNCTION DLANSY( NORM, UPLO, N, A, LDA,
WORK )
CHARACTER NORM, UPLO
INTEGER LDA, N
DOUBLE PRECISION A( LDA, * ), WORK( * )
PURPOSE
DLANSY 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 symmetric matrix A.
DESCRIPTION
DLANSY returns the value
DLANSY = ( 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 Frobe
nius norm of a matrix (square root of sum of squares).
Note that max(abs(A(i,j))) is not a matrix norm.
ARGUMENTS
NORM (input) CHARACTER*1
Specifies the value to be returned in DLANSY as
described above.
UPLO (input) CHARACTER*1
Specifies whether the upper or lower triangular
part of the symmetric matrix A is to be refer
enced. = 'U': Upper triangular part of A is ref
erenced
= 'L': Lower triangular part of A is referenced
N (input) INTEGER
The order of the matrix A. N >= 0. When N = 0,
DLANSY is set to zero.
The symmetric matrix A. If UPLO = 'U', the lead
ing n by n upper triangular part of A contains the
upper triangular part of the matrix A, and the
strictly lower triangular part of A is not refer
enced. If UPLO = 'L', the leading n by n lower
triangular part of A contains the lower triangular
part of the matrix A, and the strictly upper tri
angular part of A is not referenced.
LDA (input) INTEGER
The leading dimension of the array A. LDA >=
max(N,1).
WORK (workspace) DOUBLE PRECISION array, dimension
(LWORK),
where LWORK >= N when NORM = 'I' or '1' or 'O';
otherwise, WORK is not referenced.
Man(1) output converted with
man2html