waysun一路阳光

import java.io.File;
import static java.lang.Math.pow;
import static java.lang.Math.sqrt;
import static java.lang.Math.random;
import java.util.HashMap;
import java.io.FileReader;
import java.io.BufferedReader;
/**
*
* @author dvdface
*/

public class ACOforTSP {


//城市的距离表
private double[][] distance;
//距离的倒数表
private double[][] heuristic;
//启发信息表
private double[][] pheromone;
//权重
private int alpha, beta;
//迭代的次数
private int iterationTimes;
//蚂蚁的数量
private int numbersOfAnt;
//蒸发率
private double rate;

ACOforTSP (String file, int iterationTimes, int numbersOfAnt, int alpha, int beta, double rate) {

//加载文件
this.initializeData(file);
//初始化参数
this.iterationTimes = iterationTimes;
//设置蚂蚁数量
this.numbersOfAnt = numbersOfAnt;
//设置权重
this.alpha = alpha;
this.beta = beta;
//设置蒸发率
this.rate = rate;
}

private void initializeData(String filename) {

//定义内部类
class City {

int no;
double x;
double y;

City(int no, double x, double y) {

this.no = no;
this.x = x;
this.y = y;
}

private double getDistance(City city) {

return sqrt(pow((x - city.x), 2) + pow((y - city.y), 2));
}
}

try {
//定义HashMap保存读取的坐标信息
HashMap<Integer, City> map = new HashMap<Integer, City>();
//读取文件
BufferedReader reader = new BufferedReader(new FileReader(new File(filename)));
for (String str = reader.readLine(); str != null; str = reader.readLine()) {
//将读到的信息保存入HashMap
if (str.matches("([0-9]+)(\\s*)([0-9]+)(.?)([0-9]*)(\\s*)([0-9]+)(.?)([0-9]*)")) {

String[] data = str.split("(\\s+)");
City city = new City(Integer.parseInt(data[0]),
Double.parseDouble(data[1]),
Double.parseDouble(data[2]));

map.put(city.no, city);
}
}
//分配距离矩阵存储空间
distance = new double[map.size() + 1][map.size() + 1];
//分配距离倒数矩阵存储空间
heuristic = new double[map.size() + 1][map.size() + 1];
//分配信息素矩阵存储空间
pheromone = new double[map.size() + 1][map.size() + 1];
for (int i = 1; i < map.size() + 1; i++) {
for (int j = 1; j < map.size() + 1; j++) {
//计算城市间的距离，并存入距离矩阵
distance[j] = map.get(i).getDistance(map.get(j));
//计算距离倒数，并存入距离倒数矩阵
heuristic[j] = 1 / distance[j];
//初始化信息素矩阵
pheromone[j] = 1;
}
}

} catch (Exception exception) {

System.out.println("初始化数据失败！");
}
}

class Ant {

//已访问城市列表
private boolean[] visited;
//访问顺序表
private int[] tour;
//已访问城市的个数
private int n;
//总的距离
private double total;

Ant() {
//给访问顺序表分配空间
tour = new int[distance.length+1];
//已存入城市数量为n，刚开始为0
n = 0;
//将起始城市1,放入访问结点顺序表第一项
tour[++n] = 1;
//给已访问城市结点分配空间
visited = new boolean[distance.length];
//第一个城市为出发城市，设置为已访问
visited[tour[n]] = true;
}

private int chooseCity() {

//用来random的随机数
double m = 0;
//获得当前所在的城市号放入j,如果和j相邻的城市没有被访问，那么加入m
for (int i = 1, j = tour[n]; i < pheromone.length; i++) {

if (!visited) {
m += pow(pheromone[j], alpha) * pow(heuristic[j], beta);
}
}

//保存随机到的数
double p = m * random();
//寻找被随机到的城市
double k = 0;
//保存找到的城市
int q = 0;
for (int i = 1, j = tour[n]; k < p; i++) {

if (!visited) {

k += pow(pheromone[j], alpha) * pow(heuristic[j], beta);
q = i;
}
}

return q;
}

private void constructSolution () {

while (n != (distance.length-1) ) {

//选取下一个城市
int p = chooseCity();
//计算总的距离
total += distance[tour[n]][p];
//将选取到的城市放入已访问列表
tour[++n] = p;
//将选取到的城市标记为已访问
visited[p] = true;
}

//回到起点
total += distance[tour[1]][tour[n]];
//将起点加入访问顺序表的最后
tour[++n] = tour[1];
}

private void releasePheromone() {

//释放信息素的大小
double t = 1/total;
//释放信息素
for (int i=1;i<tour.length-1;i++) {

pheromone[tour][tour[i+1]] += t;
pheromone[tour[i+1]][tour] += t;
}
}

}

public void go() {

//保存最好的路径和路径长度
double bestTotal = Double.MAX_VALUE;
int[] bestTour = new int[distance.length+1];

//新建蚂蚁数组，用来引用所创建的蚂蚁
Ant[] ant = new Ant[numbersOfAnt];

//进行iterationTimes次迭代
while (iterationTimes != 0) {
//初始化新的一批蚂蚁（这里用构造新的蚂蚁代替重置蚂蚁状态）
for (int i=0; i<numbersOfAnt; i++) {
ant = new Ant();
}

//进行一次迭代（即让所有的蚂蚁构建一条路径）
for (int i=0; i<numbersOfAnt; i++) {

ant.constructSolution();
//如果蚂蚁构建的路径长度比上次最好的还好，那么保存这个长度和它所走的路径
if (ant.total<bestTotal) {

bestTotal = ant.total;
System.arraycopy(ant.tour, 1, bestTour, 1, bestTour.length-1);
}
}

//蒸发信息素
evaporatePheromone();

//释放信息素
for (int i=0; i<numbersOfAnt; i++) {

ant.releasePheromone();
}

//报告本次迭代的信息
System.out.format("本次为倒数第%d次迭代,当前最优路径长度为%10.2f\n",iterationTimes,bestTotal);

//迭代总数减去1，进行下次迭代
iterationTimes--;
}

//输出最好的路径长度
System.out.format("得到的最优的路径长度为:%10.2f\n",bestTotal);
//输出最好的路径
System.out.println("最优路径如下：");
for (int i=1; i<bestTour.length; i++) {

System.out.print("→"+bestTour);
}
}

private void evaporatePheromone() {

for (int i = 1; i < pheromone.length; i++)
for (int j = 1; j < pheromone.length; j++) {

pheromone[j] *= 1-rate;
}

}
}