Scippy

SCIP

Solving Constraint Integer Programs

heur_actconsdiving.h
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1 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
2 /* */
3 /* This file is part of the program and library */
4 /* SCIP --- Solving Constraint Integer Programs */
5 /* */
6 /* Copyright (C) 2002-2014 Konrad-Zuse-Zentrum */
7 /* fuer Informationstechnik Berlin */
8 /* */
9 /* SCIP is distributed under the terms of the ZIB Academic License. */
10 /* */
11 /* You should have received a copy of the ZIB Academic License */
12 /* along with SCIP; see the file COPYING. If not email to scip@zib.de. */
13 /* */
14 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
15 
16 /**@file heur_actconsdiving.h
17  * @ingroup PRIMALHEURISTICS
18  * @brief LP diving heuristic that chooses fixings w.r.t. the active constraints the variable appear in
19  * @author Tobias Achterberg
20  *
21  * Diving heuristic: Iteratively fixes some fractional variable and resolves the LP-relaxation, thereby simulating a
22  * depth-first-search in the tree. Active Constraint Diving chooses a variable based on the active LP rows (equations
23  * are counted twice here). The variable score is calculated as a convex combination of the number of constraints the
24  * variable appears in, the sum of all positive coefficients and the absolute sum of all negative coefficients. The
25  * chosen variable is then rounded to the closest integer. One-level backtracking is applied: If the LP gets infeasible,
26  * the last fixings is undone, and the opposite fixing is tried. If this is infeasible, too, the procedure aborts.
27  */
28 
29 /*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/
30 
31 #ifndef __SCIP_HEUR_ACTCONSDIVING_H__
32 #define __SCIP_HEUR_ACTCONSDIVING_H__
33 
34 
35 #include "scip/scip.h"
36 
37 #ifdef __cplusplus
38 extern "C" {
39 #endif
40 
41 /** creates the actconsdiving heuristic and includes it in SCIP */
42 extern
44  SCIP* scip /**< SCIP data structure */
45  );
46 
47 #ifdef __cplusplus
48 }
49 #endif
50 
51 #endif
52