docs: public void symm2x2_fast( double a11 , double a12, double a22 )
      {
  //        double p = (a11 - a22)*0.5;
  //        double r = Math.sqrt(p*p + a12*a12);
  //
  //        value0.real = a22 + a12*a12/(r-p);
  //        value1.real = a22 - a12*a12/(r+p);
  //    }
  //
  //    public void symm2x2_std( double a11 , double a12, double a22 )
  //    {
          double left  = (a11+a22)*0.5;
          double b     = (a11-a22)*0.5;
          double right = Math.sqrt(b*b+a12*a12);
          value0.real = left + right;
          value1.real = left - right;
      }