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4    	/*         SCIP --- Solving Constraint Integer Programs                      */
5    	/*                                                                           */
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24   	
25   	/**@file   presol_dualagg.h
26   	 * @ingroup PRESOLVERS
27   	 * @brief  aggregate variables by dual arguments
28   	 * @author Dieter Weninger
29   	 *
30   	 * This presolver looks for variables which could not be handled by
31   	 * duality fixing because of one up-/downlock.
32   	 * If the constraint which delivers the up-/downlock has
33   	 * a specific structure, we can aggregate the corresponding variable.
34   	 *
35   	 * In more detail (for a minimization problem and the case of only one uplock):
36   	 *
37   	 * Given a variable \f$x_i\f$ with \f$c_i \leq 0\f$ and only one up lock (originating from a constraint c),
38   	 * we are looking for a binary variable \f$x_j\f$ such that:
39   	 * 1. if \f$x_j = 0\f$, constraint c can only be fulfilled for \f$x_i = lb_i\f$, and
40   	 * 2. if \f$x_j = 1\f$, constraint c becomes redundant and \f$x_i\f$ can be dual-fixed to its upper bound \f$ub_i\f$
41   	 * (or vice versa). Then we can perform the following aggregation: \f$x_i = lb_i + x_j (ub_i - lb_i)\f$.
42   	 *
43   	 * Similar arguments apply for the case of only one down lock and \f$c_i \geq 0\f$.
44   	 */
45   	
46   	/*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/
47   	
48   	#ifndef __SCIP_PRESOL_DUALAGG_H__
49   	#define __SCIP_PRESOL_DUALAGG_H__
50   	
51   	#include "scip/def.h"
52   	#include "scip/type_retcode.h"
53   	#include "scip/type_scip.h"
54   	
55   	#ifdef __cplusplus
56   	extern "C" {
57   	#endif
58   	
59   	/** creates the dualagg presolver and includes it in SCIP
60   	 *
61   	 * @ingroup PresolverIncludes
62   	 */
63   	SCIP_EXPORT
64   	SCIP_RETCODE SCIPincludePresolDualagg(
65   	   SCIP*                 scip                /**< SCIP data structure */
66   	   );
67   	
68   	#ifdef __cplusplus
69   	}
70   	#endif
71   	
72   	#endif
73