Gather the domain objects in a planning solution
A TimeTable
wraps all Timeslot
, Room
, and Lesson
instances of a single dataset.
Furthermore, because it contains all lessons, each with a specific planning variable state,
it is a planning solution and it has a score:
-
If lessons are still unassigned, then it is an uninitialized solution, for example, a solution with the score
-4init/0hard/0soft
. -
If it breaks hard constraints, then it is an infeasible solution, for example, a solution with the score
-2hard/-3soft
. -
If it adheres to all hard constraints, then it is a feasible solution, for example, a solution with the score
0hard/-7soft
.
Create the src/main/java/org/acme/schooltimetabling/domain/TimeTable.java
class:
package org.acme.schooltimetabling.domain;
import java.util.List;
import ai.timefold.solver.core.api.domain.solution.PlanningEntityCollectionProperty;
import ai.timefold.solver.core.api.domain.solution.PlanningScore;
import ai.timefold.solver.core.api.domain.solution.PlanningSolution;
import ai.timefold.solver.core.api.domain.solution.ProblemFactCollectionProperty;
import ai.timefold.solver.core.api.domain.valuerange.ValueRangeProvider;
import ai.timefold.solver.core.api.score.buildin.hardsoft.HardSoftScore;
@PlanningSolution
public class TimeTable {
@ValueRangeProvider
@ProblemFactCollectionProperty
private List<Timeslot> timeslotList;
@ValueRangeProvider
@ProblemFactCollectionProperty
private List<Room> roomList;
@PlanningEntityCollectionProperty
private List<Lesson> lessonList;
@PlanningScore
private HardSoftScore score;
public TimeTable() {
}
public TimeTable(List<Timeslot> timeslotList, List<Room> roomList, List<Lesson> lessonList) {
this.timeslotList = timeslotList;
this.roomList = roomList;
this.lessonList = lessonList;
}
public List<Timeslot> getTimeslotList() {
return timeslotList;
}
public List<Room> getRoomList() {
return roomList;
}
public List<Lesson> getLessonList() {
return lessonList;
}
public HardSoftScore getScore() {
return score;
}
}
The TimeTable
class has an @PlanningSolution
annotation,
so Timefold knows that this class contains all of the input and output data.
Specifically, this class is the input of the problem:
-
A
timeslotList
field with all time slots-
This is a list of problem facts, because they do not change during solving.
-
-
A
roomList
field with all rooms-
This is a list of problem facts, because they do not change during solving.
-
-
A
lessonList
field with all lessons-
This is a list of planning entities, because they change during solving.
-
Of each
Lesson
:-
The values of the
timeslot
androom
fields are typically stillnull
, so unassigned. They are planning variables. -
The other fields, such as
subject
,teacher
andstudentGroup
, are filled in. These fields are problem properties.
-
-
However, this class is also the output of the solution:
-
A
lessonList
field for which eachLesson
instance has non-nulltimeslot
androom
fields after solving -
A
score
field that represents the quality of the output solution, for example,0hard/-5soft
The value range providers
The timeslotList
field is a value range provider.
It holds the Timeslot
instances which Timefold can pick from to assign to the timeslot
field of Lesson
instances.
The timeslotList
field has an @ValueRangeProvider
annotation to connect the @PlanningVariable
with the @ValueRangeProvider
,
by matching the type of the planning variable with the type returned by the value range provider.
Following the same logic, the roomList
field also has an @ValueRangeProvider
annotation.
The problem fact and planning entity properties
Furthermore, Timefold needs to know which Lesson
instances it can change
as well as how to retrieve the Timeslot
and Room
instances used for score calculation
by your TimeTableConstraintProvider
.
The timeslotList
and roomList
fields have an @ProblemFactCollectionProperty
annotation,
so your TimeTableConstraintProvider
can select from those instances.
The lessonList
has an @PlanningEntityCollectionProperty
annotation,
so Timefold can change them during solving
and your TimeTableConstraintProvider
can select from those too.