Scippy

SCIP

Solving Constraint Integer Programs

presol_dualinfer.h
Go to the documentation of this file.
1 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
2 /* */
3 /* This file is part of the program and library */
4 /* SCIP --- Solving Constraint Integer Programs */
5 /* */
6 /* Copyright 2002-2022 Zuse Institute Berlin */
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 presol_dualinfer.h
26  * @ingroup PRESOLVERS
27  * @brief dual inference presolver
28  * @author Dieter Weninger
29  * @author Patrick Gemander
30  *
31  * This presolver does bound strengthening on continuous variables (columns) for getting bounds on dual variables y.
32  * The bounds of the dual variables are then used to fix primal variables or change the side of constraints.
33  * For ranged rows one needs to decide which side (rhs or lhs) determines the equality.
34  *
35  * We distinguish two cases concerning complementary slackness:
36  * i) reduced cost fixing: c_j - sup_y(y^T A_{.j}) > 0 => x_j = l_j
37  * c_j - inf_y(y^T A_{.j}) < 0 => x_j = u_j
38  * ii) positive dual lower bound: y_i > 0 => A_{i.}x = b_i
39  *
40  * Further information on this presolving approach are given in
41  * Achterberg et al. "Presolve reductions in mixed integer programming"
42  * and for a two-column extension in
43  * Chen et al. "Two-row and two-column mixed-integer presolve using hasing-based pairing methods".
44  */
45 
46 /*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/
47 
48 #ifndef __SCIP_PRESOL_DUALINFER_H__
49 #define __SCIP_PRESOL_DUALINFER_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 dual inference 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
type definitions for SCIP&#39;s main datastructure
SCIP_RETCODE SCIPincludePresolDualinfer(SCIP *scip)
common defines and data types used in all packages of SCIP