optaplanner can't get the best solution, and different input orders produce different solutions - optaplanner

Question

I'm trying to make a demo using optaplanner: there are some schemes, each scheme has attribute of gain and cost, and a scheme may conflict with one or more other schemes. The question is to find out a group of schemes which match following constraints:
hard constraint: selected schemea may not conflict with each other in this group
soft constraint: make the difference between total gain and total cost as high as possible
I built following code and try to resolve the question:
#PlanningEntity
#Data
#NoArgsConstructor
public class Scheme {
#PlanningId
private String id;
private int gain;
private int cost;
#PlanningVariable(valueRangeProviderRefs = {"validRange"})
// when valid is ture means this scheme will be selected into the solution group
private Boolean valid;
private Set<String> conflicts = new HashSet<>();
public void addConflict(String id) {
conflicts.add(id);
}
public Scheme(String id, int gain, int cost, String[] conflicts) {
this.id = id;
this.gain = gain;
this.cost = cost;
for (String s : conflicts) {
addConflict(s);
}
}
}
#PlanningSolution
public class SchemeSolution {
private HardSoftScore score;
private List<Scheme> schemeList;
#ProblemFactCollectionProperty
#ValueRangeProvider(id = "validRange")
public List<Boolean> getValidRange() {
return Arrays.asList(Boolean.FALSE, Boolean.TRUE);
}
#PlanningScore
public HardSoftScore getScore() {
return score;
}
public void setScore(HardSoftScore score) {
this.score = score;
}
#PlanningEntityCollectionProperty
public List<Scheme> getSchemeList() {
return schemeList;
}
public void setSchemeList(List<Scheme> schemeList) {
this.schemeList = schemeList;
}
}
And the constraint rule as below:
rule "conflictCheck"
when
Boolean(this==true) from accumulate (
$schs: List() from collect (Scheme(valid==true)),
init(boolean cfl = false;Set cfSet = new HashSet();List ids = new ArrayList()),
action(
for(int i = 0; i < $schs.size(); ++i) {
Scheme sch = (Scheme)$schs.get(i);
cfSet.addAll(sch.getConflicts());
ids.add(sch.getId());
}
for( int i = 0; i < ids.size(); ++i) {
String id = (String)ids.get(i);
if(cfSet.contains(id)) {
cfl = true;
return true;
}
}
),
result(cfl)
)
then
scoreHolder.addHardConstraintMatch(kcontext, -10000);
end
rule "bestGain"
when
$gc : Number() from
accumulate(
Scheme(valid==true, $gain : gain, $cost: cost),
sum($gain - $cost)
)
then
scoreHolder.addSoftConstraintMatch(kcontext, $gc.intValue());
end
Then I constructed three schemes as input of the test. Oddly, I found that optaplanner can't get the best solution, and different input orders produce different solutions.
When I set input as following:
private static List<Scheme> getSchemes() {
List<Scheme> ret = new ArrayList();
ret.add(new Scheme("S1", 5, 2, new String[]{"S3"}));
ret.add(new Scheme("S2", 3, 1, new String[]{"S3"}));
ret.add(new Scheme("S3", 10, 4, new String[]{"S1", "S2"}));
return ret;
}
the output is :
0hard/5soft
Scheme(id=S1, gain=5, cost=2, valid=true, conflicts=[S3])
Scheme(id=S2, gain=3, cost=1, valid=true, conflicts=[S3])
Scheme(id=S3, gain=10, cost=4, valid=false, conflicts=[S1, S2])
And when I set input as following:
private static List<Scheme> getSchemes() {
List<Scheme> ret = new ArrayList();
ret.add(new Scheme("S3", 10, 4, new String[]{"S1", "S2"}));
ret.add(new Scheme("S1", 5, 2, new String[]{"S3"}));
ret.add(new Scheme("S2", 3, 1, new String[]{"S3"}));
return ret;
}
I get the best solution and the output is :
0hard/6soft
Scheme(id=S3, gain=10, cost=4, valid=true, conflicts=[S1, S2])
Scheme(id=S1, gain=5, cost=2, valid=false, conflicts=[S3])
Scheme(id=S2, gain=3, cost=1, valid=false, conflicts=[S3])
Could anyone help me about it?