001 package net.sf.cpsolver.studentsct.constraint;
002
003 import java.util.Enumeration;
004 import java.util.Set;
005
006 import net.sf.cpsolver.ifs.model.Constraint;
007 import net.sf.cpsolver.ifs.model.Value;
008 import net.sf.cpsolver.studentsct.model.Enrollment;
009 import net.sf.cpsolver.studentsct.model.Request;
010
011 /**
012 * This constraints ensures that a student is not enrolled into sections that are
013 * overlapping in time.
014 *
015 * <br><br>
016 *
017 * @version
018 * StudentSct 1.1 (Student Sectioning)<br>
019 * Copyright (C) 2007 Tomáš Müller<br>
020 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
021 * Lazenska 391, 76314 Zlin, Czech Republic<br>
022 * <br>
023 * This library is free software; you can redistribute it and/or
024 * modify it under the terms of the GNU Lesser General Public
025 * License as published by the Free Software Foundation; either
026 * version 2.1 of the License, or (at your option) any later version.
027 * <br><br>
028 * This library is distributed in the hope that it will be useful,
029 * but WITHOUT ANY WARRANTY; without even the implied warranty of
030 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
031 * Lesser General Public License for more details.
032 * <br><br>
033 * You should have received a copy of the GNU Lesser General Public
034 * License along with this library; if not, write to the Free Software
035 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
036 */
037 public class StudentConflict extends Constraint {
038
039 /**
040 * A given enrollment is conflicting when the student is enrolled into
041 * another course / free time request that has an assignment that is
042 * overlapping with one or more assignments of the given section.
043 * See {@link Enrollment#isOverlapping(Enrollment)} for more details.
044 * All such overlapping enrollments are added into the provided set of conflicts.
045 * @param value {@link Enrollment} that is being considered
046 * @param conflicts resultant list of conflicting enrollments
047 */
048 public void computeConflicts(Value value, Set conflicts) {
049 //get enrollment
050 Enrollment enrollment = (Enrollment)value;
051
052 //for all assigned course requests -> if overlapping with this enrollment -> conflict
053 for (Enumeration e=assignedVariables().elements();e.hasMoreElements();) {
054 Request request = (Request)e.nextElement();
055 if (request.equals(enrollment.getRequest())) continue;
056 if (enrollment.isOverlapping((Enrollment)request.getAssignment()))
057 conflicts.add(request.getAssignment());
058 }
059
060 //if this enrollment cannot be assigned (student already has a full schedule) -> unassignd a lowest priority request
061 if (!enrollment.getStudent().canAssign(enrollment.getRequest())) {
062 Enrollment lowestPriorityEnrollment = null;
063 int lowestPriority = -1;
064 for (Enumeration e=assignedVariables().elements();e.hasMoreElements();) {
065 Request request = (Request)e.nextElement();
066 if (request.equals(enrollment.getRequest())) continue;
067 if (lowestPriority<request.getPriority()) {
068 lowestPriority = request.getPriority();
069 lowestPriorityEnrollment = (Enrollment)request.getAssignment();
070 }
071 }
072 if (lowestPriorityEnrollment!=null)
073 conflicts.add(lowestPriorityEnrollment);
074 }
075 }
076
077 /** Two enrollments are consistent if they are not overlapping in time */
078 public boolean isConsistent(Value value1, Value value2) {
079 Enrollment e1 = (Enrollment)value1;
080 Enrollment e2 = (Enrollment)value2;
081 return !e1.isOverlapping(e2);
082 }
083
084 /**
085 * A given enrollment is conflicting when the student is enrolled into
086 * another course / free time request that has an assignment that is
087 * overlapping with one or more assignments of the given section.
088 * See {@link Enrollment#isOverlapping(Enrollment)} for more details.
089 * @param value {@link Enrollment} that is being considered
090 * @return true, if the student is enrolled into another enrollment of a
091 * different request that is overlapping in time with the given enrollment
092 */
093 public boolean inConflict(Value value) {
094 //get enrollment
095 Enrollment enrollment = (Enrollment)value;
096
097 //for all assigned course requests -> if overlapping with this enrollment -> conflict
098 for (Enumeration e=assignedVariables().elements();e.hasMoreElements();) {
099 Request request = (Request)e.nextElement();
100 if (request.equals(enrollment.getRequest())) continue;
101 if (enrollment.isOverlapping((Enrollment)request.getAssignment()))
102 return true;
103 }
104
105 //if this enrollment cannot be assigned (student already has a full schedule) -> conflict
106 if (!enrollment.getStudent().canAssign(enrollment.getRequest()))
107 return true;
108
109 //nothing above -> no conflict
110 return false;
111 }
112
113 public String toString() {
114 return "StudentConflicts";
115 }
116 }