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2    	/*                                                                           */
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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.         */
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11   	/*                                                                           */
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13   	/*                                                                           */
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19   	/*                                                                           */
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21   	/*  along with SCIP; see the file LICENSE. If not visit scipopt.org.         */
22   	/*                                                                           */
23   	/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
24   	
25   	/**@file   scip_dcmp.h
26   	 * @ingroup DecompMethods
27   	 * @brief  public methods for decompositions
28   	 * @author Gregor Hendel
29   	 */
30   	
31   	/*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/
32   	
33   	#ifndef SCIP_SCIP_DECOMP_H_
34   	#define SCIP_SCIP_DECOMP_H_
35   	
36   	#include "scip/def.h"
37   	#include "scip/type_cons.h"
38   	#include "scip/type_dcmp.h"
39   	#include "scip/type_retcode.h"
40   	#include "scip/type_scip.h"
41   	
42   	#ifdef __cplusplus
43   	extern "C" {
44   	#endif
45   	
46   	/**@addtogroup DecompMethods
47   	 *
48   	 * @{
49   	 */
50   	
51   	/** creates a decomposition */
52   	SCIP_EXPORT
53   	SCIP_RETCODE SCIPcreateDecomp(
54   	   SCIP*                 scip,               /**< SCIP data structure */
55   	   SCIP_DECOMP**         decomp,             /**< pointer to store the decomposition data structure */
56   	   int                   nblocks,            /**< the number of blocks (without the linking block) */
57   	   SCIP_Bool             original,           /**< is this a decomposition in the original (TRUE) or transformed space? */
58   	   SCIP_Bool             benderslabels       /**< should the variables be labeled for the application of Benders' decomposition */
59   	   );
60   	
61   	/** frees a decomposition */
62   	SCIP_EXPORT
63   	void SCIPfreeDecomp(
64   	   SCIP*                 scip,               /**< SCIP data structure */
65   	   SCIP_DECOMP**         decomp              /**< pointer to free the decomposition data structure */
66   	   );
67   	
68   	/** adds decomposition to SCIP */
69   	SCIP_EXPORT
70   	SCIP_RETCODE SCIPaddDecomp(
71   	   SCIP*                 scip,               /**< SCIP data structure */
72   	   SCIP_DECOMP*          decomp              /**< decomposition to add */
73   	   );
74   	
75   	/** gets available user decompositions for either the original or transformed problem */
76   	SCIP_EXPORT
77   	void SCIPgetDecomps(
78   	   SCIP*                 scip,               /**< SCIP data structure */
79   	   SCIP_DECOMP***        decomps,            /**< pointer to store decompositions array */
80   	   int*                  ndecomps,           /**< pointer to store number of decompositions */
81   	   SCIP_Bool             original            /**< should the decompositions for the original problem be returned? */
82   	   );
83   	
84   	/** returns TRUE if the constraint \p cons contains only linking variables in decomposition \p decomp */
85   	SCIP_EXPORT
86   	SCIP_RETCODE SCIPhasConsOnlyLinkVars(
87   	   SCIP*                 scip,               /**< SCIP data structure */
88   	   SCIP_DECOMP*          decomp,             /**< decomposition data structure */
89   	   SCIP_CONS*            cons,               /**< the constraint */
90   	   SCIP_Bool*            hasonlylinkvars     /**< will be set to TRUE if this constraint has only linking variables */
91   	   );
92   	
93   	/** computes constraint labels from variable labels
94   	 *
95   	 *  Existing labels for the constraints are simply overridden
96   	 *
97   	 *  The computed labels depend on the flag SCIPdecompUseBendersLabels() of the decomposition. If the flag is set
98   	 *  to FALSE, the labeling assigns
99   	 *
100  	 *  - label i, if only variables labeled i are present in the constraint (and optionally linking variables)
101  	 *  - SCIP_DECOMP_LINKCONS, if there are either only variables labeled with SCIP_DECOMP_LINKVAR present, or
102  	 *    if there are variables with more than one block label.
103  	 *
104  	 *  If the flag is set to TRUE, the assignment is the same, unless variables from 2 named blocks occur in the same
105  	 *  constraint, which is an invalid labeling for the Benders case.
106  	 */
107  	SCIP_EXPORT
108  	SCIP_RETCODE SCIPcomputeDecompConsLabels(
109  	   SCIP*                 scip,               /**< SCIP data structure */
110  	   SCIP_DECOMP*          decomp,             /**< decomposition data structure */
111  	   SCIP_CONS**           conss,              /**< array of constraints */
112  	   int                   nconss              /**< number of constraints */
113  	   );
114  	
115  	/** creates a decomposition of the variables from a labeling of the constraints
116  	 *
117  	 *  NOTE: by default, the variable labeling is based on a Dantzig-Wolfe decomposition. This means that constraints in named
118  	 *  blocks have have precedence over linking constraints. If a variable exists in constraints from
119  	 *  two or more named blocks, then this variable is marked as a linking variable.
120  	 *  If a variable occurs in exactly one named block i>=0, it is assigned label i.
121  	 *  Variables which are only in linking constraints are unlabeled. However, SCIPdecompGetVarsLabels() will
122  	 *  label them as linking variables.
123  	 *
124  	 *  If the variables should be labeled for the application of Benders' decomposition, the decomposition must be
125  	 *  flagged explicitly via SCIPdecompSetUseBendersLabels().
126  	 *  With this setting, the presence in linking constraints takes precedence over the presence in named blocks.
127  	 *  Now, a variable is considered linking if it is present in at least one linking constraint and an arbitrary
128  	 *  number of constraints from named blocks.
129  	 */
130  	SCIP_EXPORT
131  	SCIP_RETCODE SCIPcomputeDecompVarsLabels(
132  	   SCIP*                 scip,               /**< SCIP data structure */
133  	   SCIP_DECOMP*          decomp,             /**< decomposition data structure */
134  	   SCIP_CONS**           conss,              /**< array of constraints */
135  	   int                   nconss              /**< number of constraints */
136  	   );
137  	
138  	/** assigns linking constraints to blocks
139  	 *
140  	 * Each linking constraint is assigned to the most frequent block among its variables.
141  	 * Variables of other blocks are relabeled as linking variables.
142  	 * Constraints that have only linking variables are skipped.
143  	 *
144  	 * @note: In contrast to SCIPcomputeDecompConsLabels(), this method potentially relabels variables.
145  	 */
146  	SCIP_EXPORT
147  	SCIP_RETCODE SCIPassignDecompLinkConss(
148  	   SCIP*                 scip,               /**< SCIP data structure */
149  	   SCIP_DECOMP*          decomp,             /**< decomposition data structure */
150  	   SCIP_CONS**           conss,              /**< array of linking constraints that should be reassigned */
151  	   int                   nconss,             /**< number of constraints */
152  	   int*                  nskipconss          /**< pointer to store the number of constraints that were skipped, or NULL */
153  	   );
154  	
155  	/** computes decomposition statistics and store them in the decomposition object */
156  	SCIP_EXPORT
157  	SCIP_RETCODE SCIPcomputeDecompStats(
158  	   SCIP*                 scip,               /**< SCIP data structure */
159  	   SCIP_DECOMP*          decomp,             /**< decomposition data structure */
160  	   SCIP_Bool             uselimits           /**< respect user limits on potentially expensive graph statistics? */
161  	   );
162  	
163  	/** @} */
164  	
165  	#ifdef __cplusplus
166  	}
167  	#endif
168  	
169  	#endif
170