遗传算法算任意表达式

最新推荐文章于 2020-07-17 10:19:18 发布

weixin_34414650

最新推荐文章于 2020-07-17 10:19:18 发布

阅读量119

点赞数

CC 4.0 BY-SA版权

原文链接：http://www.cnblogs.com/dannyboy/archive/2009/11/08/1598324.html

#pragma warning(disable: 4786)
#include <iostream>
#include<fstream>
#include<set>
#include <string>
#include <list>
#include <vector>

#include <math.h>
#include <time.h>
#include <conio.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdlib.h>
#include <process.h>
#include <float.h>

using namespace std;

#define POP_SIZE 40
#define CROSS_RATE 0.7
#define MUTATE_RATE 0.5
const int iteration_times=2000;

typedef struct
{
double code;//染色体
double degree;//适应度
}individual;

individual group[POP_SIZE];//种群规模为40

void max_evaluation(individual &x)
{
//根据sin2 (5. 1πx + 0. 5)的最大值
double tmp=sin(5.1*3.14*x.code+0.5)+sin(5.1*3.14*x.code+0.5)-sin(5.1*3.14*x.code+0.5);
x.degree=(tmp*tmp);
}

int happened(double p)//发生一个p=0~1间概率的事件
{
return rand()<(int)(p*RAND_MAX);
}

void cross(individual &x,individual &y)//交叉操作，产生一个子代取代父代中最次的一个
{
individual z;
z.code=(x.code+y.code)/2.0;
max_evaluation(z);

if(x.degree<y.degree)
{
  if(z.degree<=x.degree)return;
  //如果新个体不如双亲，淘汰之
  x=z;
}
else
{
  if(z.degree<=y.degree)return;
  y=z;
}
}
void mutate(individual &x)
{
x.code=x.code+rand();
max_evaluation(x);

}
double randfloat()
{
return (rand())/(RAND_MAX+1.0);
}

int roulette_wheel_selection(double A[],int n)
{
srand(time(0));
double t=randfloat();
int i;
double d=0.0;
for(i=0;i<n;i++)
{
d+=A[i];
if(d>t)return i;
}
return rand()%n;//这里出现的概率几乎为0，只有在精度丢失时才发生
}

void main()
{
srand(time(0));
int i,j,best ;
double sum;

for(i=0;i<POP_SIZE;++i)//随机得到初始种群
{
  group[i].code=1.0+(double)rand()/RAND_MAX;
  max_evaluation(group[i]);
}

////////////////////////////////////////////////////////
for(i=1;i<=iteration_times;++i)//固定进化10代
{
  sum=0.0;
  best=0;
  for(j=0;j<POP_SIZE;++j)
  {
   sum+=group[j].degree;//求总的适应度sum
   if(group[j].degree>group[best].degree)
    best=j;//求当前最优个体
  }

  printf("第%2d代中最优个体为 %10f\n",i,group[best].degree);
  ///////////////////////////////////
  double probability[POP_SIZE];
  memset(probability,0,sizeof(double)* POP_SIZE);

  for(j=0;j<POP_SIZE;++j)
  {
   probability[j]=group[j].degree/sum;
  }

  for(j=0;j<POP_SIZE;++j)
  {
   int sel1=roulette_wheel_selection(probability,POP_SIZE);
   int sel2=roulette_wheel_selection(probability,POP_SIZE);

   if(happened(CROSS_RATE)) cross (group[sel1],group[sel2]);//交叉
   if(happened(MUTATE_RATE)) mutate(group[sel1]);//变异

  }

}
system("pause");
}