Exemplo n.º 1
0
/** presolving execution method */
static
SCIP_DECL_PRESOLEXEC(presolExecBoundshift)
{  /*lint --e{715}*/
   SCIP_PRESOLDATA* presoldata;
   SCIP_VAR** scipvars;
   SCIP_VAR** vars;
   int nbinvars;
   int nvars;
   int v;

   assert(scip != NULL);
   assert(presol != NULL);
   assert(strcmp(SCIPpresolGetName(presol), PRESOL_NAME) == 0);
   assert(result != NULL);

   *result = SCIP_DIDNOTRUN;

   /* get presolver data */
   presoldata = SCIPpresolGetData(presol);
   assert(presoldata != NULL);
   
   /* get the problem variables */
   scipvars = SCIPgetVars(scip);
   nbinvars = SCIPgetNBinVars(scip);
   nvars = SCIPgetNVars(scip) - nbinvars;

   if( nvars == 0 )
      return SCIP_OKAY;
   
   if( SCIPdoNotAggr(scip) )
      return SCIP_OKAY;

   *result = SCIP_DIDNOTFIND;

   /* copy the integer variables into an own array, since adding new integer variables affects the left-most slots in
    * the array and thereby interferes with our search loop
    */
   SCIP_CALL( SCIPduplicateBufferArray(scip, &vars, &scipvars[nbinvars], nvars) );
   
   /* scan the integer, implicit, and continuous variables for possible conversion */
   for( v = nvars - 1; v >= 0; --v )
   {
      SCIP_VAR* var = vars[v];
      SCIP_Real lb;
      SCIP_Real ub;

      assert(SCIPvarGetType(var) != SCIP_VARTYPE_BINARY);

      /* get current variable's bounds */
      lb = SCIPvarGetLbGlobal(var);
      ub = SCIPvarGetUbGlobal(var);

      assert( SCIPisLE(scip, lb, ub) );
      if( SCIPisEQ(scip, lb, ub) )
         continue;
      if( presoldata->integer && !SCIPisIntegral(scip, ub - lb) ) 
         continue;

      /* check if bounds are shiftable */
      if( !SCIPisEQ(scip, lb, 0.0) &&                           /* lower bound != 0.0 */
         SCIPisLT(scip, ub, SCIPinfinity(scip)) &&              /* upper bound != infinity */
         SCIPisGT(scip, lb, -SCIPinfinity(scip)) &&             /* lower bound != -infinity */
#if 0
         SCIPisLT(scip, ub - lb, SCIPinfinity(scip)) &&         /* interval length less than SCIPinfinity(scip) */
#endif
         SCIPisLT(scip, ub - lb, (SCIP_Real) presoldata->maxshift) )        /* less than max shifting */
      {
         SCIP_VAR* newvar;
         char newvarname[SCIP_MAXSTRLEN];
         SCIP_Bool infeasible;
         SCIP_Bool redundant;
         SCIP_Bool aggregated;

         SCIPdebugMessage("convert range <%s>[%g,%g] to [%g,%g]\n", SCIPvarGetName(var), lb, ub, 0.0, (ub - lb) );

         /* create new variable */
         (void) SCIPsnprintf(newvarname, SCIP_MAXSTRLEN, "%s_shift", SCIPvarGetName(var));
         SCIP_CALL( SCIPcreateVar(scip, &newvar, newvarname, 0.0, (ub - lb), 0.0, SCIPvarGetType(var),
               SCIPvarIsInitial(var), SCIPvarIsRemovable(var), NULL, NULL, NULL, NULL, NULL) );
         SCIP_CALL( SCIPaddVar(scip, newvar) );

         /* aggregate old variable with new variable */
         if( presoldata->flipping )
         {
            if( REALABS(ub) < REALABS(lb) )
            {
               SCIP_CALL( SCIPaggregateVars(scip, var, newvar, 1.0, 1.0, ub, &infeasible, &redundant, &aggregated) );
            }
            else
            {
               SCIP_CALL( SCIPaggregateVars(scip, var, newvar, 1.0, -1.0, lb, &infeasible, &redundant, &aggregated) );
            }
         }
         else
         {
            SCIP_CALL( SCIPaggregateVars(scip, var, newvar, 1.0, -1.0, lb, &infeasible, &redundant, &aggregated) );
         }

         assert(!infeasible);
         assert(redundant);
         assert(aggregated);
         SCIPdebugMessage("var <%s> with bounds [%f,%f] has obj %f\n",
            SCIPvarGetName(newvar),SCIPvarGetLbGlobal(newvar),SCIPvarGetUbGlobal(newvar),SCIPvarGetObj(newvar));

         /* release variable */
         SCIP_CALL( SCIPreleaseVar(scip, &newvar) );
         
         /* take care of statistic */
         (*naggrvars)++;
         *result = SCIP_SUCCESS;
      }
   }

   /* free temporary memory */
   SCIPfreeBufferArray(scip, &vars);
   
   return SCIP_OKAY;
}
/** presolving execution method */
static
SCIP_DECL_PRESOLEXEC(presolExecInttobinary)
{  /*lint --e{715}*/
   SCIP_VAR** scipvars;
   SCIP_VAR** vars;
   int nbinvars;
   int nintvars;
   int v;

   assert(result != NULL);

   *result = SCIP_DIDNOTRUN;

   if( SCIPdoNotAggr(scip) )
      return SCIP_OKAY;

   /* get the problem variables */
   scipvars = SCIPgetVars(scip);
   nbinvars = SCIPgetNBinVars(scip);
   nintvars = SCIPgetNIntVars(scip);
   if( nintvars == 0 )
      return SCIP_OKAY;

   *result = SCIP_DIDNOTFIND;

   /* copy the integer variables into an own array, since adding binary variables affects the left-most slots in the
    * array and thereby interferes with our search loop
    */
   SCIP_CALL( SCIPduplicateBufferArray(scip, &vars, &scipvars[nbinvars], nintvars) );

   /* scan the integer variables for possible conversion into binaries;
    * we have to collect the variables first in an own 
    */
   for( v = 0; v < nintvars; ++v )
   {
      SCIP_Real lb;
      SCIP_Real ub;

      assert(SCIPvarGetType(vars[v]) == SCIP_VARTYPE_INTEGER);

      /* get variable's bounds */
      lb = SCIPvarGetLbGlobal(vars[v]);
      ub = SCIPvarGetUbGlobal(vars[v]);

      /* check if bounds are exactly one apart */
      if( SCIPisEQ(scip, lb, ub - 1.0) )
      {
         SCIP_VAR* binvar;
         char binvarname[SCIP_MAXSTRLEN];
         SCIP_Bool infeasible;
         SCIP_Bool redundant;
         SCIP_Bool aggregated;

         SCIPdebugMessage("converting <%s>[%g,%g] into binary variable\n", SCIPvarGetName(vars[v]), lb, ub);

         /* create binary variable */
         (void) SCIPsnprintf(binvarname, SCIP_MAXSTRLEN, "%s_bin", SCIPvarGetName(vars[v]));
         SCIP_CALL( SCIPcreateVar(scip, &binvar, binvarname, 0.0, 1.0, 0.0, SCIP_VARTYPE_BINARY,
               SCIPvarIsInitial(vars[v]), SCIPvarIsRemovable(vars[v]), NULL, NULL, NULL, NULL, NULL) );
         SCIP_CALL( SCIPaddVar(scip, binvar) );

         /* aggregate integer and binary variable */
         SCIP_CALL( SCIPaggregateVars(scip, vars[v], binvar, 1.0, -1.0, lb, &infeasible, &redundant, &aggregated) );

         /* release binary variable */
         SCIP_CALL( SCIPreleaseVar(scip, &binvar) );

         /* it can be the case that this aggregation detects an infeasibility; for example, during the copy of the
          * variable bounds from the integer variable to the binary variable, infeasibility can be detected; this can
          * happen because an upper bound or a lower bound of such a variable bound variable was "just" changed and the
          * varbound constraint handler, who would detect that infeasibility (since it was creating it from a varbound
          * constraint), was called before that bound change was detected due to the presolving priorities;
          */
         if( infeasible )
         {
            *result = SCIP_CUTOFF;
            break;
         }
            
         assert(redundant);
         assert(aggregated);
         (*nchgvartypes)++;
         *result = SCIP_SUCCESS;
      }
   }

   /* free temporary memory */
   SCIPfreeBufferArray(scip, &vars);

   return SCIP_OKAY;
}
Exemplo n.º 3
0
/** execution method of presolver */
static
SCIP_DECL_PRESOLEXEC(presolExecDualagg)
{  /*lint --e{715}*/
   SCIPMILPMATRIX* matrix;
   SCIP_Bool initialized;
   SCIP_Bool complete;

   assert(result != NULL);
   *result = SCIP_DIDNOTRUN;

   if( (SCIPgetStage(scip) != SCIP_STAGE_PRESOLVING) || SCIPinProbing(scip) || SCIPisNLPEnabled(scip) )
      return SCIP_OKAY;

   if( SCIPisStopped(scip) || SCIPgetNActivePricers(scip) > 0 )
      return SCIP_OKAY;

   if( SCIPgetNBinVars(scip) == 0 )
      return SCIP_OKAY;

   if( !SCIPallowDualReds(scip) )
      return SCIP_OKAY;

   *result = SCIP_DIDNOTFIND;

   matrix = NULL;
   SCIP_CALL( SCIPmatrixCreate(scip, &matrix, &initialized, &complete) );

   /* we only work on pure MIPs currently */
   if( initialized && complete )
   {
      AGGRTYPE* aggtypes;
      SCIP_VAR** binvars;
      int nvaragg;
      int ncols;

      ncols = SCIPmatrixGetNColumns(matrix);
      nvaragg = 0;

      SCIP_CALL( SCIPallocBufferArray(scip, &aggtypes, ncols) );
      BMSclearMemoryArray(aggtypes, ncols);

      SCIP_CALL( SCIPallocBufferArray(scip, &binvars, ncols) );
      SCIPdebug( BMSclearMemoryArray(binvars, ncols) );

      /* search for aggregations */
      SCIP_CALL( findUplockAggregations(scip, matrix, &nvaragg, aggtypes, binvars) );
      SCIP_CALL( findDownlockAggregations(scip, matrix, &nvaragg, aggtypes, binvars) );

      /* apply aggregations, if we found any */
      if( nvaragg > 0 )
      {
         int v;

         for( v = 0; v < ncols; v++ )
         {
            if( aggtypes[v] != NOAGG )
            {
               SCIP_Bool infeasible;
               SCIP_Bool redundant;
               SCIP_Bool aggregated;
               SCIP_Real ub;
               SCIP_Real lb;

               ub = SCIPmatrixGetColUb(matrix, v);
               lb = SCIPmatrixGetColLb(matrix, v);

               /* aggregate variable */
               assert(binvars[v] != NULL);
               if( aggtypes[v] == BIN0UBOUND )
               {
                  SCIP_CALL( SCIPaggregateVars(scip, SCIPmatrixGetVar(matrix, v), binvars[v], 1.0, ub-lb,
                        ub, &infeasible, &redundant, &aggregated) );
               }
               else
               {
                  assert(aggtypes[v] == BIN0LBOUND);
                  SCIP_CALL( SCIPaggregateVars(scip, SCIPmatrixGetVar(matrix, v), binvars[v], 1.0, lb-ub,
                        lb, &infeasible, &redundant, &aggregated) );
               }

               /* infeasible aggregation */
               if( infeasible )
               {
                  SCIPdebugMessage(" -> infeasible aggregation\n");
                  *result = SCIP_CUTOFF;
                  return SCIP_OKAY;
               }

               if( aggregated )
                  (*naggrvars)++;
            }
         }

         /* set result pointer */
         if( (*naggrvars) > 0 )
            *result = SCIP_SUCCESS;
      }

      SCIPfreeBufferArray(scip, &binvars);
      SCIPfreeBufferArray(scip, &aggtypes);
   }

   SCIPmatrixFree(scip, &matrix);

   return SCIP_OKAY;
}