CouenneExprDiv.hpp

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/* $Id: CouenneExprDiv.hpp 615 2011-06-08 20:36:24Z pbelotti $
 *
 * Name:    exprDiv.hpp
 * Author:  Pietro Belotti
 * Purpose: definition of divisions
 *
 * (C) Carnegie-Mellon University, 2006-10.
 * This file is licensed under the Eclipse Public License (EPL)
 */

#ifndef COUENNE_EXPRDIV_HPP
#define COUENNE_EXPRDIV_HPP

#include "CouenneExprOp.hpp"
#include "CouennePrecisions.hpp"

namespace Couenne {

#define BR_NEXT_ZERO 1e-3
#define BR_MULT      1e-3


class exprDiv: public exprOp {

 public:

  exprDiv (expression **al, int n = 2): 
    exprOp (al, n) {} //< non-leaf expression, with argument list

  exprDiv (expression *arg0, expression *arg1):
    exprOp (arg0, arg1) {}

  expression *clone (Domain *d = NULL) const
    {return new exprDiv (clonearglist (d), nargs_);}

  std::string printOp () const
    {return "/";}

  inline CouNumber operator () ();

  CouNumber gradientNorm (const double *x);

  expression *differentiate (int index); 

  expression *simplify ();

  inline int Linearity () {

    if (arglist_ [1] -> Type () == CONST)
      return arglist_ [0] -> Linearity ();
    else return NONLINEAR;
  }

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

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

  exprAux *standardize (CouenneProblem *p, bool addAux = true);

  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_EXPRDIV;}

  bool isInteger ();

  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 void closestFeasible (expression *varind,
                                expression *vardep, 
                                CouNumber &left,
                                CouNumber &right) const;

  virtual bool isCuttable (CouenneProblem *problem, int index) const
  {return false;} // concave on both sides, as for products
};



inline CouNumber exprDiv::operator () ()
  {return ((*(*arglist_)) () / (*(arglist_ [1])) ());}


#define SAFE_COEFFICIENT 1e9


inline bool is_boundbox_regular (register CouNumber b1, register CouNumber b2) {

  // Why SAFE_COEFFICIENT and not COUENNE_INFINITY? Because
  // OsiRowCut::set[LU]b do not work for values more than
  // SAFE_COEFFICIENT and apparently makes the convexification
  // infeasible.
  return 
    (fabs (b1)    < SAFE_COEFFICIENT) && 
    (fabs (b2)    < SAFE_COEFFICIENT) && 
    (fabs (b1*b2) < SAFE_COEFFICIENT);
    //    && ((fabs (b1) > COUENNE_EPS) || (fabs (b2) > COUENNE_EPS));
}

}

#endif