iisfinder_greedy.h

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/**@file   iisfinder_greedy.h
 * @ingroup IISFINDERS
 * @brief  greedy deletion and addition filter heuristic to compute IISs
 * @author Marc Pfetsch
 * @author Mark Turner
 * @author Paul Meinhold
 *
 * An irreducible infeasible subsystem (IIS) is a subset of the constraints and bounds from a problem
 * that is infeasible.
 * The greedy filter heuristic has two different approaches for producing an (I)IS:
 * - Remove constraints such that the remaining problem is still infeasible.
 * - Add constraints from an empty problem until the problem becomes infeasible.
 * Both these approaches can be augmented to include bounds. That is, existing bounds can be deleted
 * while the IS remains infeasible. A common approach is to also apply the deletion based
 * filter after applying the additive based filter.
 * This greedy algorithm is based on
 *
 * O. Guieu and J. Chinneck, Analyzing infeasible mixed-integer and integer linear programs,@p
 * INFORMS J. Comput. 11, no. 1 (1999), pp. 63–77.
 *
 * If the appropriate parameters are set then we can guarantee that the result is irreducible, i.e.,
 * an irreducible infeasible subsystem (IIS). Otherwise we may only obtain an infeasible subsystem (IS).
 * This algorithm cannot guarantee to find the smallest possible IIS.
 */
 
/*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/
 
#ifndef __IISFINDER_GREEDY_H__
#define __IISFINDER_GREEDY_H__
 
#include <scip/scip.h>
 
#ifdef __cplusplus
extern "C" {
#endif
 
/** creates the greedy IIS finder rule and includes it in SCIP
 *
 * @ingroup IISfinderIncludes
 */
SCIP_EXPORT
SCIP_RETCODE SCIPincludeIISfinderGreedy(
   SCIP*                 scip                /**< SCIP data structure */
   );
 
/**@addtogroup IISFINDERS
 *
 * @{
 */
 
/** perform the greedy deletion algorithm with singleton batches to obtain an irreducible infeasible subsystem (IIS) */
SCIP_EXPORT
SCIP_RETCODE SCIPiisGreedyMakeIrreducible(
   SCIP_IIS*             iis                 /**< IIS data structure */
   );
 
/** @} */
 
#ifdef __cplusplus
}
#endif
 
#endif