 CLANHS(3) 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

## 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 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 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 (MAX(1,LWORK)),
where LWORK >= N when NORM = 'I'; otherwise, WORK is not referenced.