我正在研究一种算法，除了一件事之外它似乎工作得很好。
让我先向您展示代码，然后我将解释代码的作用以及问题所在。
public Triple<List<ROUTE>, Integer, List<Customer>> LocalSearch()
{
int noImprLS = 0;
boolean initialization = false;
List<ROUTE> bestRoutes = startRoutes;
int bestProfit = profit;
List<Customer> bestU = u;
List<ROUTE> tempBestRoutes = startRoutes;
int tempBestProfit = profit;
List<Customer> tempBestU = u;
int tempBestDistance = totalDistance(tempBestRoutes);
ELIMINATOR e = new ELIMINATOR(bestU, bestRoutes, bestProfit, initialization, name, rnd);
while (noImprLS <= noImprUB)
{
System.out.print(noImprLS);
boolean improvement = false;
long starttime = System.nanoTime();
double timeE = 0;
for (int i = 1; i <= N; i++)
{
long starttimeE = System.nanoTime();
e = new ELIMINATOR(bestU, bestRoutes, bestProfit, initialization, name, rnd);
timeE = timeE + (System.nanoTime()-starttimeE)/1000000000.0;
POSTPROCEDURE pp = new POSTPROCEDURE(e.getRoutes(), profitRoutes(e.getRoutes()), e.getU(), name);
for (int p = 0; p < pp.getBestSolution().size(); p++)
{
ROUTE r = pp.getBestSolution().get(p);
addToPOOL(r);
}
int tempprofit = pp.getTP();
int tempdistance = pp.getTD();
if (tempprofit > tempBestProfit)
{
tempBestRoutes = pp.getBestSolution();
tempBestProfit = tempprofit;
tempBestU = pp.getU();
tempBestDistance = tempdistance;
}
else if (tempprofit == tempBestProfit)
{
if (tempdistance < tempBestDistance)
{
tempBestRoutes = pp.getBestSolution();
tempBestProfit = tempprofit;
tempBestU = pp.getU();
tempBestDistance = tempdistance;
}
}
}
if (tempBestProfit > bestProfit)
{
// Move to better neighbor
bestRoutes = tempBestRoutes;
bestProfit = tempBestProfit;
bestU = tempBestU;
noImprLS = 0;
improvement = true;
System.out.print(" total profit: " + bestProfit);
}
else if (tempBestProfit == bestProfit)
{
if (totalDistance(tempBestRoutes) < totalDistance(bestRoutes))
{
// Move to better neighbor
bestRoutes = tempBestRoutes;
bestProfit = tempBestProfit;
bestU = tempBestU;
noImprLS = 0;
improvement = true;
System.out.print(" total profit: " + bestProfit + " total distance: " + totalDistance(bestRoutes));
}
}
if (improvement == false)
{
noImprLS++;
}
long endtime = System.nanoTime();
double duration = (endtime - starttime)/1000000000.0;
System.out.print(" duration: " + duration + " timeE: " + timeE + "\n");
}
解释 我知道代码很冗长，但这一切都非常重要。在这段代码中，我正在编写一个针对Time Orienteering Problem with Time Windows的算法（广泛的车辆路径问题）。我的目标是找到一套利润最大的好路线。在下面的示例中，bestRoutes和tempBestRoutes由4条不同的路由组成，profit（bestProfit / tempBestProfit）分别等于这些路由的总利润，而（temp）bestU是尚未包含在我的路由中的客户列表。
现在问题在于ELIMINATOR。此方法删除并添加一些客户。此类的输出用于PostProcedure，它也会更改路径中的某些事实。
我希望现在我的代码正在做什么。我正在考虑N个社区，我会选择最好的一个。如果最好的一个并不比我的起始解决方案好，那么我将noImprLS增加一个。我继续考虑新的nieghbours，直到我的上限连续迭代次数没有改善。
问题 现在的问题是，如果我没有找到更好的解决方案，因此我继续在ELIMINATOR中插入相同的路线和利润，我的计算时间也会增加。
一些示例，其中duration表示while循环中迭代的时间，timeE表示for循环中ELIMINATOR的总时间是多少。很明显，ELIMINATOR会导致持续时间增加。
0总利润：800持续时间：0.486570471 timeE：0.16644330999999998
0总利润：900持续时间：0.431213528时间：0.11342619799999998
0总利润：950持续时间：0.444671005 timeE：0.12090608200000001
0总利润：960期限：0.519406695时间：0.16836757300000005
0持续时间：0.460473438 timeE：0.137813155
1持续时间：0.572109775 timeE：0.30774360900000003
2持续时间：0.698965292 timeE：0.471859029
3持续时间：0.918376211 timeE：0.686916669
4持续时间：1.165481175 timeE：0.92621492
5持续时间：1.326080436 timeE：1.0874366910000002
6持续时间：2.006102605 timeE：1.674879135
7持续时间：2.787172112 timeE：2.4276636639999993
8持续时间：2.042213493 timeE：1.7967797849999998
9持续时间：2.652985618 timeE：2.3503671230000003
10持续时间：2.422183993 timeE：2.1859969810000006
消除器代码：
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Random;
public class ELIMINATOR extends BASIS
{
private List<Customer> u;
private List<ROUTE> routes;
private int totalprofit;
private Random prob;
public ELIMINATOR(List<Customer> u, List<ROUTE> routes, int profit, boolean initialization, String name, Random rnd)
{
super(name);
this.u = u;
this.routes = routes;
this.totalprofit = profit;
this.prob = rnd;
if (initialization == true)
{
addCustomers();
for (ROUTE route : routes)
{
checkCorrectNess(route, "after adding procedure in eliminator");
}
}
else
{
removeCustomers();
for (ROUTE route : routes)
{
checkCorrectNess(route, "after removing procedure in eliminator");
}
addCustomers();
for (ROUTE route : routes)
{
checkCorrectNess(route, "after removing and adding procedure in eliminator");
}
}
}
public void removeCustomers()
{
double Ph = 0.1;
double Pl = 0.3;
double total_profit = totalprofit;
int num_customers = 0;
// Calculate the total profit and total number of customers in the routes
for(ROUTE route : routes)
{
num_customers = num_customers + (route.getLocations().size()-2);
}
// Calculate average profit
double average_profit = total_profit/num_customers;
// For each customer on each route, determine whether he/she will be removed
for(ROUTE r : routes)
{
List<RouteNode> route = r.getLocations();
int routesize = route.size();
int j = 1;
while (j < routesize-1)
{
boolean removed = false;
RouteNode node = route.get(j);
if (node.customer.getProfit() >= average_profit)
{
if (prob.nextDouble() < Ph)
{
removed = true;
RouteNode node_toberemoved = node;
int index_node = route.indexOf(node);
route.remove(index_node);
u.add(node.customer);
route = removal(route, node_toberemoved, index_node);
r.setLocations(route);
r.setDistance(distanceOneRoute(route));
r.setProfit(profitOneRoute(route));
checkCorrectNess(r, "remove customers eliminator");
}
}
else
{
if (prob.nextDouble() < Pl)
{
removed = true;
RouteNode node_toberemoved = node;
int index_node = route.indexOf(node);
route.remove(index_node);
u.add(node.customer);
route = removal(route, node_toberemoved, index_node);
r.setLocations(route);
r.setDistance(distanceOneRoute(route));
r.setProfit(profitOneRoute(route));
checkCorrectNess(r, "remove customers eliminator");
}
}
if (removed == false)
{
j++;
}
else
{
routesize = route.size();
total_profit = total_profit-node.customer.getProfit();
average_profit = total_profit/num_customers;
}
}
}
totalprofit = profitRoutes(routes);
}
public void addCustomers()
{
List<Customer> u_copy = new ArrayList<Customer>(u);
List<Customer> u_temp = new ArrayList<Customer>(u);
for (Customer c : u_temp)
{
boolean added = false;
for (ROUTE r : routes)
{
checkCorrectNess(r, "add customers eliminator");
if (added == true)
{
break;
}
Customer customer = c;
u_copy.remove(c);
List<RouteNode> route = r.getLocations();
for (int i = 0; i < route.size()-1; i++)
{
RouteNode possibleNode = new RouteNode();
possibleNode.customer = customer;
List<Integer> distances = calculateDistances(route.get(i), possibleNode, route.get(i+1));
// Calculate shift for customer under consideration
int arrivalTime = route.get(i).timeStartService+ route.get(i).customer.getService() + distances.get(0);
int wait = Math.max(0, customer.getOpeningTW()-arrivalTime);
int serviceDuration = customer.getService();
int shift = distances.get(0) + wait + serviceDuration + distances.get(2) - distances.get(1);
// Determine Start Service
int startServiceTime = Math.max(customer.getOpeningTW(), arrivalTime);
// Obtain waiting time of next customer
int waiting_next = route.get(i+1).wait;
// Obtain MaxShift of next customer
int maxShift = route.get(i+1).maxShift;
if (shift <= (waiting_next + maxShift) & startServiceTime <= customer.getClosingTW() )
{
// Customer can be inserted
added = true;
RouteNode newNode = new RouteNode();
newNode.customer = customer;
newNode.arrivalTime = arrivalTime;
newNode.timeStartService = startServiceTime;
newNode.shift = shift;
newNode.wait = wait;
int pos_insertion = i + 1;
route = ADD(route, newNode, pos_insertion);
r.setLocations(route);
r.setDistance(distanceOneRoute(route));
r.setProfit(profitOneRoute(route));
checkCorrectNess(r, "add customers eliminator");
// exit the last for loop
break;
}
}
}
if (added == false)
{
u_copy.add(c);
}
}
u = u_copy;
totalprofit = profitRoutes(routes);
}
/**
* Returns list of unvisited customers
* @return
*/
public List<Customer> getU()
{
return u;
}
/**
* Returns list of routes
* @return
*/
public List<ROUTE> getRoutes()
{
return routes;
}
}