Scippy

SCIP

Solving Constraint Integer Programs

presol_dualagg.h
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2 /* */
3 /* This file is part of the program and library */
4 /* SCIP --- Solving Constraint Integer Programs */
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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
65  SCIP* scip /**< SCIP data structure */
66  );
67 
68 #ifdef __cplusplus
69 }
70 #endif
71 
72 #endif
enum SCIP_Retcode SCIP_RETCODE
Definition: type_retcode.h:63
type definitions for return codes for SCIP methods
SCIP_RETCODE SCIPincludePresolDualagg(SCIP *scip)
type definitions for SCIP&#39;s main datastructure
common defines and data types used in all packages of SCIP