DLANSY(l) ) DLANSY(l)NAME
DLANSY - return 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
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 sym‐
metric 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 Frobenius 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 referenced. = 'U': Upper triangu‐
lar part of A is referenced
= '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.
A (input) DOUBLE PRECISION array, dimension (LDA,N)
The symmetric matrix A. If UPLO = 'U', the leading 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 referenced. If UPLO = 'L', the leading n by n lower trian‐
gular part of A contains the lower triangular part of the
matrix A, and the strictly upper triangular 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.
LAPACK version 3.0 15 June 2000 DLANSY(l)
