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可控变异:
假如我们有个二进制序列1111,转换为十进制就是15
若是我们将其变为1110,十进制变为14
若是我们将其变为1101,十进制变为13
变为1011,十进制变为11
变为0111,十进制变为7
也就是说,我们可以在大部分位置数据信息不变的情况下,各种幅度的改变我们的二进制序列代表的十进制信息。
适应值=目标函数值-f(x)下限
为了方便求概率才多了个这么个操作,
举几个例子
1.假设f(x)范围是[0,3]
那么三个个体函数值为[1,2,3],那么每个个体被取到的概率很自然我们就想到设置为[1,2,3]/(1+2+3)=[1/6,1/3,1/2],数值越大取到概率越大很正常
2.假设f(x)范围为[10,10.1]
三个个体函数值为[10.01,10.05,10.03],算出其概率为[0.3327,0.3340,0.3333]非常的接近,这是因为0.几的数对比与10太小了,因而减去10非常有必要。
3.假设f(x)范围为[-1,1]
万一有个体数值为负数总不能搞个负数概率叭,所以-(-1)也是很有必要的
综上我们看出Fmin的设置也需要有一定讲究,不能使适应值出现负数,也最好能使数据具有区分度,当然如果有更加合适的映射来代替线性映射也是极好(例如机器学习就常用sigmod函数来映射)。
假设我们有一个长度为4的二进制码,则其取值范围为0000至1111即[0,15];同时我们知道最优解范围是[2,3],我们只需要将二进制码转化为十进制,并且映射到最优解取值范围就好啦,
例如1011转换为十进制为11,从区间[0,15]映射到[2,3]即为,
(11-0)/(15-0)*(3-2)+2=2.7333,
从这个转换方式我们可以看出:
很多很多老版代码各种循环,这里能用向量运算就用向量运算,增加量程序的整洁度和速度
实例描述:
f
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x
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=
x
+
10
s
i
n
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5
x
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+
7
c
o
s
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4
x
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,
0
≤
x
≤
9
f(x)=x+10sin(5x)+7cos(4x),0\leq x\leq9
f(x)=x+10sin(5x)+7cos(4x),0≤x≤9
求
x
0
=
a
r
g
m
a
x
(
f
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x
)
)
x_0=argmax(f(x))
x0=argmax(f(x))即使
f
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x
)
f(x)
f(x)最大的
x
x
x值
使用代码:
[Count,Result,BestMember]=Genetic1(24,6,@(x)x+10*sin(5*x)+7*cos(4*x),0,9,15,0.9,200);
参数:
关于各个参数更详细的说明往后看
计算结果:

Count =200
Result =
7.8401,7.8048,7.8443,7.8403,7.8574,8.9649
24.8050,24.3683 ,24.8271,24.8066,11.1532,14.5649
BestMember =
7.8574
24.8553
即
x
=
7.8574
x=7.8574
x=7.8574时
f
(
x
)
f(x)
f(x)取最大值
24.8553
24.8553
24.8553
画个图看确实如此:

注:
遗传算法毕竟是智能算法,算出的值并不一定是最优解,因而可以调整迭代次数的大小,变异概率,二进制串长度,个体数量等一系列数据来调整,正因为各个变量比较难以说明为何这样设置,所以各种建模比赛还是尽量少用这样的智能算法。
function [Count,Result,BestMember]=Genetic1(MumberLength,MemberNumber,FunctionFitness,MinX,MaxX,Fmin,MutationProbability,Gen) % 参数解释: % 参数名 参数类型 参数含义 % ========================================================================= % MumberLength | 数值 | 表示一个染色体位串的二进制长度 % MemberNumber | 数值 | 表示群体中染色体个数 % FunctionFitness | 字符串 | 表示目标函数 % MinX | 数值 | 变量区间的下限 % MaxX | 数值 | 变量区间的上限 % Fmin | 数值 | 适应函数过程中给出目标函数可能最小值 % MutationProbability| 数值 | 变异概率 % Gen | 数值 | 遗传代数 % ------------------------------------------------------------------------- % Count | 数值 | 遗传代数 % Result | 数值 | 计算结果 % BestMember | 数值 | 最优个体及其适应值 global Count;Count=1;% 在之后的版本中可能会不支持函数输出作为全局变量(建议在改进工作中修改) global CurrentBest; % 声明全局变量Count(代数)和CurrentBest(当前代数下的最优染色体) % 随机地产生一个初始群体。 Population=PopulationInitialize(MumberLength,MemberNumber); PopulationCode=Population; % 计算群体中每一个染色体的目标函数值,适应函数值,入选概率 PopulationFitness=Fitness(PopulationCode,FunctionFitness,MinX,MaxX,MumberLength); PopulationFitnessF=FitnessF(PopulationFitness,Fmin); PopulationProbability=Probability(PopulationFitnessF); % 依据入选概率保留个体并记录最优个体 [Population,CurrentBest,EachGenMaxFitness]=Elitist(PopulationCode,PopulationFitness,MumberLength); EachMaxFitness(Count)=EachGenMaxFitness; MaxFitness(Count)=CurrentBest(MumberLength+1); while Count<Gen % 通过入选概率将入选概率大的个体选入种群,淘汰概率小的个体形成新群体 NewPopulation=Select(Population,PopulationProbability,MemberNumber); Population=NewPopulation; % 通过交叉互换形成新群体; NewPopulation=Crossing(Population); Population=NewPopulation; % 通过变异形成新群体 NewPopulation=Mutation(Population,MutationProbability); Population=NewPopulation; % 计算新群体中每一染色体的目标函数值并借此计算出适应值与入选概率 PopulationFitness=Fitness(Population,FunctionFitness,MinX,MaxX,MumberLength); PopulationFitnessF=FitnessF(PopulationFitness,Fmin); PopulationProbability=Probability(PopulationFitnessF); Count=Count+1; % 替换当前最优个体并将最劣个体用最优个体替换 [NewPopulation,CurrentBest,EachGenMaxFitness]=Elitist(Population,PopulationFitness,MumberLength); % EachMaxFitness,记录了第Count代中最优个体所对应的目标函数值; % MaxFitness,前Count代中最优个体所对应的目标函数值; EachMaxFitness(Count)=EachGenMaxFitness; MaxFitness(Count)=CurrentBest(MumberLength+1); Population=NewPopulation; end % 数据整理 Dim=size(Population); Result=ones(2,Dim(1)); for ii=1:Dim(1) Result(1,ii)=Translate(Population(ii,:),MinX,MaxX,MumberLength); end Result(2,:)=Fitness(Population,FunctionFitness,MinX,MaxX,MumberLength); BestMember(1,1)=Translate(CurrentBest(1:MumberLength),MinX,MaxX,MumberLength); BestMember(2,1)=CurrentBest(MumberLength+1); % 绘图 close all subplot(2,1,1) plot(EachMaxFitness); subplot(2,1,2) plot(MaxFitness); end
功能: 随机地产生一个初始群体。
输入变量:
输出变量: Poplation表示第一代群体
原理: 生成MemberNumber个长度为MumberLength的0-1向量
function Population=PopulationInitialize(MumberLength,MemberNumber)
Temporary=rand(MemberNumber,MumberLength);
Population=Temporary>=0.5;
% Population是一个逻辑矩阵(0-1矩阵,这么写为了方便),
% 在此函数中表示第一代群体,Population的每一行表示一个染色体
end
功能: 计算群体中每一个染色体的目标函数值。
输入参数:
输出变量:
PopulationFitness表示每一染色体对应的目标函数值
原理:
这部分就是把各个二进制码转换为十进制数(区间范围内),然后再带入到目标函数中算出数值。
说明: 由于懒,这里把网上大部分代码中的Translate函数和Transfer函数也合了进去,没必要为了两行运算多开俩函数吧。。。
function PopulationFitness=Fitness(PopulationCode,FunctionFitness,MinX,MaxX,MumberLength)
Dim=size(PopulationCode);
PopulationFitness=zeros(1,Dim(1));
for i=1:Dim(1)
% 转换为10进制
PopulationData=sum(PopulationCode(i,:).*(2.^(MumberLength-1:-1:0)));
% 映射到x取值范围
PopulationData=MinX+PopulationData*(MaxX-MinX)/(2^Dim(2)-1);
% 计算对应f(x)数值
PopulationFitness(i)=FunctionFitness(PopulationData);
end
end
功能: 计算每个染色体的适应函数值
输入参数:
PopulationFitness表示目标函数值;
Fmin表示目标函数的可能的最小值;
输出参数: PopulationFitnessF表示每一染色体的适应函数值
function PopulationFitnessF=FitnessF(PopulationFitness,Fmin)
% 若某一染色体的目标函数值大于Fmin,则置其适应函数值为其目标函数值-Fmin
% 若某一染色体的目标函数值小于Fmin,则置其适应函数值为0
PopulationFitnessF=PopulationFitness-Fmin;
PopulationFitnessF(PopulationFitnessF<0)=0;
end
这部分代码已经包含在Fitness函数内了,再写一遍是专门用来服务于最后的结果输出的。
function PopulationData=Translate(PopulationCode,MinX,MaxX,MumberLength)
Dim=size(PopulationCode);
PopulationData=sum(PopulationCode.*(2.^(MumberLength-1:-1:0)));
PopulationData=MinX+PopulationData*(MaxX-MinX)/(2^Dim(2)-1);
end
就是将适应值转换为概率,其方法就是除以所有适应值的和
function PopulationProbability=Probability(PopulationFitnessF)
PopulationProbability=PopulationFitnessF./sum(PopulationFitnessF);
end
根据入选概率在群体中按比例选择部分染色体组成种群
function NewPopulation=Select(Population,PopulationProbability,MemberNumber)
% 概率密度转换为概率分布
CProbability=PopulationProbability(1);
for i=2:MemberNumber
CProbability(i)=CProbability(i-1)+PopulationProbability(i);
end
% 摇随机数并依据随机数和概率选择个体
pmat=rand([MemberNumber,1]);
index=sum((pmat>=CProbability),2)+1;
NewPopulation=Population(index,:);
end
群体中的交叉并产生新群体,原理描述如下:

我们每次都是两个相邻的进行交叉,这样如果个体数为奇数,则最后一个个体则一直无法参与互换,因此我们每次都将倒数第一和倒数第二个体换位置,这样倒数第一位和倒数第二位就能够轮流参与交叉互换。(当然其实直接整体全部交换顺序也可以)
function NewPopulation=Crossing(Population)
Dim=size(Population);
if Dim(1)>=3
Population([Dim(1),Dim(1)-1],:)=Population([Dim(1)-1,Dim(1)],:);
% 若群体中个体数大于等于3,则将最后一个个体与倒数第二个个体基因型互换;
% 目的是防止有个体从始至终未参与交叉。
end
for i=1:2:Dim(1)-1
% 相邻的俩个体交叉互换
Site=randi(Dim(2));
Population([i,i+1],1:Site)=Population([i+1,i],1:Site);
end
NewPopulation=Population;
end
想改成全部互换则可写做:
function NewPopulation=Crossing(Population)
Dim=size(Population);
Population(1:Dim,:)=Population(randperm(Dim(1)),:);
for i=1:2:Dim(1)-1
Site=randi(Dim(2));
Population([i,i+1],1:Site)=Population([i+1,i],1:Site);
end
NewPopulation=Population;
end
为每个个体摇个随机数,如果随机数符合变异概率,就随机将该个体其中一个0变为1或将1变为0
function NewPopulation=Mutation(Population,MutationProbability)
Dim=size(Population);
for i=1:Dim(1)
Probability=rand(1);
Site=randi(Dim(2));
if Probability<MutationProbability
Population(i,Site)=mod(Population(i,Site)+1,2);
end
end
NewPopulation=Population;
end
功能: 如果当前序列中有个体优于历史最优则更新历史最优,同时将当前个体组中最差个体用历史最优代替。
输入变量:
输出变量:
function [NewPopulationIncludeMax,NewCurrentBest,EachGenMaxFitness]=... Elitist(Population,PopulationFitness,MumberLength) % 找到当前种群最优和最差个体 [~,MinSite]=min(PopulationFitness); [MaxFitnesstemp,MaxSite]=max(PopulationFitness); EachGenMaxFitness=MaxFitnesstemp; % 更新历史最优 if Count==1 CurrentBest(1:MumberLength)=Population(MaxSite,:); CurrentBest(MumberLength+1)=PopulationFitness(MaxSite); else if CurrentBest(MumberLength+1)<MaxFitnesstemp CurrentBest(1:MumberLength)=Population(MaxSite,:); CurrentBest(MumberLength+1)=PopulationFitness(MaxSite); end % 当前种群最差用历史最优代替 Population(MinSite,:)=CurrentBest(1:MumberLength); end NewPopulationIncludeMax=Population; NewCurrentBest=CurrentBest; end
把所有代码合在了一起
function [Count,Result,BestMember]=Genetic1(MumberLength,MemberNumber,FunctionFitness,MinX,MaxX,Fmin,MutationProbability,Gen) % 参数解释: % 参数名 参数类型 参数含义 % ========================================================================= % MumberLength | 数值 | 表示一个染色体位串的二进制长度 % MemberNumber | 数值 | 表示群体中染色体个数 % FunctionFitness | 字符串 | 表示目标函数 % MinX | 数值 | 变量区间的下限 % MaxX | 数值 | 变量区间的上限 % Fmin | 数值 | 适应函数过程中给出目标函数可能最小值 % MutationProbability| 数值 | 变异概率 % Gen | 数值 | 遗传代数 % ------------------------------------------------------------------------- % Count | 数值 | 遗传代数 % Result | 数值 | 计算结果 % BestMember | 数值 | 最优个体及其适应值 global Count;Count=1;% 在之后的版本中可能会不支持函数输出作为全局变量(建议在改进工作中修改) global CurrentBest; % 声明全局变量Count(代数)和CurrentBest(当前代数下的最优染色体) % 随机地产生一个初始群体。 Population=PopulationInitialize(MumberLength,MemberNumber); PopulationCode=Population; % 计算群体中每一个染色体的目标函数值,适应函数值,入选概率 PopulationFitness=Fitness(PopulationCode,FunctionFitness,MinX,MaxX,MumberLength); PopulationFitnessF=FitnessF(PopulationFitness,Fmin); PopulationProbability=Probability(PopulationFitnessF); % 依据入选概率保留个体并记录最优个体 [Population,CurrentBest,EachGenMaxFitness]=Elitist(PopulationCode,PopulationFitness,MumberLength); EachMaxFitness(Count)=EachGenMaxFitness; MaxFitness(Count)=CurrentBest(MumberLength+1); while Count<Gen % 通过入选概率将入选概率大的个体选入种群,淘汰概率小的个体形成新群体 NewPopulation=Select(Population,PopulationProbability,MemberNumber); Population=NewPopulation; % 通过交叉互换形成新群体; NewPopulation=Crossing(Population); Population=NewPopulation; % 通过变异形成新群体 NewPopulation=Mutation(Population,MutationProbability); Population=NewPopulation; % 计算新群体中每一染色体的目标函数值并借此计算出适应值与入选概率 PopulationFitness=Fitness(Population,FunctionFitness,MinX,MaxX,MumberLength); PopulationFitnessF=FitnessF(PopulationFitness,Fmin); PopulationProbability=Probability(PopulationFitnessF); Count=Count+1; % 替换当前最优个体并将最劣个体用最优个体替换 [NewPopulation,CurrentBest,EachGenMaxFitness]=Elitist(Population,PopulationFitness,MumberLength); % EachMaxFitness,记录了第Count代中最优个体所对应的目标函数值; % MaxFitness,前Count代中最优个体所对应的目标函数值; EachMaxFitness(Count)=EachGenMaxFitness; MaxFitness(Count)=CurrentBest(MumberLength+1); Population=NewPopulation; end % 数据整理 tDim=size(Population); Result=ones(2,tDim(1)); for ii=1:tDim(1) Result(1,ii)=Translate(Population(ii,:),MinX,MaxX,MumberLength); end Result(2,:)=Fitness(Population,FunctionFitness,MinX,MaxX,MumberLength); BestMember(1,1)=Translate(CurrentBest(1:MumberLength),MinX,MaxX,MumberLength); BestMember(2,1)=CurrentBest(MumberLength+1); % 绘图 close all subplot(2,1,1) plot(EachMaxFitness); subplot(2,1,2) plot(MaxFitness); %子函数部分 %========================================================================== %PopulationInitialize:用于产生一个初始群体,这个初始群体含有MemberNumber %个染色体,每个染色体含有MumberLength个基因。 function Population=PopulationInitialize(MumberLength,MemberNumber) Temporary=rand(MemberNumber,MumberLength); Population=Temporary>=0.5; end %Fitness: 用于计算群体中每一个染色体的目标函数值 function PopulationFitness=Fitness(PopulationCode,FunctionFitness,MinX,MaxX,MumberLength) Dim=size(PopulationCode); PopulationFitness=zeros(1,Dim(1)); for i=1:Dim(1) PopulationData=sum(PopulationCode(i,:).*(2.^(MumberLength-1:-1:0))); PopulationData=MinX+PopulationData*(MaxX-MinX)/(2^Dim(2)-1); PopulationFitness(i)=FunctionFitness(PopulationData); end end %FitnessF: 用于计算每个染色体适应值 function PopulationFitnessF=FitnessF(PopulationFitness,Fmin) PopulationFitnessF=PopulationFitness-Fmin; PopulationFitnessF(PopulationFitnessF<0)=0; end %Translate function PopulationData=Translate(PopulationCode,MinX,MaxX,MumberLength) Dim=size(PopulationCode); PopulationData=sum(PopulationCode.*(2.^(MumberLength-1:-1:0))); PopulationData=MinX+PopulationData*(MaxX-MinX)/(2^Dim(2)-1); end %Probability: 用于计算每个染色体入选概率 function PopulationProbability=Probability(PopulationFitnessF) PopulationProbability=PopulationFitnessF./sum(PopulationFitnessF); end %Elitist: 使用最佳个体保存法,输入参数为: %Population 群体 %PopulationFitness 目标函数值 %MutationProbability 变异概率 function [NewPopulationIncludeMax,NewCurrentBest,EachGenMaxFitness]=... Elitist(Population,PopulationFitness,MumberLength) [~,MinSite]=min(PopulationFitness); [MaxFitnesstemp,MaxSite]=max(PopulationFitness); EachGenMaxFitness=MaxFitnesstemp; if Count==1 CurrentBest(1:MumberLength)=Population(MaxSite,:); CurrentBest(MumberLength+1)=PopulationFitness(MaxSite); else if CurrentBest(MumberLength+1)<MaxFitnesstemp CurrentBest(1:MumberLength)=Population(MaxSite,:); CurrentBest(MumberLength+1)=PopulationFitness(MaxSite); end Population(MinSite,:)=CurrentBest(1:MumberLength); end NewPopulationIncludeMax=Population; NewCurrentBest=CurrentBest; end %Select: 根据入选概率,在群体中按比例选择部分染色体组成种群 function NewPopulation=Select(Population,PopulationProbability,MemberNumber) % 概率密度转换为概率分布 CProbability=PopulationProbability(1); for i=2:MemberNumber CProbability(i)=CProbability(i-1)+PopulationProbability(i); end % 摇随机数并依据随机数和概率选择个体 pmat=rand([MemberNumber,1]); index=sum((pmat>=CProbability),2)+1; NewPopulation=Population(index,:); end %Crossing: 用于群体中的交叉并产生新群体 function NewPopulation=Crossing(Population) Dim=size(Population); Population(1:Dim,:)=Population(randperm(Dim(1)),:); % if Dim(1)>=3 % Population([Dim(1),Dim(1)-1],:)=Population([Dim(1)-1,Dim(1)],:); % end for i=1:2:Dim(1)-1 Site=randi(Dim(2)); Population([i,i+1],1:Site)=Population([i+1,i],1:Site); end NewPopulation=Population; end %Mutation: 用于群体中少量个体变量并产生新的群体 function NewPopulation=Mutation(Population,MutationProbability) Dim=size(Population); for i=1:Dim(1) Probability=rand(1); Site=randi(Dim(2)); if Probability<MutationProbability Population(i,Site)=mod(Population(i,Site)+1,2); end end NewPopulation=Population; end end
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