/***
* 计算y=-x(x-1)的最大值
* 取值范围x--[-2,2]
* @author BreezeDust
*
*/
#include<stdio.h>
class PSOTest {
public:
int n = 2; //粒子个数，这里为了方便演示，我们只取两个，观察其运动方向
double[] y;
double[] x;
double[] v;
double c1 = 2;
double c2 = 2;
double pbest[];
double gbest;
double vmax = 0.1;
public void fitnessFunction() {//适应函数
for (int i = 0; i<n; i++) {
y[i] = -1 * x[i] * (x[i] - 2);
}
}
public void init() { //初始化
x = new double[n];
v = new double[n];
y = new double[n];
pbest = new double[n];
/***
* 本来是应该随机产生的，为了方便演示，我这里手动随机落两个点，分别落在最大值两边
*/
x[0] = -0.5;
x[1] = 2.6;
v[0] = 0.01;
v[1] = 0.02;
fitnessFunction();
//初始化当前个体极值，并找到群体极值
for (int i = 0; i<n; i++) {
pbest[i] = y[i];
if (y[i]>gbest) gbest = y[i];
}
System.out.println("start gbest:" + gbest);
}
public double getMAX(double a, double b) {
return a>b ? a : b;
}
//粒子群算法
public void PSO(int max) {
for (int i = 0; i<max; i++) {
double w = 0.4;
for (int j = 0; j<n; j++) {
//更新位置和速度
v[j] = w * v[j] + c1 * Math.random()*(pbest[j] - x[j]) + c2 * Math.random()*(gbest - x[j]);
if (v[j]>vmax) v[j] = vmax;
x[j] += v[j];
//越界判断
if (x[j]>2) x[j] = 2;
if (x[j]<-2) x[j] = -2;
}
fitnessFunction();
//更新个体极值和群体极值
for (int j = 0; j<n; j++) {
pbest[j] = getMAX(y[j], pbest[j]);
if (pbest[j]>gbest) gbest = pbest[j];
System.out.println(x[j] + " " + v[j]);
}
System.out.println("======" + (i + 1) + "======gbest:" + gbest);
}
}
public static void main(String[] args) {
PSOTest ts = new PSOTest();
ts.init();
ts.PSO(100);
}
}
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