Scippy

SCIP

Solving Constraint Integer Programs

heur_locks.h
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1/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
2/* */
3/* This file is part of the program and library */
4/* SCIP --- Solving Constraint Integer Programs */
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6/* Copyright (c) 2002-2024 Zuse Institute Berlin (ZIB) */
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8/* Licensed under the Apache License, Version 2.0 (the "License"); */
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23/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
24
25/**@file heur_locks.h
26 * @ingroup PRIMALHEURISTICS
27 * @brief locks primal heuristic
28 * @author Michael Winkler
29 * @author Gerald Gamrath
30 *
31 * The locks heuristic is a start heuristic that first tries to fix all binary variables, then solves the resulting LP
32 * and tries to round the solution and finally solves a sub-MIP on the remaining problem if the LP solution could not be
33 * rounded. The fixing works as follows: First, all variables are sorted by their total number of rounding locks (up-
34 * and down-locks summed up). Then, looking at the variable with the highest number of locks first, the variable is
35 * fixed to the bound where there are fewer locks (in case of ties, the bound which is better w.r.t. the objective
36 * function). This fix is propagated and the activities of all LP rows are updated. If any LP row becomes redundant
37 * w.r.t. the updated bounds, we adjust the rounding locks.
38 */
39
40/*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/
41
42#ifndef __SCIP_HEUR_LOCKS_H__
43#define __SCIP_HEUR_LOCKS_H__
44
45#include "scip/def.h"
46#include "scip/type_heur.h"
47#include "scip/type_retcode.h"
48#include "scip/type_scip.h"
49
50#ifdef __cplusplus
51extern "C" {
52#endif
53
54/** creates the locks primal heuristic and includes it in SCIP
55 *
56 * @ingroup PrimalHeuristicIncludes
57 */
58SCIP_EXPORT
60 SCIP* scip /**< SCIP data structure */
61 );
62
63
64/** apply fix-and-propagate scheme based on variable locks
65 *
66 * @note probing mode of SCIP needs to be enabled before
67 */
68SCIP_EXPORT
70 SCIP* scip, /**< SCIP data structure */
71 SCIP_HEURDATA* heurdata, /**< primal heuristic data */
72 SCIP_Bool* cutoff, /**< pointer to store if a cutoff was detected */
73 SCIP_Bool* allrowsfulfilled /**< pointer to store if all rows became redundant */
74 );
75
76#ifdef __cplusplus
77}
78#endif
79
80#endif
common defines and data types used in all packages of SCIP
#define SCIP_Bool
Definition: def.h:91
SCIP_RETCODE SCIPincludeHeurLocks(SCIP *scip)
Definition: heur_locks.c:1081
SCIP_RETCODE SCIPapplyLockFixings(SCIP *scip, SCIP_HEURDATA *heurdata, SCIP_Bool *cutoff, SCIP_Bool *allrowsfulfilled)
Definition: heur_locks.c:192
type definitions for primal heuristics
struct SCIP_HeurData SCIP_HEURDATA
Definition: type_heur.h:77
type definitions for return codes for SCIP methods
enum SCIP_Retcode SCIP_RETCODE
Definition: type_retcode.h:63
type definitions for SCIP's main datastructure