001 package net.sf.cpsolver.studentsct.constraint;
002
003 import java.util.Set;
004
005 import net.sf.cpsolver.ifs.model.Constraint;
006 import net.sf.cpsolver.studentsct.model.Enrollment;
007 import net.sf.cpsolver.studentsct.model.Request;
008 import net.sf.cpsolver.studentsct.model.Student;
009
010 /**
011 * This constraints ensures that a student is not enrolled into sections that
012 * are overlapping in time.
013 *
014 * <br>
015 * <br>
016 *
017 * @version StudentSct 1.2 (Student Sectioning)<br>
018 * Copyright (C) 2007 - 2010 Tomas Muller<br>
019 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
020 * <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
021 * <br>
022 * This library is free software; you can redistribute it and/or modify
023 * it under the terms of the GNU Lesser General Public License as
024 * published by the Free Software Foundation; either version 3 of the
025 * License, or (at your option) any later version. <br>
026 * <br>
027 * This library is distributed in the hope that it will be useful, but
028 * WITHOUT ANY WARRANTY; without even the implied warranty of
029 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
030 * Lesser General Public License for more details. <br>
031 * <br>
032 * You should have received a copy of the GNU Lesser General Public
033 * License along with this library; if not see
034 * <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
035 */
036 public class StudentConflict extends Constraint<Request, Enrollment> {
037
038 /**
039 * Constructor
040 * @param student student for which the constraint is created
041 */
042 public StudentConflict(Student student) {
043 super();
044 for (Request request : student.getRequests())
045 addVariable(request);
046 }
047
048 /**
049 * A given enrollment is conflicting when the student is enrolled into
050 * another course / free time request that has an assignment that is
051 * overlapping with one or more assignments of the given section. See
052 * {@link Enrollment#isOverlapping(Enrollment)} for more details. All such
053 * overlapping enrollments are added into the provided set of conflicts.
054 *
055 * @param enrollment
056 * {@link Enrollment} that is being considered
057 * @param conflicts
058 * resultant list of conflicting enrollments
059 */
060 @Override
061 public void computeConflicts(Enrollment enrollment, Set<Enrollment> conflicts) {
062 // for all assigned course requests -> if overlapping with this
063 // enrollment -> conflict
064 for (Request request : assignedVariables()) {
065 if (request.equals(enrollment.getRequest()))
066 continue;
067 if (enrollment.isOverlapping(request.getAssignment()))
068 conflicts.add(request.getAssignment());
069 }
070
071 // if this enrollment cannot be assigned (student already has a full
072 // schedule) -> unassignd a lowest priority request
073 if (!enrollment.getAssignments().isEmpty() && !enrollment.getStudent().canAssign(enrollment.getRequest())) {
074 Enrollment lowestPriorityEnrollment = null;
075 int lowestPriority = -1;
076 for (Request request : assignedVariables()) {
077 if (request.equals(enrollment.getRequest()))
078 continue;
079 if (lowestPriority < request.getPriority()) {
080 lowestPriority = request.getPriority();
081 lowestPriorityEnrollment = request.getAssignment();
082 }
083 }
084 if (lowestPriorityEnrollment != null)
085 conflicts.add(lowestPriorityEnrollment);
086 }
087 }
088
089 /** Two enrollments are consistent if they are not overlapping in time */
090 @Override
091 public boolean isConsistent(Enrollment e1, Enrollment e2) {
092 return !e1.isOverlapping(e2);
093 }
094
095 /**
096 * A given enrollment is conflicting when the student is enrolled into
097 * another course / free time request that has an assignment that is
098 * overlapping with one or more assignments of the given section. See
099 * {@link Enrollment#isOverlapping(Enrollment)} for more details.
100 *
101 * @param enrollment
102 * {@link Enrollment} that is being considered
103 * @return true, if the student is enrolled into another enrollment of a
104 * different request that is overlapping in time with the given
105 * enrollment
106 */
107 @Override
108 public boolean inConflict(Enrollment enrollment) {
109 // for all assigned course requests -> if overlapping with this
110 // enrollment -> conflict
111 for (Request request : assignedVariables()) {
112 if (request.equals(enrollment.getRequest()))
113 continue;
114 if (enrollment.isOverlapping(request.getAssignment()))
115 return true;
116 }
117
118 // if this enrollment cannot be assigned (student already has a full
119 // schedule) -> conflict
120 if (!enrollment.getStudent().canAssign(enrollment.getRequest()))
121 return true;
122
123 // nothing above -> no conflict
124 return false;
125 }
126
127 @Override
128 public String toString() {
129 return "StudentConflicts";
130 }
131 }