Java实现简单GA算法求函数极值

import java.security.SecureRandom; import java.util.Random; public class GetMaxValue { //定义样本数 static int N = 10; //定义DNA位数 static int M = 5; //定义样本DNA数组 static int[][] DNA = new int[N][M]; //定义样本表现值 static int[] show = new int[N]; //定义样本存活累计概率0-1 static double[] alive = new double[N]; //定义淘汰阈值 static int sigma = 3; //定义繁衍代数 static int T = 500; //定义交换基因次数 static int C = 1; //将样本10进制求2进制 j表示位数 static void tentotwo() { for (int i = 0; i < N;i++ ) { int j = 0; int tempshow = show[i]; while (tempshow != 0) { DNA[i][j] = tempshow% 2; tempshow /= 2; j++; } } } //将样本2进制转10进制 static void twototen() { for (int i = 0; i < N; i++) { int sum = 0; for(int j=0;j<M;j++) { sum += DNA[i][j]*(int)Math.pow(2, j); } show[i] = sum; } } //适应度函数 static int f(int x) { int result = -x * x + 31*x; return (result); } //求累计存活概率函数 static void icanlive() { int sum = 0; double alivesum = 0; for (int i = 0; i < N; i++) { sum += f(show[i]); } for (int i = 0; i < N; i++) { alivesum += (double)f(show[i]) / (double)sum; alive[i] = alivesum; } } //淘汰函数 static void dieout() { int[] times = new int[N]; for (int i = 0; i < times.length;i++ ) { times[i] = 0; } Random ro = new Random(); //遗传过程 for (int i = 0; i < 2*N; i++) { double myro = (double)ro.nextInt(100)/ 100; for (int j = 0; j < N; j++) { if (myro<alive[j]) { if (j != 0 && myro > alive[j - 1]) { times[j] += 1; break; } else if(j==0) { times[j] += 1; break; } } } } //找出本次遗传中最强势种族 int max = times[0]; int sign = 0; for (int y = 0; y < N; y++) { if (times[y] > max) { max = times[y]; sign = y; } } for (int y = 0; y < N; y++) { //小于阈值的样本被淘汰，改样本被适应度最强的样本取代 if (times[y] < sigma) { show[y] = show[sign]; } } } static void exchangeDNA() { Random ro = new Random(); int a; int b; int x1; int x2; int y1; int y2; int iUp1 = M, iUp2 = N; int iDown = 0; int temp; for (int i = 0; i < C; i++) { x1 = ro.nextInt(iUp1); x2 = ro.nextInt(iUp1); y1 = ro.nextInt(iUp1); y2 = ro.nextInt(iUp1); a = ro.nextInt(iUp2); b = ro.nextInt(iUp2); temp = DNA[a][x1]; DNA[a][ x1] = DNA[b][ y1]; DNA[b][ y1] = temp; temp = DNA[a][ x2]; DNA[a][ x2] = DNA[b][ y2]; DNA[b][ y2] = temp; } } static int Max (int[]shuzu) { int temp=0; for(int i=0;i<shuzu.length;i++) { if(shuzu[i]>temp) { temp=shuzu[i]; } } return temp; } static int Min (int[]shuzu) { int temp=100000000; for(int i=0;i<shuzu.length;i++) { if(shuzu[i]<temp) { temp=shuzu[i]; } } return temp; } public static void main(String[] args) { //初始化样本值 show[0] = 1; show[1] = 2; show[2] = 23; show[3] = 12; show[4] = 4; show[5] = 7; show[6] = 9; show[7] = 20; show[8] = 29; show[9] = 10; tentotwo(); System.out.println("\n父代样本\n"); System.out.println("样本表现值："); for (int j = 0; j < N; j++) { System.out.println(String.valueOf(show[j]) + "　"); } System.out.println("\n样本适应度："); for (int j = 0; j < N; j++) { System.out.println(String.valueOf(f(show[j])) + "　"); } for (int i = 0; i < T;i++ ) { //交换DNA exchangeDNA(); //DNA触发变现值 twototen(); //表现值求出存活概率 icanlive(); //根据存活概率淘汰低者 dieout(); //表现值触发DNA tentotwo(); double max = Max(show); double min = Min(show); System.out.println("\n\n第" + (i + 1) + "代样本\n"); System.out.println("样本表现值："); for (int j = 0; j < N; j++) { System.out.println(String.valueOf(show[j])+""); } System.out.println("\n样本适应度："); for (int j = 0; j < N; j++) { System.out.println(String.valueOf(f(show[j]))+""); } //if (max == min) //{ // break; //} } System.out.println("\n\n程序运行完毕\n"); } }