man slanhs (Fonctions bibliothèques) - return the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a Hessenberg matrix A

NAME

SLANHS - return the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a Hessenberg matrix A

SYNOPSIS

REAL FUNCTION
SLANHS( NORM, N, A, LDA, WORK )
CHARACTER NORM
INTEGER LDA, N
REAL A( LDA, * ), WORK( * )

PURPOSE

SLANHS returns the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a Hessenberg matrix A.

DESCRIPTION

SLANHS returns the value

SLANHS = ( 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 SLANHS as described above.
N (input) INTEGER
The order of the matrix A. N >= 0. When N = 0, SLANHS is set to zero.
A (input) REAL array, dimension (LDA,N)
The n by n upper Hessenberg matrix A; the part of A below the first sub-diagonal is not referenced.
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(N,1).
WORK (workspace) REAL array, dimension (LWORK),
where LWORK >= N when NORM = 'I'; otherwise, WORK is not referenced.