Hi,

I'm a student currently evaluating Drools Solver for my dissertation. I am currently trying to solve an optimization problem with two different solvers (one of which is Drools Solver) and I am comparing the results with earlier obtained results from literature. However I am having some troubles with the performance of Drools Solver, and I was hoping if someone could look at my rules to see if they could be tuned:

rule "patientsToBeAssignedToRoomsOfAppropriateSex"
        when
                $n : Night();
                $room : Room(sexRestriction == Sex.Dependent && capacity > 1);
                $genders : ArrayList(size>1) from collect( PatientStay(bed.room == $room, night == $n) );
                exists PatientStay(bed.room == $room, night == $n, $a : admission, eval(((PatientStay)$genders.get(0)).getAdmission().getPatient().getSex() != $a.getPatient().getSex()));
        then
                insertLogical(new IntConstraintOccurrence("patientsToBeAssignedToRoomsOfAppropriateSex",ConstraintType.NEGATIVE_HARD,50,$room,$n));
end

rule "hasRequiredRoomProperties"
        when
                $pr : RequiredRoomPropertiesConstraint($a : admission, $r : room, $w : weight );
                $ps : PatientStay(admission == $a, bed.room == $r);
        then
                insertLogical(new IntConstraintOccurrence("hasPreferredRoomProperties",ConstraintType.NEGATIVE_SOFT,50*$w,$ps));
end

rule "unplannedTransfers"
        when
                $ps : PatientStay($a : admission, $b : bed, $n : night);
                $ps2 : PatientStay(admission == $a, bed != $b, $n2 : night,eval($n.getIndex()+1 == $n2.getIndex()));
        then
                insertLogical(new IntConstraintOccurrence("unplannedTransfers",ConstraintType.NEGATIVE_SOFT,110,$ps,$ps2));
end

rule "hasPreferredRoomProperties"
        when
                $pr : PreferredRoomPropertiesConstraint($a : admission, $r : room, $w : weight );
                $ps : PatientStay(admission == $a, bed.room == $r);
        then
                insertLogical(new IntConstraintOccurrence("hasPreferredRoomProperties",ConstraintType.NEGATIVE_SOFT,20*$w,$ps));
end

rule "meetsRoomPreference"
        when
                $mr : MeetsRoomPreferenceConstraint($a : admission, $r : room);
                $ps : PatientStay(admission == $a, bed.room == $r);
        then
                insertLogical(new IntConstraintOccurrence("meetsRoomPreference",ConstraintType.NEGATIVE_SOFT,8,$ps));
end

rule "inGoodDepartment"
        when
                $gd : GoodDepartmentConstraint($a : admission, $d : department);
                $ps : PatientStay(admission == $a, $b : bed, eval($b.getRoom().getDepartment().equals($d)));
        then
                insertLogical(new IntConstraintOccurrence("inGoodDepartment",ConstraintType.NEGATIVE_SOFT,10,$ps));
end

rule "inGoodRoom"
        when
                $gr : GoodRoomConstraint($a : admission, $r : room, $w : weight);
                $ps : PatientStay(admission == $a, bed.room == $r);
        then
                insertLogical(new IntConstraintOccurrence("inGoodRoom",ConstraintType.NEGATIVE_SOFT,10*$w,$ps));               
end

rule "calcScore"
salience -10
        when
                $count : Number() from accumulate( IntConstraintOccurrence($w : weight) ,
                                                                                 sum($w) );
        then
                scoreCalculator.setScore(-$count.doubleValue());
end

The classes with **Constraint in it are possible combinations that cause a constraint to be violated, and are calculated and inserted at initialization time (and are never changed). I know that the rule "patientsToBeAssignedToRoomsOfAppropriateSex" is fairly complex, but even when I remove it, the performance is not fantastic. Is there anything else I can do to get better performance? I'm already using JDK 1.6 and -server mode. Furthermore, all classes used here have their default equals and hashCode methods, so they don't have an impact on performance.

Sincerely,

Wim Vancroonenburg
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