concsolver_scip.c

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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
/*                                                                           */
/*                  This file is part of the program and library             */
/*         SCIP --- Solving Constraint Integer Programs                      */
/*                                                                           */
/*  Copyright (c) 2002-2026 Zuse Institute Berlin (ZIB)                      */
/*                                                                           */
/*  Licensed under the Apache License, Version 2.0 (the "License");          */
/*  you may not use this file except in compliance with the License.         */
/*  You may obtain a copy of the License at                                  */
/*                                                                           */
/*      http://www.apache.org/licenses/LICENSE-2.0                           */
/*                                                                           */
/*  Unless required by applicable law or agreed to in writing, software      */
/*  distributed under the License is distributed on an "AS IS" BASIS,        */
/*  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. */
/*  See the License for the specific language governing permissions and      */
/*  limitations under the License.                                           */
/*                                                                           */
/*  You should have received a copy of the Apache-2.0 license                */
/*  along with SCIP; see the file LICENSE. If not visit scipopt.org.         */
/*                                                                           */
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
/**@file   concsolver_scip.c
 * @ingroup PARALLEL
 * @brief  implementation of concurrent solver interface for SCIP
 * @author Leona Gottwald
 * @author Marc Pfetsch
 */
 
/* activate the define below for a feasibility check of the solutions transferred to the main SCIP. */
/* #define SCIP_CHECK_MAINSCIP_SOLUTION */
 
/*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/
 
#include "blockmemshell/memory.h"
#include "scip/boundstore.h"
#include "scip/concsolver.h"
#include "scip/concsolver_scip.h"
#include "scip/concurrent.h"
#include "scip/pub_disp.h"
#include "scip/pub_event.h"
#include "scip/pub_heur.h"
#include "scip/pub_message.h"
#include "scip/pub_misc.h"
#include "scip/pub_paramset.h"
#include "scip/pub_sol.h"
#include "scip/pub_var.h"
#include "scip/scip_concurrent.h"
#include "scip/scip_copy.h"
#include "scip/scip_event.h"
#include "scip/scip_general.h"
#include "scip/scip_heur.h"
#include "scip/scip_mem.h"
#include "scip/scip_message.h"
#include "scip/scip_numerics.h"
#include "scip/scip_param.h"
#include "scip/scip_prob.h"
#include "scip/scip_sol.h"
#include "scip/scip_solve.h"
#include "scip/scip_solvingstats.h"
#include "scip/scip_timing.h"
#include "scip/syncstore.h"
#include "scip/prop_symmetry.h"
 
/* event handler for synchronization */
#define EVENTHDLR_NAME         "sync"
#define EVENTHDLR_DESC         "event handler for synchronization of concurrent scip solvers"
 
/*
 * Data structures
 */
 
/** event handler data */
struct SCIP_EventhdlrData
{
   int             filterpos;
};
 
/*
 * Callback methods of event handler
 */
 
/** destructor of event handler to free user data (called when SCIP is exiting) */
static
SCIP_DECL_EVENTFREE(eventFreeSync)
{  /*lint --e{715}*/
   SCIP_EVENTHDLRDATA* eventhdlrdata;
 
   assert(scip != NULL);
   assert(eventhdlr != NULL);
 
   SCIP_STRINGEQ( SCIPeventhdlrGetName(eventhdlr), EVENTHDLR_NAME, SCIP_INVALIDCALL );
 
   eventhdlrdata = SCIPeventhdlrGetData(eventhdlr);
   assert(eventhdlrdata != NULL);
 
   SCIPfreeBlockMemory(scip, &eventhdlrdata);
 
   SCIPeventhdlrSetData(eventhdlr, NULL);
 
   return SCIP_OKAY;
}
 
/** initialization method of event handler (called after problem was transformed) */
static
SCIP_DECL_EVENTINIT(eventInitSync)
{  /*lint --e{715}*/
   SCIP_EVENTHDLRDATA* eventhdlrdata;
   SCIP_SYNCSTORE*  syncstore;
 
   assert(scip != NULL);
   assert(eventhdlr != NULL);
 
   SCIP_STRINGEQ( SCIPeventhdlrGetName(eventhdlr), EVENTHDLR_NAME, SCIP_INVALIDCALL );
 
   eventhdlrdata = SCIPeventhdlrGetData(eventhdlr);
   assert(eventhdlrdata != NULL);
 
   syncstore = SCIPgetSyncstore(scip);
   assert(syncstore != NULL);
 
   if( eventhdlrdata->filterpos < 0 && SCIPsyncstoreIsInitialized(syncstore) )
   {
      /* notify SCIP that your event handler wants to react on synchronization events */
      SCIP_CALL( SCIPcatchEvent(scip, SCIP_EVENTTYPE_SYNC, eventhdlr, NULL, &eventhdlrdata->filterpos) );
   }
 
   return SCIP_OKAY;
}
 
/** deinitialization method of event handler (called before transformed problem is freed) */
static
SCIP_DECL_EVENTEXIT(eventExitSync)
{  /*lint --e{715}*/
   SCIP_EVENTHDLRDATA* eventhdlrdata;
 
   assert(scip != NULL);
   assert(eventhdlr != NULL);
 
   SCIP_STRINGEQ( SCIPeventhdlrGetName(eventhdlr), EVENTHDLR_NAME, SCIP_INVALIDCALL );
 
   eventhdlrdata = SCIPeventhdlrGetData(eventhdlr);
   assert(eventhdlrdata != NULL);
 
   /* notify SCIP that your event handler wants to drop the event type synchronization found */
   if( eventhdlrdata->filterpos >= 0 )
   {
      SCIP_CALL( SCIPdropEvent(scip, SCIP_EVENTTYPE_SYNC, eventhdlr, NULL, eventhdlrdata->filterpos) );
      eventhdlrdata->filterpos = -1;
   }
 
   return SCIP_OKAY;
}
 
/** execution method of event handler */
static
SCIP_DECL_EVENTEXEC(eventExecSync)
{  /*lint --e{715}*/
   assert(eventhdlr != NULL);
   assert(event != NULL);
   assert(scip != NULL);
 
   SCIP_STRINGEQ( SCIPeventhdlrGetName(eventhdlr), EVENTHDLR_NAME, SCIP_INVALIDCALL );
 
   SCIP_CALL( SCIPsynchronize(scip) );
 
   return SCIP_OKAY;
}
 
 
/** includes event handler for synchronization found */
static
SCIP_RETCODE includeEventHdlrSync(
   SCIP*                 scip                /**< SCIP data structure */
   )
{
   SCIP_EVENTHDLR*     eventhdlr;
   SCIP_EVENTHDLRDATA* eventhdlrdata;
 
   SCIP_CALL( SCIPallocBlockMemory(scip, &eventhdlrdata) );
   eventhdlrdata->filterpos = -1;
 
   /* create event handler for events on watched variables */
   SCIP_CALL( SCIPincludeEventhdlrBasic(scip, &eventhdlr, EVENTHDLR_NAME, EVENTHDLR_DESC, eventExecSync, eventhdlrdata) );
   assert(eventhdlr != NULL);
 
   SCIP_CALL( SCIPsetEventhdlrFree(scip, eventhdlr, eventFreeSync) );
   SCIP_CALL( SCIPsetEventhdlrInit(scip, eventhdlr, eventInitSync) );
   SCIP_CALL( SCIPsetEventhdlrExit(scip, eventhdlr, eventExitSync) );
 
   return SCIP_OKAY;
}
 
/** data for a concurrent solver type */
struct SCIP_ConcSolverTypeData
{
   SCIP_Bool             loademphasis;       /**< should emphasis settings be loaded when creating an instance of this concurrent solver */
   SCIP_PARAMEMPHASIS    emphasis;           /**< parameter emphasis that will be loaded if loademphasis is true */
};
 
/** data for a concurrent solver */
struct SCIP_ConcSolverData
{
   SCIP*                 solverscip;         /**< the concurrent solvers private SCIP data structure */
   SCIP_VAR**            vars;               /**< array of variables in the order of the main SCIP's variable array */
   int                   nvars;              /**< number of variables in the above arrays */
};
 
/** Disable dual reductions that might cut off optimal solutions. Although they keep at least
 *  one optimal solution intact, communicating these bounds may cut off all optimal solutions,
 *  if different optimal solutions were kept in different concurrent solvers. */
static
SCIP_RETCODE disableConflictingDualReductions(
   SCIP*                 scip                /**< SCIP data structure */
   )
{
   SCIP_Bool commvarbnds;
 
   SCIP_CALL( SCIPgetBoolParam(scip, "concurrent/commvarbnds", &commvarbnds) );
 
   if( !commvarbnds )
      return SCIP_OKAY;
 
   SCIP_CALL( SCIPsetBoolParam(scip, "misc/allowstrongdualreds", FALSE) );
 
   return SCIP_OKAY;
}
 
/** sets the child selection rule based on the index of the concurrent solver */
static
SCIP_RETCODE setChildSelRule(
   SCIP_CONCSOLVER*      concsolver          /**< the concurrent solver */
   )
{
   SCIP_CONCSOLVERDATA* data;
   static const char childsel[] = { 'h', 'i', 'p', 'r', 'l', 'd', 'u' };
 
   assert(concsolver != NULL);
 
   data = SCIPconcsolverGetData(concsolver);
   assert(data != NULL);
 
   SCIP_CALL( SCIPsetCharParam(data->solverscip, "nodeselection/childsel", childsel[SCIPconcsolverGetIdx(concsolver) % 7]) );
 
   return SCIP_OKAY;
}
 
/** initialize the concurrent SCIP solver, i.e., setup the copy of the problem and the
 *  mapping of the variables */
static
SCIP_RETCODE initConcsolver(
   SCIP*                 scip,               /**< the main SCIP instance */
   SCIP_CONCSOLVER*      concsolver          /**< the concurrent solver to set up */
   )
{
   SCIP_HASHMAP* varmapfw;
   SCIP_CONCSOLVERDATA* data;
   SCIP_VAR** mainvars;
   SCIP_VAR** mainfixedvars;
   SCIP_VAR** mainallvars;
   SCIP_Bool symmetrybefore;
   SCIP_Bool valid;
   int nmainvars;
   int nmainfixedvars;
   int* varperm;
   int cnt;
   int v;
 
   assert(scip != NULL);
   assert(concsolver != NULL);
 
   data = SCIPconcsolverGetData(concsolver);
   assert(data != NULL);
 
   /* we force the copying of symmetry constraints that may have been detected during a central presolving step;
    * otherwise, the copy may become invalid */
   SCIP_CALL( SCIPgetBoolParam(scip, "concurrent/symmetrybefore", &symmetrybefore) );
   if( symmetrybefore
      && ( SCIPsetBoolParam(scip, "constraints/orbitope_full/forceconscopy", TRUE) != SCIP_OKAY
      || SCIPsetBoolParam(scip, "constraints/orbitope_pp/forceconscopy", TRUE) != SCIP_OKAY
      || SCIPsetBoolParam(scip, "constraints/orbisack/forceconscopy", TRUE) != SCIP_OKAY
      || SCIPsetBoolParam(scip, "constraints/symresack/forceconscopy", TRUE) != SCIP_OKAY ) )
   {
      SCIPdebugMessage("Could not force copying of symmetry constraints\n");
   }
 
   /* get number of active variables in main SCIP */
   nmainvars = SCIPgetNVars(scip);
   mainvars = SCIPgetVars(scip);
 
   /* create the concurrent solver's SCIP instance and set up the problem */
   SCIP_CALL( SCIPcreate(&data->solverscip) );
   SCIPsetMessagehdlrQuiet(data->solverscip, SCIPmessagehdlrIsQuiet(SCIPgetMessagehdlr(scip)));
   SCIP_CALL( SCIPhashmapCreate(&varmapfw, SCIPblkmem(data->solverscip), nmainvars + SCIPgetNFixedVars(scip)) );
   SCIP_CALL( SCIPcopyConsCompression(scip, data->solverscip, varmapfw, NULL, SCIPconcsolverGetName(concsolver),
         NULL, NULL, 0, TRUE, FALSE, FALSE, FALSE, &valid) );
   assert(valid);
 
   /* include symmetry propagator if symmetry wasn't computed before and user wants symmetry */
   if( !symmetrybefore )
   {
      SCIP_CALL( SCIPincludePropSymmetry(data->solverscip) );
   }
 
   /* Note that because some aggregations or fixed variables cannot be resolved by some constraint handlers (in
    * particular cons_sos1, cons_sos2, cons_and), the copied problem may contain more variables than the original
    * problem has active variables. */
   data->nvars = SCIPgetNOrigVars(data->solverscip);
   assert( nmainvars <= data->nvars );
   assert(data->nvars <= SCIPgetNVars(scip) + SCIPgetNFixedVars(scip));
 
   /* allocate memory for the arrays to store the variable mapping */
   SCIP_CALL( SCIPallocBlockMemoryArray(data->solverscip, &data->vars, data->nvars) );
   SCIP_CALL( SCIPallocClearBufferArray(data->solverscip, &varperm, data->nvars) );
 
   /* In the following, we create a variable mapping between the solver and main SCIP variables. The mapping is created
    * by first retrieving the active variables, then the variables that are "fixed" in the main SCIP. This order is
    * taken because when performing SCIPcopyConsCompression, the active variables are copied first. This is followed by
    * the variables, which might involve (multi-)aggregated/fixed variables and coupling linear constraints. The
    * latter variables appear in the main SCIP as "fixed" variables. */
 
   /* set up the arrays for the variable mapping */
   SCIP_CALL( SCIPallocBufferArray(data->solverscip, &mainallvars, data->nvars) );
   for( v = 0; v < nmainvars; v++ )
   {
      SCIP_VAR* var;
      int idx;
 
      var = (SCIP_VAR*) SCIPhashmapGetImage(varmapfw, mainvars[v]);
      assert(var != NULL);
      idx = SCIPvarGetProbindex(var);
      assert(0 <= idx && idx < data->nvars);
 
      data->vars[v] = var;
      assert(varperm[idx] == 0);
      varperm[idx] = v;
 
      /* for copying solutions below */
      mainallvars[v] = mainvars[v];
   }
 
   nmainfixedvars = SCIPgetNFixedVars(scip);
   mainfixedvars = SCIPgetFixedVars(scip);
   cnt = nmainvars;
   for( v = 0; v < nmainfixedvars; v++ )
   {
      SCIP_VAR* var;
      int idx;
 
      var = (SCIP_VAR*) SCIPhashmapGetImage(varmapfw, mainfixedvars[v]);
      if( var != NULL )
      {
         idx = SCIPvarGetProbindex(var);
         if( idx >= 0 )
         {
            assert(idx < data->nvars);
 
            data->vars[cnt] = var;
            assert(varperm[idx] == 0);
            varperm[idx] = cnt;
 
            /* for copying solutions below */
            mainallvars[cnt] = mainfixedvars[v];
            ++cnt;
         }
      }
   }
   assert( cnt == data->nvars );
 
   /* transfer solutions from original problem to concurrent instances */
   if( SCIPgetNSols(scip) != 0 )
   {
      SCIP_Bool stored;
      SCIP_SOL* mainsol;
      SCIP_SOL* solversol;
 
      mainsol = SCIPgetBestSol(scip);
      SCIP_CALL( SCIPcreateSol(data->solverscip, &solversol, NULL) );
      for( v = 0; v < data->nvars; ++v )
      {
         SCIP_Real val;
 
         val = SCIPgetSolVal(scip, mainsol, mainallvars[v]);
         assert(data->vars[v] != NULL);
         SCIP_CALL( SCIPsetSolVal(data->solverscip, solversol, data->vars[v], val) );
      }
      SCIP_CALL( SCIPaddSolFree(data->solverscip, &solversol, &stored) );
      assert(stored);
   }
 
   /* create the concurrent data structure for the concurrent solver's SCIP */
   SCIP_CALL( SCIPcreateConcurrent(data->solverscip, concsolver, varperm, data->nvars) );
   SCIPfreeBufferArray(data->solverscip, &mainallvars);
   SCIPfreeBufferArray(data->solverscip, &varperm);
 
   /* free the hashmap */
   SCIPhashmapFree(&varmapfw);
 
   return SCIP_OKAY;
}
 
/** creates an instance of a concurrent SCIP solver */
static
SCIP_DECL_CONCSOLVERCREATEINST(concsolverScipCreateInstance)
{
   char filename[SCIP_MAXSTRLEN];
   SCIP_CONCSOLVERDATA* data;
   SCIP_CONCSOLVERTYPEDATA* typedata;
   SCIP_Bool changechildsel;
   char* prefix;
 
   assert(scip != NULL);
   assert(concsolvertype != NULL);
   assert(concsolver != NULL);
 
   typedata = SCIPconcsolverTypeGetData(concsolvertype);
 
   SCIP_ALLOC( BMSallocMemory(&data) );
   SCIPconcsolverSetData(concsolver, data);
 
   SCIP_CALL( initConcsolver(scip, concsolver) );
 
   /* check if emphasis setting should be loaded */
   if( typedata->loademphasis )
   {
      SCIP_PARAM** params;
      SCIP_PARAM** fixedparams;
      int nparams;
      int nfixedparams;
      int i;
 
      params = SCIPgetParams(data->solverscip);
      nparams = SCIPgetNParams(data->solverscip);
      SCIP_CALL( SCIPallocBufferArray(data->solverscip, &fixedparams, nparams) );
      nfixedparams = 0;
 
      /* fix certain parameters before loading emphasis to avoid setting them to default values */
      for( i = 0; i < nparams; ++i )
      {
         const char* paramname;
 
         paramname = SCIPparamGetName(params[i]);
 
         if( strncmp(paramname, "limits/", 7) == 0 ||
             strncmp(paramname, "numerics/", 9) == 0 ||
             strncmp(paramname, "memory/", 7) == 0 ||
             strncmp(paramname, "concurrent/sync/", 16) == 0 ||
             strncmp(paramname, "heuristics/sync/", 16) == 0 ||
             strncmp(paramname, "propagating/sync/", 17) == 0 )
         {
            fixedparams[nfixedparams++] = params[i];
            SCIP_CALL( SCIPfixParam(data->solverscip, paramname) );
         }
      }
 
      SCIP_CALL( SCIPsetEmphasis(data->solverscip, typedata->emphasis, TRUE) );
 
      for( i = 0; i < nfixedparams; ++i )
         SCIP_CALL( SCIPunfixParam(data->solverscip, SCIPparamGetName(fixedparams[i])) );
 
      SCIPfreeBufferArray(data->solverscip, &fixedparams);
   }
 
   /* load settings file if it exists */
   SCIP_CALL( SCIPgetStringParam(scip, "concurrent/paramsetprefix", &prefix) );
   (void) SCIPsnprintf(filename, SCIP_MAXSTRLEN, "%s%s.set", prefix, SCIPconcsolverGetName(concsolver));
 
   if( SCIPfileExists(filename) )
   {
      /* load settings file and print info message */
      SCIPinfoMessage(scip, NULL, "reading parameter file <%s> for concurrent solver <%s>\n", filename, SCIPconcsolverGetName(concsolver));
      SCIP_CALL( SCIPreadParams(data->solverscip, filename) );
   }
   else
   {
      /* print message about missing setting files only in verblevel full */
      SCIPverbMessage(scip, SCIP_VERBLEVEL_FULL, NULL, "skipping non existent parameter file <%s> for concurrent solver <%s>\n",
         filename, SCIPconcsolverGetName(concsolver));
   }
 
   /* include eventhandler for synchronization */
   SCIP_CALL( includeEventHdlrSync(data->solverscip) );
 
   /* disable output for subscip */
   SCIP_CALL( SCIPsetIntParam(data->solverscip, "display/verblevel", 0) );
 
   /* use wall clock time in subscips */
   SCIP_CALL( SCIPsetIntParam(data->solverscip, "timing/clocktype", (int)SCIP_CLOCKTYPE_WALL) );
 
   /* don't catch ctrlc since already caught in main SCIP */
   SCIP_CALL( SCIPsetBoolParam(data->solverscip, "misc/catchctrlc", FALSE) );
 
   /* one solver can do all dual reductions and share them with the other solvers */
   if( SCIPconcsolverGetIdx(concsolver) != 0 )
   {
      SCIP_CALL( disableConflictingDualReductions(data->solverscip) );
   }
 
   /* set different child selection rules if corresponding parameter is TRUE */
   SCIP_CALL( SCIPgetBoolParam(scip, "concurrent/changechildsel", &changechildsel) );
   if( changechildsel )
   {
      SCIP_CALL( setChildSelRule(concsolver) );
   }
 
   return SCIP_OKAY;
}
 
/** destroys an instance of a concurrent SCIP solver */
static
SCIP_DECL_CONCSOLVERDESTROYINST(concsolverScipDestroyInstance)
{
   SCIP_CONCSOLVERDATA* data;
 
   assert(concsolver != NULL);
 
   data = SCIPconcsolverGetData(concsolver);
   assert(data != NULL);
   assert(data->solverscip != NULL);
 
   /* free the array with the variable mapping */
   SCIPfreeBlockMemoryArray(data->solverscip, &data->vars, data->nvars);
 
   /* free subscip */
   SCIP_CALL( SCIPfree(&data->solverscip) );
   BMSfreeMemory(&data);
   SCIPconcsolverSetData(concsolver, NULL);
 
   return SCIP_OKAY;
}
 
/** frees the data of a concurrent solver type */
static
SCIP_DECL_CONCSOLVERTYPEFREEDATA(concsolverTypeScipFreeData)
{
   assert(data != NULL);
   BMSfreeMemory(data);
}
 
/** initializes the random and permutation seeds and enables permutation of constraints and variables */
static
SCIP_DECL_CONCSOLVERINITSEEDS(concsolverScipInitSeeds)
{
   SCIP_CONCSOLVERDATA* data;
 
   assert(concsolver != NULL);
 
   data = SCIPconcsolverGetData(concsolver);
   assert(data != NULL);
 
   SCIPinfoMessage(data->solverscip, NULL, "initializing seeds to %d in concurrent solver '%s'\n", (int) seed, SCIPconcsolverGetName(concsolver));
 
   SCIP_CALL( SCIPsetIntParam(data->solverscip, "randomization/randomseedshift", (int) seed) );
   SCIP_CALL( SCIPsetIntParam(data->solverscip, "randomization/permutationseed", (int) seed) );
   SCIP_CALL( SCIPsetBoolParam(data->solverscip, "randomization/permutevars", TRUE) );
   SCIP_CALL( SCIPsetBoolParam(data->solverscip, "randomization/permuteconss", TRUE) );
 
   return SCIP_OKAY;
}
 
/** extracts solving status of this concurrent solver and the solving statistics
 *  into the given SCIP instance
 */
static
SCIP_DECL_CONCSOLVERCOPYSOLVINGDATA(concsolverGetSolvingData)
{
   SCIP_CONCSOLVERDATA* data;
   int nsols;
 
   assert(scip != NULL);
   assert(concsolver != NULL);
 
   data = SCIPconcsolverGetData(concsolver);
   assert(data != NULL);
   assert(data->solverscip != NULL);
 
   nsols = SCIPgetNSols(data->solverscip);
   if( nsols > 0 )
   {
      SCIP_VAR** mainvars;
      SCIP_SOL** solversols;
      SCIP_Real* solvals;
      int nmainvars;
      int i;
 
      mainvars = SCIPgetVars(scip);
      nmainvars = SCIPgetNVars(scip);
      assert(nmainvars <= data->nvars);
 
      solversols = SCIPgetSols(data->solverscip);
 
      /* allocate buffer array used for translating the solution to the given SCIP */
      SCIP_CALL( SCIPallocBufferArray(scip, &solvals, nmainvars) );
 
      /* add the solutions to the given SCIP */
      for( i = 0; i < nsols; ++i )
      {
         SCIP_SOL* mainsol;
         SCIP_HEUR* heur;
         SCIP_Bool stored;
 
         /* only get the first nmainvars, which correspond to the active variables */
         SCIP_CALL( SCIPgetSolVals(data->solverscip, solversols[i], nmainvars, data->vars, solvals) );
 
         heur = SCIPsolGetHeur(solversols[i]);
         if( heur != NULL )
            heur = SCIPfindHeur(scip, SCIPheurGetName(heur));
 
         SCIP_CALL( SCIPcreateSol(scip, &mainsol, heur) );
         SCIP_CALL( SCIPsetSolVals(scip, mainsol, nmainvars, mainvars, solvals) );
         SCIP_CALL( SCIPcopySolStats(solversols[i], mainsol) );
 
#ifdef SCIP_CHECK_MAINSCIP_SOLUTION
         /* The following sometimes fails because we do not copy aggregations and cons_fixedvar can reject solutions in
          * mainscip, because of these. */
         {
            SCIP_Bool feasible;
            SCIP_CALL( SCIPcheckSol(scip, mainsol, TRUE, TRUE, TRUE, TRUE, FALSE, &feasible) );
            assert( feasible );
         }
#endif
 
         SCIP_CALL( SCIPaddSolFree(scip, &mainsol, &stored) );
      }
 
      /* free the buffer array */
      SCIPfreeBufferArray(scip, &solvals);
   }
 
   /* copy solving statistics and status from the solver SCIP to the given SCIP */
   SCIP_CALL( SCIPcopyConcurrentSolvingStats(data->solverscip, scip) );
 
   return SCIP_OKAY;
}
 
/** execution method of SCIP concsolver solver
 *
 *  Start solving the problem until the solving reaches a limit, gets interrupted, or just finished successfully.
 */
static
SCIP_DECL_CONCSOLVEREXEC(concsolverScipExec)
{
   SCIP_CONCSOLVERDATA* data;
 
   assert(concsolver != NULL);
   assert(solvingtime != NULL);
   assert(nlpiterations != NULL);
   assert(nnodes != NULL);
 
   data = SCIPconcsolverGetData(concsolver);
   assert(data != NULL);
 
   /* print info message that solving has started */
   SCIPinfoMessage(data->solverscip, NULL, "starting solve in concurrent solver '%s'\n", SCIPconcsolverGetName(concsolver));
 
   /* solve */
   SCIP_CALL( SCIPsolve(data->solverscip) );
 
   /* first output time */
   SCIPinfoMessage(data->solverscip, NULL, " ");
   SCIPdispTime(SCIPgetMessagehdlr(data->solverscip), NULL, SCIPgetSolvingTime(data->solverscip), 5);
   /* print info message with status */
   SCIPinfoMessage(data->solverscip, NULL, ": concurrent solver '%s' stopped with status ", SCIPconcsolverGetName(concsolver));
   SCIP_CALL( SCIPprintStatus(data->solverscip, NULL) );
   SCIPinfoMessage(data->solverscip, NULL, "\n");
 
   /* set solving statistics */
   *solvingtime = SCIPgetSolvingTime(data->solverscip);
   *nlpiterations = SCIPgetNLPIterations(data->solverscip);
   *nnodes = SCIPgetNNodes(data->solverscip);
 
   return SCIP_OKAY;
}
 
/** stops the concurrent solver as soon as possible */
static
SCIP_DECL_CONCSOLVERSTOP(concsolverScipStop)
{
   SCIP_CONCSOLVERDATA* data;
 
   assert(concsolver != NULL);
 
   data = SCIPconcsolverGetData(concsolver);
   assert(data != NULL);
 
   SCIP_CALL( SCIPinterruptSolve(data->solverscip) );
 
   return SCIP_OKAY;
}
 
/** writes new solutions and global boundchanges to the given synchronization data */
static
SCIP_DECL_CONCSOLVERSYNCWRITE(concsolverScipSyncWrite)
{
   SCIP_SOL** sols;
   SCIP_CONCSOLVERDATA* data;
   SCIP_BOUNDSTORE* boundstore;
   SCIP_STATUS solverstatus;
   int concsolverid;
   int nsols;
   int i;
 
   assert(concsolver != NULL);
   assert(syncstore != NULL);
   assert(syncdata != NULL);
   assert(nsolsshared != NULL);
 
   *nsolsshared = 0;
 
   if ( maxcandsols <= 0 )
      return SCIP_OKAY;
 
   if( SCIPsyncdataGetStatus(syncdata) != SCIP_STATUS_UNKNOWN )
      return SCIP_OKAY;
 
   data = SCIPconcsolverGetData(concsolver);
   assert(data != NULL);
   assert(data->solverscip != NULL);
   concsolverid = SCIPconcsolverGetIdx(concsolver);
   solverstatus = SCIPgetStatus(data->solverscip);
 
   SCIPsyncdataSetStatus(syncdata, solverstatus, concsolverid);
   SCIPsyncdataSetLowerbound(syncdata, SCIPgetDualbound(data->solverscip));
   SCIPsyncdataSetUpperbound(syncdata, SCIPgetPrimalbound(data->solverscip));
 
   SCIPdebugMessage("syncing in concurrent solver %s\n", SCIPconcsolverGetName(concsolver));
 
   /* consider at most maxcandsols many solutions, and since the solution array is sorted, consider best solutions */
   nsols = SCIPgetNSols(data->solverscip);
   nsols = MIN(nsols, maxcandsols);
   sols = SCIPgetSols(data->solverscip);
 
   for( i = 0; i < nsols; ++i )
   {
      if( SCIPIsConcurrentSolNew(data->solverscip, sols[i]) )
      {
         SCIP_Real solobj;
         SCIP_Real* solvals;
 
         solobj = SCIPgetSolOrigObj(data->solverscip, sols[i]);
 
         SCIPdebugMessage("adding sol in concurrent solver %s\n", SCIPconcsolverGetName(concsolver));
         SCIPsyncdataGetSolutionBuffer(syncstore, syncdata, solobj, concsolverid, &solvals);
 
         /* if syncstore has no place for this solution, we can stop, since the next solution will have
          * a worse objective value and thus won't be accepted either
          */
         if( solvals == NULL )
            break;
 
         ++(*nsolsshared);
         SCIP_CALL( SCIPgetSolVals(data->solverscip, sols[i], data->nvars, data->vars, solvals) );
 
         /* if we have added the maximum number of solutions we can also stop */
         if( *nsolsshared == maxsharedsols )
            break;
      }
   }
 
   boundstore = SCIPgetConcurrentGlobalBoundChanges(data->solverscip);
 
   if( boundstore != NULL )
   {
      SCIP_CALL( SCIPsyncdataAddBoundChanges(syncstore, syncdata, boundstore) );
   }
 
   SCIPsyncdataAddMemTotal(syncdata, SCIPgetMemTotal(data->solverscip));
 
   return SCIP_OKAY;
}
 
/** reads the solutions and bounds from the given synchronization data */
static
SCIP_DECL_CONCSOLVERSYNCREAD(concsolverScipSyncRead)
{  /*lint --e{715}*/
   SCIP_Real** solvals;
   SCIP_CONCSOLVERDATA* data;
   SCIP_BOUNDSTORE* boundstore;
   int* concsolverids;
   int concsolverid;
   int nbndchgs;
   int nsols;
   int i;
 
   assert(concsolver != NULL);
   assert(syncstore != NULL);
   assert(syncdata != NULL);
   assert(nsolsrecvd != NULL);
   assert(ntighterbnds != NULL);
   assert(ntighterintbnds != NULL);
 
   *nsolsrecvd = 0;
 
   data = SCIPconcsolverGetData(concsolver);
   assert(data != NULL);
 
   concsolverid = SCIPconcsolverGetIdx(concsolver);
 
   /* get solutions from synchronization data */
   SCIPsyncdataGetSolutions(syncdata, &solvals, &concsolverids, &nsols);
   for( i = 0; i < nsols; ++i )
   {
      SCIP_SOL* newsol;
      SCIP_Bool feasible;
 
      /* do not add own solutions */
      if( concsolverids[i] == concsolverid )
         continue;
 
      /* solution is from another solver, so translate to this solver's variable space and add it to SCIP */
      ++(*nsolsrecvd);
      SCIP_CALL( SCIPcreateOrigSol(data->solverscip, &newsol, NULL) );
      SCIP_CALL( SCIPsetSolVals(data->solverscip, newsol, data->nvars, data->vars, solvals[i]) );
 
      /* check whether solution is feasible */
      SCIP_CALL( SCIPcheckSol(data->solverscip, newsol, FALSE, FALSE, TRUE, TRUE, FALSE, &feasible) );
 
      if( feasible )
      {
         SCIPdebugMessage("adding solution in concurrent solver %s\n", SCIPconcsolverGetName(concsolver));
         SCIP_CALL( SCIPaddConcurrentSol(data->solverscip, newsol) );
      }
   }
 
   /* get bound changes from the synchronization data and add it to this concurrent solvers SCIP */
   *ntighterbnds = 0;
   *ntighterintbnds = 0;
   boundstore = SCIPsyncdataGetBoundChgs(syncdata);
   nbndchgs = SCIPboundstoreGetNChgs(boundstore);
 
   for( i = 0; i < nbndchgs; ++i )
   {
      SCIP_VAR* var;
      SCIP_BOUNDTYPE boundtype;
      SCIP_Real newbound;
      int idx;
 
      idx = SCIPboundstoreGetChgVaridx(boundstore, i);
      assert(0 <= idx && idx < data->nvars);
      var = data->vars[idx];
      boundtype = SCIPboundstoreGetChgType(boundstore, i);
      newbound = SCIPboundstoreGetChgVal(boundstore, i);
 
      SCIP_CALL( SCIPvarGetProbvarBound(&var, &newbound, &boundtype) );
 
      /* cannot change bounds of multi-aggregated variables so do not pass this bound-change to the propagator */
      if( SCIPvarGetStatus(var) == SCIP_VARSTATUS_MULTAGGR )
         return SCIP_OKAY;
 
      /* if bound is not better then do not pass this bound and do not waste memory for storing this boundchange */
      if( boundtype == SCIP_BOUNDTYPE_LOWER && SCIPisGE(data->solverscip, SCIPvarGetLbGlobal(var), newbound) )
         return SCIP_OKAY;
 
      if( boundtype == SCIP_BOUNDTYPE_UPPER && SCIPisLE(data->solverscip, SCIPvarGetUbGlobal(var), newbound) )
         return SCIP_OKAY;
 
      /* bound is better so incremented counters for statistics and pass it to the sync propagator */
      ++(*ntighterbnds);
 
      if( SCIPvarIsNonimpliedIntegral(var) )
         ++(*ntighterintbnds);
 
      SCIP_CALL( SCIPaddConcurrentBndchg(data->solverscip, var, newbound, boundtype) );
   }
 
   return SCIP_OKAY;
}
 
 
/** creates the concurrent SCIP solver plugins and includes them in SCIP */
SCIP_RETCODE SCIPincludeConcurrentScipSolvers(
   SCIP*                 scip                /**< SCIP data structure */
   )
{
   SCIP_CONCSOLVERTYPEDATA* data;
 
   assert(scip != NULL);
 
   /* Include concurrent solvers for SCIP for all emphasis settings and without an emphasis setting.
    * For the SCIP without an emphasis setting we set the default preferred priority to 1 and for the other types to 0
    * so that the default concurrent solve will use multiple SCIP's using settings as specified by the user in the main SCIP.
    */
   SCIP_CALL( SCIPallocMemory(scip, &data) );
   data->loademphasis = FALSE;
   SCIP_CALL( SCIPincludeConcsolverType(scip, "scip", 1.0, concsolverScipCreateInstance, concsolverScipDestroyInstance, concsolverScipInitSeeds,
         concsolverScipExec, concsolverGetSolvingData, concsolverScipStop, concsolverScipSyncWrite,
         concsolverScipSyncRead, concsolverTypeScipFreeData, data) );
 
   SCIP_CALL( SCIPallocMemory(scip, &data) );
   data->loademphasis = TRUE;
   data->emphasis = SCIP_PARAMEMPHASIS_DEFAULT;
   SCIP_CALL( SCIPincludeConcsolverType(scip, "scip-default", 0.0, concsolverScipCreateInstance, concsolverScipDestroyInstance, concsolverScipInitSeeds,
         concsolverScipExec, concsolverGetSolvingData, concsolverScipStop, concsolverScipSyncWrite,
         concsolverScipSyncRead, concsolverTypeScipFreeData, data) );
 
   SCIP_CALL( SCIPallocMemory(scip, &data) );
   data->loademphasis = TRUE;
   data->emphasis = SCIP_PARAMEMPHASIS_CPSOLVER;
   SCIP_CALL( SCIPincludeConcsolverType(scip, "scip-cpsolver", 0.0, concsolverScipCreateInstance, concsolverScipDestroyInstance, concsolverScipInitSeeds,
         concsolverScipExec, concsolverGetSolvingData, concsolverScipStop, concsolverScipSyncWrite,
         concsolverScipSyncRead, concsolverTypeScipFreeData, data) );
 
   SCIP_CALL( SCIPallocMemory(scip, &data) );
   data->loademphasis = TRUE;
   data->emphasis = SCIP_PARAMEMPHASIS_EASYCIP;
   SCIP_CALL( SCIPincludeConcsolverType(scip, "scip-easycip", 0.0, concsolverScipCreateInstance, concsolverScipDestroyInstance, concsolverScipInitSeeds,
         concsolverScipExec, concsolverGetSolvingData, concsolverScipStop, concsolverScipSyncWrite,
         concsolverScipSyncRead, concsolverTypeScipFreeData, data) );
 
   SCIP_CALL( SCIPallocMemory(scip, &data) );
   data->loademphasis = TRUE;
   data->emphasis = SCIP_PARAMEMPHASIS_FEASIBILITY;
   SCIP_CALL( SCIPincludeConcsolverType(scip, "scip-feas", 0.0, concsolverScipCreateInstance, concsolverScipDestroyInstance, concsolverScipInitSeeds,
         concsolverScipExec, concsolverGetSolvingData, concsolverScipStop, concsolverScipSyncWrite,
         concsolverScipSyncRead, concsolverTypeScipFreeData, data) );
 
   SCIP_CALL( SCIPallocMemory(scip, &data) );
   data->loademphasis = TRUE;
   data->emphasis = SCIP_PARAMEMPHASIS_HARDLP;
   SCIP_CALL( SCIPincludeConcsolverType(scip, "scip-hardlp", 0.0, concsolverScipCreateInstance, concsolverScipDestroyInstance, concsolverScipInitSeeds,
         concsolverScipExec, concsolverGetSolvingData, concsolverScipStop, concsolverScipSyncWrite,
         concsolverScipSyncRead, concsolverTypeScipFreeData, data) );
 
   SCIP_CALL( SCIPallocMemory(scip, &data) );
   data->loademphasis = TRUE;
   data->emphasis = SCIP_PARAMEMPHASIS_OPTIMALITY;
   SCIP_CALL( SCIPincludeConcsolverType(scip, "scip-opti", 0.0, concsolverScipCreateInstance, concsolverScipDestroyInstance, concsolverScipInitSeeds,
         concsolverScipExec, concsolverGetSolvingData, concsolverScipStop, concsolverScipSyncWrite,
         concsolverScipSyncRead, concsolverTypeScipFreeData, data) );
 
   SCIP_CALL( SCIPallocMemory(scip, &data) );
   data->loademphasis = TRUE;
   data->emphasis = SCIP_PARAMEMPHASIS_COUNTER;
   SCIP_CALL( SCIPincludeConcsolverType(scip, "scip-counter", 0.0,  concsolverScipCreateInstance, concsolverScipDestroyInstance, concsolverScipInitSeeds,
         concsolverScipExec, concsolverGetSolvingData, concsolverScipStop, concsolverScipSyncWrite,
         concsolverScipSyncRead, concsolverTypeScipFreeData, data) );
 
   return SCIP_OKAY;
}