/*  hevmax.c    CCMATH mathematics library source code.
 *
 *  Copyright (C)  2000   Daniel A. Atkinson    All rights reserved.
 *  This code may be redistributed under the terms of the GNU library
 *  public license (LGPL). ( See the lgpl.license file for details.)
 * ------------------------------------------------------------------------
 */
#include <stdlib.h>
#include "complex.h"
double hevmax(Cpx *a,Cpx *u,int n)
{ Cpx *x,*p,h;
  double e,ep,s,t,te=1.e-12;
  int k,j;
  x=(Cpx *)calloc(n,sizeof(Cpx));
  x[0].re=1.; e=0.;
  do{
    for(k=0,p=a,s=t=0.; k<n ;++k){
      for(j=0,h.re=h.im=0.; j<n ;++j,++p){
        h.re+=p->re*x[j].re-p->im*x[j].im;
	h.im+=p->im*x[j].re+p->re*x[j].im;
       }
      s+=h.re*h.re+h.im*h.im;
      t+=h.re*x[k].re+h.im*x[k].im;
      u[k]=h;
     }
    ep=e; e=s/t; s=1./sqrt(s);
    for(k=0; k<n ;++k){
      u[k].re*=s; u[k].im*=s; x[k]=u[k];
     }
   } while(fabs(e-ep)>fabs(te*e));
  free(x);
  return e;
}