1    	/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
2    	/*                                                                           */
3    	/*                  This file is part of the program and library             */
4    	/*         SCIP --- Solving Constraint Integer Programs                      */
5    	/*                                                                           */
6    	/*  Copyright (c) 2002-2023 Zuse Institute Berlin (ZIB)                      */
7    	/*                                                                           */
8    	/*  Licensed under the Apache License, Version 2.0 (the "License");          */
9    	/*  you may not use this file except in compliance with the License.         */
10   	/*  You may obtain a copy of the License at                                  */
11   	/*                                                                           */
12   	/*      http://www.apache.org/licenses/LICENSE-2.0                           */
13   	/*                                                                           */
14   	/*  Unless required by applicable law or agreed to in writing, software      */
15   	/*  distributed under the License is distributed on an "AS IS" BASIS,        */
16   	/*  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. */
17   	/*  See the License for the specific language governing permissions and      */
18   	/*  limitations under the License.                                           */
19   	/*                                                                           */
20   	/*  You should have received a copy of the Apache-2.0 license                */
21   	/*  along with SCIP; see the file LICENSE. If not visit scipopt.org.         */
22   	/*                                                                           */
23   	/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
24   	
25   	/**@file   cons_benders.h
26   	 * @ingroup CONSHDLRS
27   	 * @brief  constraint handler for Benders' decomposition
28   	 * @author Stephen J. Maher
29   	 */
30   	
31   	/*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/
32   	
33   	#ifndef __SCIP_CONS_BENDERS_H__
34   	#define __SCIP_CONS_BENDERS_H__
35   	
36   	
37   	#include "scip/def.h"
38   	#include "scip/type_benders.h"
39   	#include "scip/type_cons.h"
40   	#include "scip/type_result.h"
41   	#include "scip/type_retcode.h"
42   	#include "scip/type_scip.h"
43   	#include "scip/type_sol.h"
44   	
45   	#ifdef __cplusplus
46   	extern "C" {
47   	#endif
48   	
49   	/** creates the handler for Benders' decomposition and includes it in SCIP
50   	 *
51   	 * @ingroup ConshdlrIncludes
52   	 * */
53   	SCIP_EXPORT
54   	SCIP_RETCODE SCIPincludeConshdlrBenders(
55   	   SCIP*                 scip                /**< SCIP data structure */
56   	   );
57   	
58   	/**@addtogroup CONSHDLRS
59   	 *
60   	 * @{
61   	 *
62   	 * @name Benders Constraints
63   	 *
64   	 * Two constraint handlers are implemented for the generation of Benders' decomposition cuts. When included in a
65   	 * problem, the Benders' decomposition constraint handlers generate cuts during the enforcement of LP and relaxation
66   	 * solutions. Additionally, Benders' decomposition cuts can be generated when checking the feasibility of solutions with
67   	 * respect to the subproblem constraints.
68   	 *
69   	 * This constraint handler has an enforcement priority that is less than the integer constraint handler. This means that
70   	 * only integer feasible solutions from the LP solver are enforced by this constraint handler. This is the traditional
71   	 * behaviour of the branch-and-check approach to Benders' decomposition. Additionally, the check priority is set low,
72   	 * such that this expensive constraint handler is only called as a final check on primal feasible solutions.
73   	 *
74   	 * This constraint handler in the standard constraint handler that should be added when using Benders' decomposition.
75   	 * Additionally, there is a flag in SCIPincludeConshdlrBenders that permits the addition of the LP constraint handler,
76   	 * cons_benderslp. The use of both cons_benders and cons_benderslp allows the user to perform a multiphase Benders'
77   	 * decomposition algorithm.
78   	 *
79   	 * @{
80   	 */
81   	
82   	/** enforces Benders' constraints for given solution
83   	 *
84   	 *  This method is called from cons_benderslp and cons_benders. If the method is called from cons_benderslp, then the
85   	 *  solutions are not guaranteed to be integer feasible. This is because the default priority is set greater than the
86   	 *  integer constraint handler. If this method is called from cons_benders, then, because the default enforcement
87   	 *  priority is set less than that of the integer constraint handler, then it can be assumed that the solutions are
88   	 *  integer feasible.
89   	 *
90   	 *  The checkint flag indicates whether integer feasibility can be assumed. If it is not assumed, i.e. checkint ==
91   	 *  FALSE, then only the convex relaxations of the subproblems are solved. If integer feasibility is assumed, i.e.
92   	 *  checkint == TRUE, then the convex relaxations and the full CIP are solved to generate Benders' cuts and check
93   	 *  solution feasibility.
94   	 */
95   	SCIP_EXPORT
96   	SCIP_RETCODE SCIPconsBendersEnforceSolution(
97   	   SCIP*                 scip,               /**< the SCIP instance */
98   	   SCIP_SOL*             sol,                /**< the primal solution to enforce, or NULL for the current LP/pseudo sol */
99   	   SCIP_CONSHDLR*        conshdlr,           /**< the constraint handler */
100  	   SCIP_RESULT*          result,             /**< the result of the enforcement */
101  	   SCIP_BENDERSENFOTYPE  type,               /**< the type of solution being enforced */
102  	   SCIP_Bool             checkint            /**< should integrality be considered when checking the subproblems */
103  	   );
104  	
105  	/** @} */
106  	
107  	/** @} */
108  	
109  	#ifdef __cplusplus
110  	}
111  	#endif
112  	
113  	#endif
114