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NAME
     zlanhs - return the value of the one norm, or the  Frobenius
     norm,  or the infinity norm, or the element of largest abso-
     lute value of a Hessenberg matrix A

SYNOPSIS
     DOUBLE PRECISION FUNCTION ZLANHS( NORM, N, A, LDA, WORK )

     CHARACTER NORM

     INTEGER LDA, N

     DOUBLE PRECISION WORK( * )

     COMPLEX*16 A( LDA, * )



     #include <sunperf.h>

     double zlanhs(char norm, int n, doublecomplex *za, int lda);

PURPOSE
     ZLANHS  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
     ZLANHS returns the value

        ZLANHS = ( 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  ZLANHS  as
               described above.

     N         (input) INTEGER
               The order of the matrix A.  N >= 0.  When N  =  0,
               ZLANHS is set to zero.

     A         (input) COMPLEX*16 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)  DOUBLE  PRECISION  array,   dimension
               (LWORK),
               where LWORK >= N when NORM = 'I'; otherwise,  WORK
               is not referenced.

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