clanhs(3)

NAME

CLANHS - return the value of the one norm, or the Frobe

nius norm, or the infinity norm, or the element of largest abso

lute value of a Hessenberg matrix A

SYNOPSIS

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

PURPOSE

CLANHS 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

CLANHS returns the value

CLANHS = ( 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 ma

trix (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 CLANHS as

described above.

N (input) INTEGER

The order of the matrix A. N >= 0. When N = 0,

CLANHS is set to zero.

A (input) COMPLEX 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.

LAPACK version 3.0 15 June 2000

CLANHS(3)