转载自：Destroy和Repair方法代码实现解析

在整一个ALNS框架中呢，涉及这俩的有：

Destroy和Repair方法的具体实现、Destroy和Repair方法管理（包括各个Destroy和Repair方法权重分配、成绩打分、按权重选择哪个Destroy和Repair方法等操作）。

• Destroy和Repair方法具体实现模块

• Destroy和Repair方法管理模块

一、Destroy和Repair方法具体实现

关于Destroy和Repair方法，由三个类组成，分别是AOperator、ADestroyOperator、ARepairOperator。它们之间的继承派生关系如下：

1.1  AOperator

这是一个基础父类，它抽象了Destroy和Repair方法共有的一些方法和特征（成绩、权重、名称等等），然后Destroy和Repair方法再各自继承于它，实现自己的功能模块。

成员变量已经注释清楚了，关于protected的一个成员noise噪声模式会在后面讲到。

  1class AOperator
  2{
  3private:
  4    //! Total number of calls during the process.
  5    size_t totalNumberOfCalls;
  6
  7    //! Number of calls since the last evaluation.
  8    size_t nbCallsSinceLastEval;
  9
 10    //! score of the operator.
 11    double score;
 12
 13    //! weight of the operator.
 14    double weight;
 15
 16    //! designation of the operator.
 17    std::string operatorName;
 18
 19protected:
 20    //! Indicate if the operator is used in noise mode or not.
 21    bool noise;
 22public:
 23
 24    //! Constructor.
 25    AOperator(std::string name){
 26        operatorName = name;
 27        init();
 28    }
 29
 30    //! Destructor.
 31    virtual ~AOperator(){};
 32
 33    //! Initialize the values of the numbers of calls.
 34    void init()
 35    {
 36        totalNumberOfCalls = 0;
 37        nbCallsSinceLastEval = 0;
 38        score = 0;
 39        weight = 1;
 40    }
 41
 42    //! reset the number of calls since last eval.
 43    void resetNumberOfCalls()
 44    {
 45        nbCallsSinceLastEval = 0;
 46    }
 47
 48    //! Simple getter.
 49    //! \return the total number of calls to the operator since
 50    //! the beginning of the optimization process.
 51    size_t getTotalNumberOfCalls(){return totalNumberOfCalls;};
 52
 53    //! Simple getter.
 54    //! \return the number of calls to this operator since the last
 55    //! evaluation.
 56    size_t getNumberOfCallsSinceLastEvaluation(){return nbCallsSinceLastEval;};
 57
 58    void increaseNumberOfCalls()
 59    {
 60        totalNumberOfCalls++;
 61        nbCallsSinceLastEval++;
 62    }
 63
 64    //! Simple getter.
 65    double getScore() const
 66    {
 67        return score;
 68    }
 69
 70    //! Simple getter.
 71    double getWeight() const
 72    {
 73        return weight;
 74    }
 75
 76    //! resetter.
 77    void resetScore()
 78    {
 79        this->score = 0;
 80    }
 81
 82    //! Simple setter.
 83    void setScore(double s)
 84    {
 85        this->score = s;
 86    }
 87
 88    //! Simple setter.
 89    void setWeight(double weight)
 90    {
 91        this->weight = weight;
 92    }
 93
 94    //! Simple getter.
 95    std::string getName(){return operatorName;};
 96
 97    //! Set noise to true.
 98    void setNoise(){noise=true;};
 99
100    //! Set noise to false.
101    void unsetNoise(){noise=false;};
102
103};

1.2 ADestroyOperator

该类主要是继承于上面的AOperator类，然后再此基础上加上Destroy操作的具体实现。它是一个抽象类，需要在后续的应用中重写Destroy操作的方法。

 1class ADestroyOperator : public AOperator {
 2protected:
 3    //! The minimum destroy size used.
 4    size_t minimunDestroy;
 5    //! The maximum destroy size used.
 6    size_t maximumDestroy;
 7
 8public:
 9    //! Constructor.
10    //! \param mini the minimum destroy size.
11    //! \param maxi the maximum destroy size.
12    //! \param s the name of the destroy operator.
13    ADestroyOperator(size_t mini, size_t maxi, std::string s) : AOperator(s)
14    {
15        minimunDestroy = mini;
16        maximumDestroy = maxi;
17    }
18
19    //! Destructor.
20    virtual ~ADestroyOperator(){};
21
22    //! This function is the one called to destroy a solution.
23    //! \param sol the solution to be destroyed.
24    virtual void destroySolution(ISolution& sol)=0;
25};

1.3 ARepairOperator

同理这个类也是一个抽象类，需要在后续的使用中重写Repair方法。

 1class ARepairOperator : public AOperator {
 2
 3public:
 4    ARepairOperator(std::string s) : AOperator(s)
 5    {
 6    }
 7
 8    virtual ~ARepairOperator(){};
 9
10    virtual void repairSolution(ISolution& sol)=0;
11};

二、Destroy和Repair方法管理

对Destroy和Repair方法进行管理的由两个类来实现：AOperatorManager、OperatorManager

其中AOperatorManager是抽象类，只提供接口，OperatorManager 继承 AOperatorManager。并对其接口进行实现。

2.1  AOperatorManager

该类抽象了OperatorManager的一些特征，只提供接口。因此成员函数都是纯虚函数。。

关于保护成员：stats用于保存算法迭代过程中的一些状态量，这个类后续也会讲解的。

 1class AOperatorManager
 2{
 3public:
 4    //! This method selects a destroy operator.
 5    //! \return a destroy operator.
 6    virtual ADestroyOperator& selectDestroyOperator()=0;
 7
 8    //! This method selects a repair operator.
 9    //! \return a repair operator.
10    virtual ARepairOperator& selectRepairOperator()=0;
11
12    virtual void recomputeWeights()=0;
13
14    //! Update the scores of the operators.
15    virtual void updateScores(ADestroyOperator& des, ARepairOperator& rep, ALNS_Iteration_Status& status)=0;
16
17    //! Indicate that the optimization process starts.
18    virtual void startSignal()=0;
19
20    //! Destroy the operators registered to this operator manager.
21    virtual void end()=0;
22
23    //! Simple setter.
24    void setStatistics(Statistics* statistics){stats = statistics;};
25protected:
26    //! A pointer to the instance of the statistics module.
27    Statistics* stats;
28};

2.2 OperatorManager

该类在AOperatorManager基础上也添加了一些自己额外的成员变量和函数方法

 1class OperatorManager: public AOperatorManager {
 2private:
 3    //! The set of repair operators.
 4    std::vector<AOperator*> repairOperators;
 5
 6    //! The set of destroy operators.
 7    std::vector<AOperator*> destroyOperators;
 8
 9    //! The sum of the weights of the repair operators.
10    double sumWeightsRepair;
11
12    //! The sum of the weights of the destroy operators.
13    double sumWeightsDestroy;
14
15    //! The paramaters to be used by the ALNS.
16    ALNS_Parameters* parameters;
17
18    //! Indicate whether or not the next operators to be return
19    //! should be noised or not.
20    bool noise;
21
22    //! A counter that indicates the number of times repair operators with noise have been successfull
23    double performanceRepairOperatorsWithNoise;
24    //! A counter that indicates the number of times repair operators without noise have been successfull
25    double performanceRepairOperatorsWithoutNoise;
26
27
28    //! Use a roulette wheel to select an operator in a vector of operators.
29    //! \return the selected operator.
30    AOperator& selectOperator(std::vector<AOperator*>& vecOp, double sumW);
31
32    //! Recompute the weight of an operator.
33    void recomputeWeight(AOperator& op, double& sumW);
34public:
35    //! Constructor
36    //! \param param the parameters to be used.
37    OperatorManager(ALNS_Parameters& param);
38
39    //! Destructor.
40    virtual ~OperatorManager();
41
42    //! This function recompute the weights of every operator managed by this
43    //! manager.
44    void recomputeWeights();
45
46    //! This method selects a destroy operator.
47    //! \return a destroy operator.
48    ADestroyOperator& selectDestroyOperator();
49
50    //! This method selects a repair operator.
51    //! \return a repair operator.
52    ARepairOperator& selectRepairOperator();
53
54    //! This method adds a repair operator to the list
55    //! of repair operator managed by this manager.
56    //! \param repairOperator the repair operator to be added.
57    void addRepairOperator(ARepairOperator& repairOperator);
58
59    //! This method adds a destroy operator to the list
60    //! of destroy operator managed by this manager.
61    //! \param destroyOperator the destroy operator to be added.
62    void addDestroyOperator(ADestroyOperator& destroyOperator);
63
64    //! This method run some sanity checks to ensure that it is possible
65    //! to "safely" use this manager within the ALNS.
66    void sanityChecks();
67
68    //! Update the scores of the operators.
69    virtual void updateScores(ADestroyOperator& des, ARepairOperator& rep, ALNS_Iteration_Status& status);
70
71    //! Indicate that the optimization process starts.
72    virtual void startSignal();
73
74    //! Destroy all the operators registered to this operator.
75    void end();
76};

以上均为该类的.h文件具体实现的重点部分如下

---

三、OperatorManager具体实现

3.1 OperatorManager::recomputeWeight()

重新计算单个操作的权重。其有两个参数AOperator& op, double& sumW。

其中 op是要重新计算权重的repair或者destroy方法，sumW是其对应集合的权重总和。新权重的计算方式：

其中：

Rho为设定的[0, 1]之间的参数。

PrevWeight表示旧的权重。

nbCalls表示在上一次自上一次更新完权重到现在该方法被调用的次数。

timeSegmentsIt表示迭代多少次需要重新计算一下权重的迭代次数。

currentScore表示旧的成绩。

 1void OperatorManager::recomputeWeight(AOperator& op, double& sumW)
 2{
 3    double prevWeight = op.getWeight();
 4    sumW -= prevWeight;
 5    double currentScore = op.getScore();
 6    size_t nbCalls = op.getNumberOfCallsSinceLastEvaluation();
 7    double newWeight = (1-parameters->getRho())*prevWeight + parameters->getRho()*(static_cast<double>(nbCalls)/static_cast<double>(parameters->getTimeSegmentsIt()))*currentScore;
 8    // We ensure that the weight is within the bounds.
 9    if(newWeight > parameters->getMaximumWeight())
10    {
11        newWeight = parameters->getMaximumWeight();
12    }
13    if(newWeight < parameters->getMinimumWeight())
14    {
15        newWeight = parameters->getMinimumWeight();
16    }
17
18    sumW += newWeight;
19    op.setWeight(newWeight);
20    op.resetScore();
21    op.resetNumberOfCalls();
22}

值得注意的是 OperatorManager::recomputeWeights() 成员函数是用于重新计算repair或者destroy方法集合的。

3.2 OperatorManager::selectOperator(...)

当然，并不是说权重大的方法一定会被选中，只是被选中的可能性会大而已。

具体过程是先生成一个在0~sumWeight之间的中间权重randomWeightPos ，然后从第一个方法开始用变量cumulSum进行权重累加，直到cumulSum>=randomWeightPos 为止，那么停止累加时最后这个方法就是幸运儿了。

 1AOperator& OperatorManager::selectOperator(std::vector<AOperator*>& vecOp, double sumW)
 2{
 3    double randomVal = static_cast<double>(rand())/static_cast<double>(RAND_MAX);
 4    double randomWeightPos = randomVal*sumW;
 5    double cumulSum = 0;
 6    for(size_t i = 0; i < vecOp.size(); i++)
 7    {
 8        cumulSum += vecOp[i]->getWeight();
 9        if(cumulSum >= randomWeightPos)
10        {
11            if(noise)
12            {
13                vecOp[i]->setNoise();
14            }
15            else
16            {
17                vecOp[i]->unsetNoise();
18            }
19            vecOp[i]->increaseNumberOfCalls();
20            return *(vecOp[i]);
21        }
22    }
23    assert(false);
24    return *(vecOp.back());
25}

3.3  OperatorManager::updateScores(...)

该成员函数用来更新各个Destroy和Repair方法的成绩。参数是Destroy和Repair方法的集合，以及ALNS迭代过程中的各种状态信息。

便于说明下面用rScore和dScore分别代表Repair和Destroy方法的成绩。具体实现如下：

1) 如果找到新的最优解，rScore+=Sigma1，dScore+=Sigma1。其中Sigma1是设定参数。

2) 如果当前解得到改进，rScore+=Sigma2，dScore+=Sigma2。其中Sigma2是设定参数。

3) 如果当前解没有得到改进 and 当前解是之前没有出现过的 and 当前解被接受作为新的解了，rScore+=Sigma3，dScore+=Sigma3。其中Sigma3是设定参数。

 1void OperatorManager::updateScores(ADestroyOperator& des, ARepairOperator& rep, ALNS_Iteration_Status& status)
 2{
 3    if(status.getNewBestSolution() == ALNS_Iteration_Status::TRUE)
 4    {
 5        rep.setScore(rep.getScore()+parameters->getSigma1());
 6        des.setScore(des.getScore()+parameters->getSigma1());
 7        performanceRepairOperatorsWithNoise += 1;
 8        performanceRepairOperatorsWithoutNoise += 1;
 9    }
10
11    if(status.getImproveCurrentSolution() == ALNS_Iteration_Status::TRUE)
12    {
13        rep.setScore(rep.getScore()+parameters->getSigma2());
14        des.setScore(des.getScore()+parameters->getSigma2());
15        performanceRepairOperatorsWithNoise += 1;
16        performanceRepairOperatorsWithoutNoise += 1;
17    }
18
19    if(status.getImproveCurrentSolution() == ALNS_Iteration_Status::FALSE
20            && status.getAcceptedAsCurrentSolution() == ALNS_Iteration_Status::TRUE
21            && status.getAlreadyKnownSolution() == ALNS_Iteration_Status::FALSE)
22    {
23        rep.setScore(rep.getScore()+parameters->getSigma3());
24        des.setScore(des.getScore()+parameters->getSigma3());
25        performanceRepairOperatorsWithNoise += 1;
26        performanceRepairOperatorsWithoutNoise += 1;
27    }
28    /* OLD VERSION */
29    /*
30    if(parameters->getNoise())
31    {
32        double randNoise = static_cast<double>(rand())/RAND_MAX;
33        noise = (randNoise<parameters->getProbabilityOfNoise());
34    }
35    */
36    /* NEW VERSION */
37
38    if(parameters->getNoise())
39    {
40        double performanceRepairOperatorsGlobal = 0;
41        performanceRepairOperatorsGlobal += performanceRepairOperatorsWithNoise;
42        performanceRepairOperatorsGlobal += performanceRepairOperatorsWithoutNoise;
43
44        double randomVal = static_cast<double>(rand())/RAND_MAX;
45        double randomWeightPos = randomVal*performanceRepairOperatorsGlobal;
46        noise = (randomWeightPos < performanceRepairOperatorsGlobal);
47    }
48}