由于 jMetal 不是一种专门用于排课的程序库,因此本文将提供一个简单的示例,用于说明如何使用 jMetal 求解排课问题。

假设我们要为一个学校制定一个课程表。我们有一些老师和一些班级。每个老师都有自己的课程,每个班级需要上不同的课程。我们必须确保每个老师在每个时间段只有一个课程,每个班级在每个时间段只上一个课程。

我们将使用 jMetal 中的遗传算法来解决这个问题。我们需要定义基因型和适应度函数,然后运行算法。

首先,我们需要定义基因型。在此示例中,我们将使用一个二维数组来表示课程表。第一维表示时间,第二维表示课程。每个单元格将包含一个课程和一个老师。我们将使用整数来表示老师和课程,这些整数将在其他地方定义。

public class Schedule {
    private int[][] schedule;

    public Schedule(int numTimeSlots, int numCourses) {
        schedule = new int[numTimeSlots][numCourses];
    }

    public void setCourse(int timeSlot, int course, int teacher) {
        schedule[timeSlot][course] = teacher;
    }

    public int getCourse(int timeSlot, int course) {
        return schedule[timeSlot][course];
    }

    public Schedule copy() {
        Schedule copy = new Schedule(schedule.length, schedule[0].length);
        for (int i = 0; i < schedule.length; i++) {
            for (int j = 0; j < schedule[i].length; j++) {
                copy.setCourse(i, j, schedule[i][j]);
            }
        }
        return copy;
    }
}

接下来,我们需要定义适应度函数。适应度函数将计算课程表的质量,并将其转换为适应度分数。在此示例中,我们将使用以下规则来计算适应度:

  • 每个老师在每个时间段只能上一门课程。如果一个老师在一个时间段上了两门课,适应度将减少 1 分。
  • 每个班级在每个时间段只能上一门课程。如果一个班级在一个时间段上了两门课,适应度将减少 1 分。
  • 每个老师的所有课程都应该在课程表中出现。如果一个老师的某些课程没有出现在课程表中,适应度将减少 1 分。
  • 每个班级的所有课程都应该在课程表中出现。如果一个班级的某些课程没有出现在课程表中,适应度将减少 1 分。
public class ScheduleFitness implements Fitness<Schedule> {
    private int[][] teacherCounts;
    private int[][] courseCounts;
    private int numTeachers;
    private int numCourses;
    private int numTimeSlots;

    public ScheduleFitness(int[][] teacherCounts, int[][] courseCounts) {
        this.teacherCounts = teacherCounts;
        this.courseCounts = courseCounts;
        numTeachers = teacherCounts.length;
        numCourses = courseCounts[0].length;
        numTimeSlots = courseCounts.length;
    }

    @Override
    public double evaluate(Schedule solution) {
        int numConflicts = 0;
        int numTeacherConflicts = 0;
        int numCourseConflicts = 0;
        int numMissingTeachers = 0;
        int numMissingCourses = 0;

        // 初始化两个计数器,用于计算老师和班级在每个时间段上的课程数
        int[][] teacherCountsCopy = new int[numTeachers][numTimeSlots];
        int[][] courseCountsCopy = new int[numTimeSlots][numCourses];
        for (int i = 0; i < numTeachers; i++) {
            for (int j = 0; j < numTimeSlots; j++) {
                teacherCountsCopy[i][j] = teacherCounts[i][j];
            }
        }
        for (int i = 0; i < numTimeSlots; i++) {
            for (int j = 0; j < numCourses; j++) {
                courseCountsCopy[i][j] = courseCounts[i][j];
            }
        }

        // 遍历课程表,计算冲突和缺失的老师和课程
        for (int i = 0; i < numTimeSlots; i++) {
            for (int j = 0; j < numCourses; j++) {
                int teacher = solution.getCourse(i, j);
                int course = j;

                // 检查老师是否在该时间段上了两门课
                if (teacherCountsCopy[teacher][i] > 0) {
                    numTeacherConflicts++;
                }
                teacherCountsCopy[teacher][i]++;

                // 检查班级是否在该时间段上了两门课
                if (courseCountsCopy[i][course] > 0) {
                    numCourseConflicts++;
                }
                courseCountsCopy[i][course]++;

                // 检查老师和课程是否都在课程表中出现
                if (teacherCounts[teacher][i] == 0) {
                    numMissingTeachers++;
                }
                if (courseCounts[i][course] == 0) {
                    numMissingCourses++;
                }
            }
        }

        // 计算适应度分数
        numConflicts = numTeacherConflicts + numCourseConflicts;
        double fitness = 1.0 / (1.0 + numConflicts + numMissingTeachers + numMissingCourses);
        return fitness;
    }
}

现在我们已经定义了基因型和适应度函数,我们可以使用 jMetal 进行排课。以下是完整的代码示例:

public class ScheduleProblem extends GenericProblem<Schedule> {
    private int[][] teacherCounts;
    private int[][] courseCounts;
    private int numTeachers;
    private int numCourses;
    private int numTimeSlots;

    public ScheduleProblem(int[][] teacherCounts, int[][] courseCounts, int numTimeSlots, int numCourses) {
        this.teacherCounts = teacherCounts;
        this.courseCounts = courseCounts;
        this.numTeachers = teacherCounts.length;
        this.numCourses = courseCounts[0].length;
        this.numTimeSlots = numTimeSlots;
    }

    @Override
    public void evaluate(Schedule solution) {
        Fitness<Schedule> fitness = getFitness();
        solution.setFitness(fitness.evaluate(solution));
    }

    @Override
    public Fitness<Schedule> getFitness() {
        return new ScheduleFitness(teacherCounts, courseCounts);
    }

    @Override
    public Solution<Schedule> createSolution() {
        Schedule schedule = new Schedule(numTimeSlots, numCourses);
        for (int i = 0; i < numTimeSlots; i++) {
            for (int j = 0; j < numCourses; j++) {
                int teacher = ThreadLocalRandom.current().nextInt(numTeachers);
                schedule.setCourse(i, j, teacher);
            }
        }
        Solution<Schedule> solution = new Solution<>(schedule);
        evaluate(solution.getVariable());
        return solution;
    }

    public static void main(String[] args) {
        int[][] teacherCounts = {{1, 1, 1, 1, 1}, {1, 1, 1, 1, 1}, {1, 1, 1, 1, 1}};
        int[][] courseCounts = {{1, 1, 1, 1}, {1, 1, 1, 1}, {1, 1, 1, 1}, {1, 1, 1, 1}, {1, 1, 1, 1}};
        int numTimeSlots = 5;
        int numCourses = 4;
        int populationSize = 100;
        int maxEvaluations = 1000;

        Problem<Schedule> problem = new ScheduleProblem(teacherCounts, courseCounts, numTimeSlots, numCourses);
        Algorithm<List<Solution<Schedule>>> algorithm = new GeneticAlgorithm<>(problem, populationSize, maxEvaluations);
        algorithm.run();
        List<Solution<Schedule>> solutions = algorithm.getResult();

        for (Solution<Schedule> solution : solutions) {
            Schedule schedule = solution.getVariable();
            System.out.println("Fitness: " + solution.getFitness());
            for (int i = 0; i < numTimeSlots; i++) {
                for (int j = 0; j < numCourses; j++) {
                    int teacher = schedule.getCourse(i, j);
                    System.out.print("T" + teacher + "C" + j + " ");
                }
                System.out.println();
            }
            System.out.println();
        }
    }
}

在此示例中,我们使用了一个三个老师和五个班级的简单示例。每个老师和每个班级都需要在每个时间段上一个课程。我们使用 GeneticAlgorithm 类运行遗传算法,指定种群大小和最大评估次数。最后,我们打印出每个解决方案的适应度分数和课程表。


原文地址: https://www.cveoy.top/t/topic/uTB 著作权归作者所有。请勿转载和采集!

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