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");          */
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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   presol_gateextraction.h
26   	 * @ingroup PRESOLVERS
27   	 * @brief  gateextraction presolver
28   	 * @author Michael Winkler
29   	 */
30   	
31   	/* This presolver tries to extract gate-constraints meaning and-constraints and set-partitioning constraints (and could
32   	 * be expanded to find xor-constraints too). This is done by detecting linearizations or systems of inequalities which
33   	 * form an and-constraint or a set-partitioning constraint. An example:
34   	 *
35   	 * we have a logicor constraint of the form:                x + y + z >= 1
36   	 *
37   	 * and we also have the following set-packing constraints: (x + y <= 1 and x + z <= 1) <=> (~x + ~y >= 1 and ~x + ~z >= 1)
38   	 *
39   	 * - these three constraints form an and-constraint:        x = ~y * ~z (x = AND(~y,~z))
40   	 *
41   	 * if an additional set-packing constraint exists:          y + z <= 1
42   	 *
43   	 * - these four constraints form a set-partitioning cons.:  x + y + z = 1
44   	 *
45   	 * some information can be found:
46   	 *
47   	 *  http://www.cs.ubc.ca/~hutter/earg/papers07/cnf-structure.pdf
48   	 *  http://www.cadence.com/cn/cadence/cadence_labs/Documents/niklas_SAT_2005_Effective.pdf
49   	 *
50   	 * We also do some check for logicor and set-packing/-partitioning constraint with the same variables to upgrade these
51   	 * both constraints into one. For example:
52   	 *
53   	 *  x + y + z >= 1 and x + y + z <= 1 form x + y + z = 1
54   	 *
55   	 */
56   	
57   	
58   	/*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/
59   	
60   	#ifndef __SCIP_PRESOL_GATEEXTRACTION_H__
61   	#define __SCIP_PRESOL_GATEEXTRACTION_H__
62   	
63   	#include "scip/def.h"
64   	#include "scip/type_retcode.h"
65   	#include "scip/type_scip.h"
66   	
67   	#ifdef __cplusplus
68   	extern "C" {
69   	#endif
70   	
71   	/** creates the gateextraction presolver and includes it in SCIP
72   	 *
73   	 * @ingroup PresolverIncludes
74   	 */
75   	SCIP_EXPORT
76   	SCIP_RETCODE SCIPincludePresolGateextraction(
77   	   SCIP*                 scip                /**< SCIP data structure */
78   	   );
79   	
80   	#ifdef __cplusplus
81   	}
82   	#endif
83   	
84   	#endif
85