cons_varbound.h

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/*                  This file is part of the program and library             */
/*         SCIP --- Solving Constraint Integer Programs                      */
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/*    Copyright (C) 2002-2020 Konrad-Zuse-Zentrum                            */
/*                            fuer Informationstechnik Berlin                */
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/*  SCIP is distributed under the terms of the ZIB Academic License.         */
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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/**@file   cons_varbound.h
 * @ingroup CONSHDLRS
 * @brief  Constraint handler for variable bound constraints \f$lhs \leq x + c y \leq rhs\f$.
 * @author Tobias Achterberg
 * @author Timo Berthold
 * @author Michael Winkler
 * @author Gerald Gamrath
 * @author Stefan Heinz
 *
 */

/*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/

#ifndef __SCIP_CONS_VARBOUND_H__
#define __SCIP_CONS_VARBOUND_H__


#include "scip/def.h"
#include "scip/type_cons.h"
#include "scip/type_lp.h"
#include "scip/type_retcode.h"
#include "scip/type_scip.h"
#include "scip/type_var.h"

#ifdef __cplusplus
extern "C" {
#endif

/** creates the handler for variable bound constraints and includes it in SCIP
 *
 * @ingroup ConshdlrIncludes
 * */
SCIP_EXPORT
SCIP_RETCODE SCIPincludeConshdlrVarbound(
   SCIP*                 scip                /**< SCIP data structure */
   );

/**@addtogroup CONSHDLRS
 *
 * @{
 *
 * @name Variable Bound Constraints
 *
 * @{
 *
 * This constraint handler handles a special type of linear constraints, namely variable bound constraints.
 * A variable bound constraint has the form
 * \f[
 *   lhs \leq x + c y \leq rhs
 * \f]
 * with coefficient \f$c \in Q\f$, \f$lhs\in Q \cup \{-\infty\}\f$, \f$rhs\in Q \cup \{\infty\}\f$,
 * and decision variables \f$x\f$ (non-binary) and \f$y\f$ (binary or integer).
 */

/** creates and captures a variable bound constraint: lhs <= x + c*y <= rhs
 *
 *  @note the constraint gets captured, hence at one point you have to release it using the method SCIPreleaseCons()
 */
SCIP_EXPORT
SCIP_RETCODE SCIPcreateConsVarbound(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_CONS**           cons,               /**< pointer to hold the created constraint */
   const char*           name,               /**< name of constraint */
   SCIP_VAR*             var,                /**< variable x that has variable bound */
   SCIP_VAR*             vbdvar,             /**< binary, integer or implicit integer bounding variable y */
   SCIP_Real             vbdcoef,            /**< coefficient c of bounding variable y */
   SCIP_Real             lhs,                /**< left hand side of variable bound inequality */
   SCIP_Real             rhs,                /**< right hand side of variable bound inequality */
   SCIP_Bool             initial,            /**< should the LP relaxation of constraint be in the initial LP?
                                              *   Usually set to TRUE. Set to FALSE for 'lazy constraints'. */
   SCIP_Bool             separate,           /**< should the constraint be separated during LP processing?
                                              *   Usually set to TRUE. */
   SCIP_Bool             enforce,            /**< should the constraint be enforced during node processing?
                                              *   TRUE for model constraints, FALSE for additional, redundant constraints. */
   SCIP_Bool             check,              /**< should the constraint be checked for feasibility?
                                              *   TRUE for model constraints, FALSE for additional, redundant constraints. */
   SCIP_Bool             propagate,          /**< should the constraint be propagated during node processing?
                                              *   Usually set to TRUE. */
   SCIP_Bool             local,              /**< is constraint only valid locally?
                                              *   Usually set to FALSE. Has to be set to TRUE, e.g., for branching constraints. */
   SCIP_Bool             modifiable,         /**< is constraint modifiable (subject to column generation)?
                                              *   Usually set to FALSE. In column generation applications, set to TRUE if pricing
                                              *   adds coefficients to this constraint. */
   SCIP_Bool             dynamic,            /**< is constraint subject to aging?
                                              *   Usually set to FALSE. Set to TRUE for own cuts which
                                              *   are separated as constraints. */
   SCIP_Bool             removable,          /**< should the relaxation be removed from the LP due to aging or cleanup?
                                              *   Usually set to FALSE. Set to TRUE for 'lazy constraints' and 'user cuts'. */
   SCIP_Bool             stickingatnode      /**< should the constraint always be kept at the node where it was added, even
                                              *   if it may be moved to a more global node?
                                              *   Usually set to FALSE. Set to TRUE to for constraints that represent node data. */
   );

/** creates and captures a varbound constraint
 *  in its most basic version, i. e., all constraint flags are set to their basic value as explained for the
 *  method SCIPcreateConsVarbound(); all flags can be set via SCIPsetConsFLAGNAME-methods in scip.h
 *
 *  @see SCIPcreateConsVarbound() for information about the basic constraint flag configuration
 *
 *  @note the constraint gets captured, hence at one point you have to release it using the method SCIPreleaseCons()
 */
SCIP_EXPORT
SCIP_RETCODE SCIPcreateConsBasicVarbound(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_CONS**           cons,               /**< pointer to hold the created constraint */
   const char*           name,               /**< name of constraint */
   SCIP_VAR*             var,                /**< variable x that has variable bound */
   SCIP_VAR*             vbdvar,             /**< binary, integer or implicit integer bounding variable y */
   SCIP_Real             vbdcoef,            /**< coefficient c of bounding variable y */
   SCIP_Real             lhs,                /**< left hand side of variable bound inequality */
   SCIP_Real             rhs                 /**< right hand side of variable bound inequality */
   );

/** gets left hand side of variable bound constraint lhs <= x + c*y <= rhs */
SCIP_EXPORT
SCIP_Real SCIPgetLhsVarbound(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_CONS*            cons                /**< constraint data */
   );

/** gets right hand side of variable bound constraint lhs <= x + c*y <= rhs */
SCIP_EXPORT
SCIP_Real SCIPgetRhsVarbound(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_CONS*            cons                /**< constraint data */
   );

/** gets bounded variable x of variable bound constraint lhs <= x + c*y <= rhs */
SCIP_EXPORT
SCIP_VAR* SCIPgetVarVarbound(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_CONS*            cons                /**< constraint data */
   );

/** gets bounding variable y of variable bound constraint lhs <= x + c*y <= rhs */
SCIP_EXPORT
SCIP_VAR* SCIPgetVbdvarVarbound(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_CONS*            cons                /**< constraint data */
   );

/** gets bound coefficient c of variable bound constraint lhs <= x + c*y <= rhs */
SCIP_EXPORT
SCIP_Real SCIPgetVbdcoefVarbound(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_CONS*            cons                /**< constraint data */
   );

/** gets the dual solution of the variable bound constraint in the current LP */
SCIP_EXPORT
SCIP_Real SCIPgetDualsolVarbound(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_CONS*            cons                /**< constraint data */
   );

/** gets the dual Farkas value of the variable bound constraint in the current infeasible LP */
SCIP_EXPORT
SCIP_Real SCIPgetDualfarkasVarbound(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_CONS*            cons                /**< constraint data */
   );

/** returns the linear relaxation of the given variable bound constraint; may return NULL if no LP row was yet created;
 *  the user must not modify the row!
 */
SCIP_EXPORT
SCIP_ROW* SCIPgetRowVarbound(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_CONS*            cons                /**< constraint data */
   );

/** cleans up (multi-)aggregations and fixings from varbound constraints */
SCIP_EXPORT
SCIP_RETCODE SCIPcleanupConssVarbound(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_Bool             onlychecked,        /**< should only checked constraints be cleaned up? */
   SCIP_Bool*            infeasible,         /**< pointer to return whether the problem was detected to be infeasible */
   int*                  naddconss,          /**< pointer to count number of added (linear) constraints */
   int*                  ndelconss,          /**< pointer to count number of deleted (varbound) constraints */
   int*                  nchgbds             /**< pointer to count number of bound changes */
   );

/** @} */

/** @} */

#ifdef __cplusplus
}
#endif

#endif