CouenneExprInv.hpp

Go to the documentation of this file.

/* $Id: CouenneExprInv.hpp 615 2011-06-08 20:36:24Z pbelotti $
 *
 * Name:    exprInv.hpp
 * Author:  Pietro Belotti
 * Purpose: definition of inverse of a function (1/f(x))
 *
 * (C) Carnegie-Mellon University, 2006-10.
 * This file is licensed under the Eclipse Public License (EPL)
 */

#ifndef COUENNE_EXPRINV_H
#define COUENNE_EXPRINV_H

#include "CouenneExprUnary.hpp"

namespace Couenne {

inline CouNumber inv (register CouNumber arg) 
{return 1. / arg;}


inline CouNumber oppInvSqr (register CouNumber x) 
{return (- inv (x*x));}


inline CouNumber inv_dblprime (register CouNumber x) 
{return (2 * inv (x*x*x));}



class exprInv: public exprUnary {

 public:

  exprInv (expression *al): 
    exprUnary (al) {} //< non-leaf expression, with argument list

  expression *clone (Domain *d = NULL) const
    {return new exprInv (argument_ -> clone (d));}

  inline unary_function F () {return inv;}

  virtual void print (std::ostream &out = std::cout, bool = false) const;

  CouNumber gradientNorm (const double *x);

  expression *differentiate (int index); 

  virtual inline int Linearity () {
    if (argument_ -> Type () == CONST) return CONSTANT;
    else                               return NONLINEAR;
  }

  void getBounds (expression *&, expression *&);

  void getBounds (CouNumber &lb, CouNumber &ub);

  void generateCuts (expression *w, //const OsiSolverInterface &si, 
                     OsiCuts &cs, const CouenneCutGenerator *cg, 
                     t_chg_bounds * = NULL, int = -1, 
                     CouNumber = -COUENNE_INFINITY, 
                     CouNumber =  COUENNE_INFINITY);

  virtual enum expr_type code () {return COU_EXPRINV;}

  bool impliedBound (int, CouNumber *, CouNumber *, t_chg_bounds *, enum auxSign = expression::AUX_EQ);

  virtual CouNumber selectBranch (const CouenneObject *obj, 
                                  const OsiBranchingInformation *info,
                                  expression * &var, 
                                  double * &brpts, 
                                  double * &brDist, // distance of current LP
                                                    // point to new convexifications
                                  int &way);

  virtual bool isBijective() const {return true;}

  virtual CouNumber inverse(expression *vardep) const
  {
    return 1./((*vardep)());
  }

  virtual bool isCuttable (CouenneProblem *problem, int index) const;
};

}

#endif