Scippy

SCIP

Solving Constraint Integer Programs

heur_pscostdiving.c
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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) 2002-2020 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 visit scipopt.org. */
13 /* */
14 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
15 
16 /**@file heur_pscostdiving.c
17  * @ingroup DEFPLUGINS_HEUR
18  * @brief LP diving heuristic that chooses fixings w.r.t. the pseudo cost values
19  * @author Tobias Achterberg
20  */
21 
22 /*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/
23 
24 #include "scip/heuristics.h"
25 #include "scip/heur_pscostdiving.h"
26 #include "scip/pub_heur.h"
27 #include "scip/pub_message.h"
28 #include "scip/pub_misc.h"
29 #include "scip/pub_var.h"
30 #include "scip/scip_heur.h"
31 #include "scip/scip_mem.h"
32 #include "scip/scip_numerics.h"
33 #include "scip/scip_prob.h"
34 #include "scip/scip_sol.h"
35 #include "scip/scip_var.h"
36 #include <string.h>
37 
38 #define HEUR_NAME "pscostdiving"
39 #define HEUR_DESC "LP diving heuristic that chooses fixings w.r.t. the pseudo cost values"
40 #define HEUR_DISPCHAR SCIP_HEURDISPCHAR_DIVING
41 #define HEUR_PRIORITY -1002000
42 #define HEUR_FREQ 10
43 #define HEUR_FREQOFS 2
44 #define HEUR_MAXDEPTH -1
45 #define HEUR_TIMING SCIP_HEURTIMING_AFTERLPPLUNGE
46 #define HEUR_USESSUBSCIP FALSE /**< does the heuristic use a secondary SCIP instance? */
47 #define DIVESET_DIVETYPES SCIP_DIVETYPE_INTEGRALITY /**< bit mask that represents all supported dive types */
48 #define DIVESET_ISPUBLIC TRUE /**< is this dive set publicly available (ie., can be used by other primal heuristics?) */
49 
50 
51 /*
52  * Default parameter settings
53  */
54 
55 #define DEFAULT_MINRELDEPTH 0.0 /**< minimal relative depth to start diving */
56 #define DEFAULT_MAXRELDEPTH 1.0 /**< maximal relative depth to start diving */
57 #define DEFAULT_MAXLPITERQUOT 0.05 /**< maximal fraction of diving LP iterations compared to node LP iterations */
58 #define DEFAULT_MAXLPITEROFS 1000 /**< additional number of allowed LP iterations */
59 #define DEFAULT_MAXDIVEUBQUOT 0.8 /**< maximal quotient (curlowerbound - lowerbound)/(cutoffbound - lowerbound)
60  * where diving is performed (0.0: no limit) */
61 #define DEFAULT_MAXDIVEAVGQUOT 0.0 /**< maximal quotient (curlowerbound - lowerbound)/(avglowerbound - lowerbound)
62  * where diving is performed (0.0: no limit) */
63 #define DEFAULT_MAXDIVEUBQUOTNOSOL 0.1 /**< maximal UBQUOT when no solution was found yet (0.0: no limit) */
64 #define DEFAULT_MAXDIVEAVGQUOTNOSOL 0.0 /**< maximal AVGQUOT when no solution was found yet (0.0: no limit) */
65 #define DEFAULT_BACKTRACK TRUE /**< use one level of backtracking if infeasibility is encountered? */
66 #define DEFAULT_LPRESOLVEDOMCHGQUOT 0.15 /**< percentage of immediate domain changes during probing to trigger LP resolve */
67 #define DEFAULT_LPSOLVEFREQ 0 /**< LP solve frequency for diving heuristics */
68 #define DEFAULT_ONLYLPBRANCHCANDS TRUE /**< should only LP branching candidates be considered instead of the slower but
69  * more general constraint handler diving variable selection? */
70 #define DEFAULT_RANDSEED 103 /**< initial random seed */
71 
72 
73 /* locally defined heuristic data */
74 struct SCIP_HeurData
75 {
76  SCIP_SOL* sol; /**< working solution */
77 };
78 
79 /*
80  * local methods
81  */
82 
83 /*
84  * Callback methods
85  */
86 
87 /** copy method for primal heuristic plugins (called when SCIP copies plugins) */
88 static
89 SCIP_DECL_HEURCOPY(heurCopyPscostdiving)
90 { /*lint --e{715}*/
91  assert(scip != NULL);
92  assert(heur != NULL);
93  assert(strcmp(SCIPheurGetName(heur), HEUR_NAME) == 0);
94 
95  /* call inclusion method of primal heuristic */
97 
98  return SCIP_OKAY;
99 }
100 
101 /** destructor of primal heuristic to free user data (called when SCIP is exiting) */
102 static
103 SCIP_DECL_HEURFREE(heurFreePscostdiving) /*lint --e{715}*/
104 { /*lint --e{715}*/
105  SCIP_HEURDATA* heurdata;
107  assert(heur != NULL);
108  assert(strcmp(SCIPheurGetName(heur), HEUR_NAME) == 0);
109  assert(scip != NULL);
110 
111  /* free heuristic data */
112  heurdata = SCIPheurGetData(heur);
113  assert(heurdata != NULL);
114  SCIPfreeBlockMemory(scip, &heurdata);
115  SCIPheurSetData(heur, NULL);
116 
117  return SCIP_OKAY;
118 }
119 
120 
121 /** initialization method of primal heuristic (called after problem was transformed) */
122 static
123 SCIP_DECL_HEURINIT(heurInitPscostdiving) /*lint --e{715}*/
124 { /*lint --e{715}*/
125  SCIP_HEURDATA* heurdata;
127  assert(heur != NULL);
128  assert(strcmp(SCIPheurGetName(heur), HEUR_NAME) == 0);
129 
130  /* get heuristic data */
131  heurdata = SCIPheurGetData(heur);
132  assert(heurdata != NULL);
133 
134  /* create working solution */
135  SCIP_CALL( SCIPcreateSol(scip, &heurdata->sol, heur) );
136 
137  return SCIP_OKAY;
138 }
139 
140 
141 /** deinitialization method of primal heuristic (called before transformed problem is freed) */
142 static
143 SCIP_DECL_HEUREXIT(heurExitPscostdiving) /*lint --e{715}*/
144 { /*lint --e{715}*/
145  SCIP_HEURDATA* heurdata;
147  assert(heur != NULL);
148  assert(strcmp(SCIPheurGetName(heur), HEUR_NAME) == 0);
149 
150  /* get heuristic data */
151  heurdata = SCIPheurGetData(heur);
152  assert(heurdata != NULL);
153 
154  /* free working solution */
155  SCIP_CALL( SCIPfreeSol(scip, &heurdata->sol) );
156 
157  return SCIP_OKAY;
158 }
159 
160 /** execution method of primal heuristic */
161 static
162 SCIP_DECL_HEUREXEC(heurExecPscostdiving) /*lint --e{715}*/
163 { /*lint --e{715}*/
164  SCIP_HEURDATA* heurdata;
165  SCIP_DIVESET* diveset;
166 
167  heurdata = SCIPheurGetData(heur);
168  assert(heurdata != NULL);
169  assert(SCIPheurGetNDivesets(heur) > 0);
170  assert(SCIPheurGetDivesets(heur) != NULL);
171  diveset = SCIPheurGetDivesets(heur)[0];
172  assert(diveset != NULL);
173 
174  *result = SCIP_DIDNOTRUN;
175 
176  /* terminate if there are no integer variables (note that, e.g., SOS1 variables may be present) */
178  return SCIP_OKAY;
179 
180  SCIP_CALL( SCIPperformGenericDivingAlgorithm(scip, diveset, heurdata->sol, heur, result, nodeinfeasible, -1L, SCIP_DIVECONTEXT_SINGLE) );
181 
182  return SCIP_OKAY;
183 }
184 
185 
186 /** returns a score for the given candidate -- the best candidate maximizes the diving score */
187 static
188 SCIP_DECL_DIVESETGETSCORE(divesetGetScorePscostdiving)
189 {
190  SCIP_Real pscostdown;
191  SCIP_Real pscostup;
192  SCIP_Real pscostquot;
193 
194  SCIP_Bool mayrounddown;
195  SCIP_Bool mayroundup;
196 
197  mayrounddown = SCIPvarMayRoundDown(cand);
198  mayroundup = SCIPvarMayRoundUp(cand);
199 
200  /* bound fractions to not prefer variables that are nearly integral */
201  candsfrac = MAX(candsfrac, 0.1);
202  candsfrac = MIN(candsfrac, 0.9);
203 
204  pscostdown = SCIPgetVarPseudocostVal(scip, cand, 0.0 - candsfrac);
205  pscostup = SCIPgetVarPseudocostVal(scip, cand, 1.0 - candsfrac);
206 
207  /* determine the candidate direction. if the variable may be trivially rounded in one direction, take the other direction;
208  * otherwise, consider first the direction from the root solution, second the candidate fractionality, and
209  * last the direction of smaller pseudo costs
210  *
211  * to avoid performance variability caused by numerics we use random numbers to decide whether we want to roundup or
212  * round down if the values to compare are equal within tolerances.
213  */
214  assert(pscostdown >= 0.0 && pscostup >= 0.0);
215  if( mayrounddown != mayroundup )
216  *roundup = mayrounddown;
217  else if( SCIPisLT(scip, candsol, SCIPvarGetRootSol(cand) - 0.4)
218  || (SCIPisEQ(scip, candsol, SCIPvarGetRootSol(cand) - 0.4) && SCIPrandomGetInt(SCIPdivesetGetRandnumgen(diveset), 0, 1) == 0) )
219  *roundup = FALSE;
220  else if( SCIPisGT(scip, candsol, SCIPvarGetRootSol(cand) + 0.4)
221  || (SCIPisEQ(scip, candsol, SCIPvarGetRootSol(cand) + 0.4) && SCIPrandomGetInt(SCIPdivesetGetRandnumgen(diveset), 0, 1) == 0) )
222  *roundup = TRUE;
223  else if( SCIPisLT(scip, candsfrac, 0.3)
224  || (SCIPisEQ(scip, candsfrac, 0.3) && SCIPrandomGetInt(SCIPdivesetGetRandnumgen(diveset), 0, 1) == 0) )
225  *roundup = FALSE;
226  else if( SCIPisGT(scip, candsfrac, 0.7)
227  || (SCIPisEQ(scip, candsfrac, 0.7) && SCIPrandomGetInt(SCIPdivesetGetRandnumgen(diveset), 0, 1) == 0) )
228  *roundup = TRUE;
229  else if( SCIPisEQ(scip, pscostdown, pscostup) )
230  *roundup = (SCIPrandomGetInt(SCIPdivesetGetRandnumgen(diveset), 0, 1) == 0);
231  else if( pscostdown > pscostup )
232  *roundup = TRUE;
233  else
234  *roundup = FALSE;
235 
236  if( *roundup )
237  pscostquot = sqrt(candsfrac) * (1.0 + pscostdown) / (1.0 + pscostup);
238  else
239  pscostquot = sqrt(1.0 - candsfrac) * (1.0 + pscostup) / (1.0 + pscostdown);
240 
241  /* prefer decisions on binary variables */
242  if( SCIPvarIsBinary(cand) && !(SCIPvarMayRoundDown(cand) || SCIPvarMayRoundUp(cand)))
243  pscostquot *= 1000.0;
244 
245  assert(pscostquot >= 0);
246  *score = pscostquot;
247 
248  return SCIP_OKAY;
249 }
250 
251 #define divesetAvailablePscostdiving NULL
252 
253 /*
254  * heuristic specific interface methods
255  */
256 
257 /** creates the pscostdiving heuristic and includes it in SCIP */
259  SCIP* scip /**< SCIP data structure */
260  )
261 {
262  SCIP_HEURDATA* heurdata;
263  SCIP_HEUR* heur;
264 
265  /* create Pscostdiving primal heuristic data */
266  SCIP_CALL( SCIPallocBlockMemory(scip, &heurdata) );
267 
268  /* include primal heuristic */
269  SCIP_CALL( SCIPincludeHeurBasic(scip, &heur,
271  HEUR_MAXDEPTH, HEUR_TIMING, HEUR_USESSUBSCIP, heurExecPscostdiving, heurdata) );
272 
273  assert(heur != NULL);
274 
275  /* set non-NULL pointers to callback methods */
276  SCIP_CALL( SCIPsetHeurCopy(scip, heur, heurCopyPscostdiving) );
277  SCIP_CALL( SCIPsetHeurFree(scip, heur, heurFreePscostdiving) );
278  SCIP_CALL( SCIPsetHeurInit(scip, heur, heurInitPscostdiving) );
279  SCIP_CALL( SCIPsetHeurExit(scip, heur, heurExitPscostdiving) );
280 
281  /* create a diveset (this will automatically install some additional parameters for the heuristic)*/
285  DIVESET_ISPUBLIC, DIVESET_DIVETYPES, divesetGetScorePscostdiving, divesetAvailablePscostdiving) );
286 
287  return SCIP_OKAY;
288 }
289 
#define HEUR_PRIORITY
SCIP_Bool SCIPisEQ(SCIP *scip, SCIP_Real val1, SCIP_Real val2)
SCIP_RETCODE SCIPfreeSol(SCIP *scip, SCIP_SOL **sol)
Definition: scip_sol.c:977
#define DIVESET_DIVETYPES
#define divesetAvailablePscostdiving
const char * SCIPheurGetName(SCIP_HEUR *heur)
Definition: heur.c:1429
public methods for memory management
SCIP_HEURDATA * SCIPheurGetData(SCIP_HEUR *heur)
Definition: heur.c:1340
#define HEUR_MAXDEPTH
SCIP_RANDNUMGEN * SCIPdivesetGetRandnumgen(SCIP_DIVESET *diveset)
Definition: heur.c:700
#define DEFAULT_MAXDIVEUBQUOTNOSOL
#define DEFAULT_ONLYLPBRANCHCANDS
SCIP_EXPORT SCIP_Bool SCIPvarIsBinary(SCIP_VAR *var)
Definition: var.c:17192
SCIP_RETCODE SCIPperformGenericDivingAlgorithm(SCIP *scip, SCIP_DIVESET *diveset, SCIP_SOL *worksol, SCIP_HEUR *heur, SCIP_RESULT *result, SCIP_Bool nodeinfeasible, SCIP_Longint iterlim, SCIP_DIVECONTEXT divecontext)
Definition: heuristics.c:209
#define FALSE
Definition: def.h:73
#define TRUE
Definition: def.h:72
enum SCIP_Retcode SCIP_RETCODE
Definition: type_retcode.h:54
methods commonly used by primal heuristics
struct SCIP_HeurData SCIP_HEURDATA
Definition: type_heur.h:67
public methods for problem variables
#define SCIPfreeBlockMemory(scip, ptr)
Definition: scip_mem.h:95
LP diving heuristic that chooses fixings w.r.t. the pseudo cost values.
#define SCIPallocBlockMemory(scip, ptr)
Definition: scip_mem.h:78
public methods for SCIP variables
SCIP_RETCODE SCIPsetHeurInit(SCIP *scip, SCIP_HEUR *heur, SCIP_DECL_HEURINIT((*heurinit)))
Definition: scip_heur.c:185
SCIP_EXPORT SCIP_Bool SCIPvarMayRoundDown(SCIP_VAR *var)
Definition: var.c:3336
#define HEUR_USESSUBSCIP
int SCIPgetNIntVars(SCIP *scip)
Definition: scip_prob.c:2076
public methods for numerical tolerances
#define DEFAULT_LPSOLVEFREQ
SCIP_RETCODE SCIPcreateSol(SCIP *scip, SCIP_SOL **sol, SCIP_HEUR *heur)
Definition: scip_sol.c:320
SCIP_EXPORT SCIP_Real SCIPvarGetRootSol(SCIP_VAR *var)
Definition: var.c:13114
SCIP_RETCODE SCIPincludeHeurBasic(SCIP *scip, SCIP_HEUR **heur, const char *name, const char *desc, char dispchar, int priority, int freq, int freqofs, int maxdepth, SCIP_HEURTIMING timingmask, SCIP_Bool usessubscip, SCIP_DECL_HEUREXEC((*heurexec)), SCIP_HEURDATA *heurdata)
Definition: scip_heur.c:108
#define HEUR_FREQ
static SCIP_DECL_HEURFREE(heurFreePscostdiving)
#define HEUR_DESC
#define DEFAULT_MAXLPITEROFS
int SCIPheurGetNDivesets(SCIP_HEUR *heur)
Definition: heur.c:1637
#define DEFAULT_RANDSEED
SCIPInterval sqrt(const SCIPInterval &x)
#define HEUR_DISPCHAR
SCIP_SOL * sol
Definition: struct_heur.h:62
void SCIPheurSetData(SCIP_HEUR *heur, SCIP_HEURDATA *heurdata)
Definition: heur.c:1350
#define NULL
Definition: lpi_spx1.cpp:155
#define HEUR_FREQOFS
static SCIP_DECL_HEUREXIT(heurExitPscostdiving)
#define SCIP_CALL(x)
Definition: def.h:364
#define HEUR_NAME
#define DEFAULT_BACKTRACK
public methods for primal heuristic plugins and divesets
SCIP_EXPORT SCIP_Bool SCIPvarMayRoundUp(SCIP_VAR *var)
Definition: var.c:3347
public data structures and miscellaneous methods
int SCIPrandomGetInt(SCIP_RANDNUMGEN *randnumgen, int minrandval, int maxrandval)
Definition: misc.c:9945
SCIP_DIVESET ** SCIPheurGetDivesets(SCIP_HEUR *heur)
Definition: heur.c:1627
#define SCIP_Bool
Definition: def.h:70
SCIP_RETCODE SCIPincludeHeurPscostdiving(SCIP *scip)
SCIP_RETCODE SCIPsetHeurExit(SCIP *scip, SCIP_HEUR *heur, SCIP_DECL_HEUREXIT((*heurexit)))
Definition: scip_heur.c:201
#define HEUR_TIMING
static SCIP_DECL_DIVESETGETSCORE(divesetGetScorePscostdiving)
#define MAX(x, y)
Definition: tclique_def.h:83
#define DEFAULT_MAXDIVEAVGQUOT
#define DEFAULT_MAXRELDEPTH
#define DEFAULT_MAXDIVEUBQUOT
SCIP_RETCODE SCIPcreateDiveset(SCIP *scip, SCIP_DIVESET **diveset, SCIP_HEUR *heur, const char *name, SCIP_Real minreldepth, SCIP_Real maxreldepth, SCIP_Real maxlpiterquot, SCIP_Real maxdiveubquot, SCIP_Real maxdiveavgquot, SCIP_Real maxdiveubquotnosol, SCIP_Real maxdiveavgquotnosol, SCIP_Real lpresolvedomchgquot, int lpsolvefreq, int maxlpiterofs, unsigned int initialseed, SCIP_Bool backtrack, SCIP_Bool onlylpbranchcands, SCIP_Bool ispublic, SCIP_Bool specificsos1score, SCIP_DECL_DIVESETGETSCORE((*divesetgetscore)), SCIP_DECL_DIVESETAVAILABLE((*divesetavailable)))
Definition: scip_heur.c:311
#define DEFAULT_MAXDIVEAVGQUOTNOSOL
#define DEFAULT_MINRELDEPTH
public methods for solutions
SCIP_RETCODE SCIPsetHeurCopy(SCIP *scip, SCIP_HEUR *heur, SCIP_DECL_HEURCOPY((*heurcopy)))
Definition: scip_heur.c:153
public methods for message output
SCIP_Real SCIPgetVarPseudocostVal(SCIP *scip, SCIP_VAR *var, SCIP_Real solvaldelta)
Definition: scip_var.c:8747
#define SCIP_Real
Definition: def.h:163
SCIP_Bool SCIPisLT(SCIP *scip, SCIP_Real val1, SCIP_Real val2)
SCIP_Bool SCIPisGT(SCIP *scip, SCIP_Real val1, SCIP_Real val2)
int SCIPgetNBinVars(SCIP *scip)
Definition: scip_prob.c:2031
static SCIP_DECL_HEURINIT(heurInitPscostdiving)
SCIP_RETCODE SCIPsetHeurFree(SCIP *scip, SCIP_HEUR *heur, SCIP_DECL_HEURFREE((*heurfree)))
Definition: scip_heur.c:169
static SCIP_DECL_HEUREXEC(heurExecPscostdiving)
#define DIVESET_ISPUBLIC
public methods for primal heuristics
#define DEFAULT_LPRESOLVEDOMCHGQUOT
#define DEFAULT_MAXLPITERQUOT
public methods for global and local (sub)problems
static SCIP_DECL_HEURCOPY(heurCopyPscostdiving)