Merge branch 'deterministic-heuristic-scheduler' into 'master'

Removed option to set timelimit for subscips in heur_scheduler. See merge request integer/scip!3626
scipopt · Jan 11, 2025 · 5372f6f · 5372f6f
2 parents 6ad221a + c1d3ac2
commit 5372f6f
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diff --git a/CHANGELOG b/CHANGELOG
@@ -72,6 +72,8 @@ Interface changes
 
 ### Changed parameters
 
+- heuristics/scheduler/heurtimelimit removed to avoid indeterministic behavior of scheduler heuristic, uses main time limit instead
+
 ### New parameters
 
 - branching/pscost/discountfactor, branching/relpscost/discountfactor as the discount factor for ancestral pseudo costs in pscost and relpscost branching rules

diff --git a/src/scip/heur_scheduler.c b/src/scip/heur_scheduler.c
@@ -103,7 +103,6 @@
 #define LPLIMFAC                 4.0
 #define DEFAULT_INITDURINGROOT FALSE
 #define DEFAULT_MAXCALLSSAMESOL  -1   /**< number of allowed executions of the heuristic on the same incumbent solution */
-#define DEFAULT_HEURTIMELIMIT    60.0 /**< time limit for a single heuristic run */
 
 /*
  * bandit algorithm parameters
@@ -467,7 +466,6 @@ struct SCIP_HeurData
    SCIP_Bool             initduringroot;     /**< should the heuristic be executed multiple times during the root node? */
    int                   maxnconflicts;      /**< maximum number of conflicts detected by diving heur so far */
    SCIP_Bool             defaultroot;        /**< should the default priorities be used at the root node */
-   SCIP_Real             heurtimelimit;      /**< time limit for a single heuristic run */
    /* bandit algorithm parameters */
    SCIP_Real             exp3_gamma;         /**< weight between uniform (gamma ~ 1) and weight driven (gamma ~ 0) probability distribution for exp3 */
    SCIP_Real             exp3_beta;          /**< reward offset between 0 and 1 at every observation for exp3 */
@@ -635,15 +633,14 @@ void updateFixingRate(
    case SCIP_STATUS_STALLNODELIMIT:
    case SCIP_STATUS_USERINTERRUPT:
    case SCIP_STATUS_TERMINATE:
-   case SCIP_STATUS_TIMELIMIT:
    case SCIP_STATUS_NODELIMIT:
       /* increase the fixing rate (make the subproblem easier) only if no solution was found */
       if( runstats->nbestsolsfound <= 0 )
          increaseFixingRate(fx);
       break;
-      /* fall through cases to please lint */
    case SCIP_STATUS_UNKNOWN:
    case SCIP_STATUS_TOTALNODELIMIT:
+   case SCIP_STATUS_TIMELIMIT:
    case SCIP_STATUS_MEMLIMIT:
    case SCIP_STATUS_GAPLIMIT:
    case SCIP_STATUS_PRIMALLIMIT:
@@ -1193,17 +1190,18 @@ void updateHeurStatsDiving(
 static
 void updateHeurStatsLNS(
    HEUR_STATS*           runstats,           /**< run statistics */
-   NH*                   neighborhood,       /**< the selected neighborhood or NULL if diving was used */
-   SCIP_STATUS*          subscipstatus       /**< status of the sub-SCIP solve or NULL if diving was used */
+   NH*                   neighborhood,       /**< the selected neighborhood */
+   SCIP_STATUS*          subscipstatus       /**< status of the sub-SCIP solve */
    )
-{  /*lint --e{715}*/
+{
    HEUR_STATS* stats;
 
-   assert( subscipstatus != NULL );
-
-   stats = &neighborhood->stats;
+   assert(runstats != NULL);
+   assert(neighborhood != NULL);
+   assert(subscipstatus != NULL);
 
    /* update LNS specific statistics */
+   stats = &neighborhood->stats;
    stats->usednodes += runstats->usednodes;
    ++stats->statushist[getHistIndex(*subscipstatus)]; /* update the counter for the subscip status */
 
@@ -2002,10 +2000,12 @@ SCIP_RETCODE determineLimits(
 
    heurdata = SCIPheurGetData(heur);
 
-   /* set time and memory */
+   /* check whether there is enough time and memory left */
+   SCIP_CALL( SCIPgetRealParam(scip, "limits/time", &solvelimits->timelimit) );
+   if( ! SCIPisInfinity(scip, solvelimits->timelimit) )
+      solvelimits->timelimit -= SCIPgetSolvingTime(scip);
    SCIP_CALL( SCIPgetRealParam(scip, "limits/memory", &solvelimits->memorylimit) );
    SCIP_CALL( SCIPgetBoolParam(scip, "misc/avoidmemout", &avoidmemout) );
-   solvelimits->timelimit = heurdata->heurtimelimit;
 
    /* substract the memory already used by the main SCIP and the estimated memory usage of external software */
    if( ! SCIPisInfinity(scip, solvelimits->memorylimit) )
@@ -2016,13 +2016,14 @@ SCIP_RETCODE determineLimits(
 
    /* abort if no time is left or not enough memory (we don't abort in this case if misc_avoidmemout == FALSE)
    * to create a copy of SCIP, including external memory usage */
-   if( avoidmemout && solvelimits->memorylimit <= 2.0*SCIPgetMemExternEstim(scip)/1048576.0 )
+   if( solvelimits->timelimit <= 0.0 || (avoidmemout && solvelimits->memorylimit <= 2.0*SCIPgetMemExternEstim(scip)/1048576.0) )
    {
       SCIPdebugMsg(scip, "Aborting LNS heuristic call: Not enough memory or time left.\n");
       *runagain = FALSE;
       return SCIP_OKAY;
    }
 
+   /* TODO: set stalling limit */
    solvelimits->stallnodes = -1;
    solvelimits->nodelimit = (SCIP_Longint) heurdata->neighborhoods[selection]->nodelimit;
 
@@ -2035,8 +2036,7 @@ SCIP_Real getReward(
    SCIP*                 scip,               /**< SCIP data structure */
    SCIP_HEURDATA*        heurdata,           /**< heuristic data of the scheduler neighborhood */
    int                   selection,          /**< index of selected heuristic */
-   HEUR_STATS*           runstats,           /**< run statistics */
-   SCIP_STATUS           subscipstatus       /**< status of the sub-SCIP if LNS was used */
+   HEUR_STATS*           runstats            /**< run statistics */
    )
 {
    SCIP_Real totalreward;
@@ -2051,11 +2051,6 @@ SCIP_Real getReward(
    else
       effortsaved = MIN(1.0, (SCIP_Real) runstats->usednodes / (SCIP_Real)heurdata->maxlnsnodelimit);
    effortsaved = (1.0 - effortsaved);
-
-   /* if LNS heuristic terminated because of the time limit, punish it */
-   if( selection > heurdata->ndiving && subscipstatus == SCIP_STATUS_TIMELIMIT )
-      effortsaved = 0.0;
-
    assert(effortsaved >= 0.0 && effortsaved <= 1.0);
    assert(heurdata->maxlnsnodelimit > 0);
    assert(heurdata->maxdivingnodelimit > 0);
@@ -2944,7 +2939,7 @@ SCIP_DECL_HEUREXEC(heurExecScheduler)
          updateHeurStatsLNS(stats, heurdata->neighborhoods[selection - heurdata->ndiving], &subscipstatus);
 
       /* observe reward */
-      reward = getReward(scip, heurdata, selection, stats, subscipstatus);
+      reward = getReward(scip, heurdata, selection, stats);
 
       /* call was successfull if solution was found */
       if( stats->nbestsolsfound > 0 )
@@ -4467,10 +4462,6 @@ SCIP_RETCODE SCIPincludeHeurScheduler(
          "tolerance by which the fixing rate may be exceeded without generic unfixing",
          &heurdata->unfixtol, TRUE, DEFAULT_UNFIXTOL, 0.0, 1.0, NULL, NULL) );
 
-   SCIP_CALL( SCIPaddRealParam(scip, "heuristics/" HEUR_NAME "/heurtimelimit",
-         "time limit for a single heuristic run",
-         &heurdata->heurtimelimit, TRUE, DEFAULT_HEURTIMELIMIT, 0.0, SCIP_REAL_MAX, NULL, NULL) );
-
    SCIP_CALL( SCIPaddBoolParam(scip, "heuristics/" HEUR_NAME "/initduringroot",
          "should the heuristic be executed multiple times during the root node?",
          &heurdata->initduringroot, TRUE, DEFAULT_INITDURINGROOT, NULL, NULL) );