optimization problems with standard inputs. For
            these problems, the user does not have to create the <tt>penm</tt> object, nor the call back functions. Pre-programmed interfaces can be found in directory <tt>interfaces</tt>.
         </p>
         <p><b>Nonlinear optimization with AMPL input</b></p>
         <p>Go to directory <tt>interfaces/NLP_AMPL</tt>. Assume that nonlinear optimization problem is defined in and processed by <a href="http://www.ampl.com">AMPL</a>, so that we have the corresp