【BP分类】基于鲸鱼算法优化BP神经网络实现数据分类
matlab代码
1 简介
随着人类社会的进步,科学技术的发展日新月异.模拟人脑神经网络的人工神经网络已取得了长足的发展.
经过半个多世纪的发展,人工神经网络在计算机科学,人工智能,智能控制等方面得到了广泛的应用. 当代社
会是一个讲究效率的社会,科技更新领域也是如此.在人工神经网络研究领域,算法的优化显得尤为重要,对
提高网络整体性能举足轻重.BP神经网络模型是目前应用最为广泛的一种神经网络模型,对于解决非线性
复杂问题具有重要的意义.但是BP神经网络有其自身的一些不足(收敛速度慢和容易陷入局部极小值问题),
在解决某些现实问题的时候显得力不从心.针对这个问题,本文利用遗传算法的并行全局搜索的优势,能够
弥补BP网络的不足,为解决大规模复杂问题提供了广阔的前景.本文将鲸鱼算法与BP网络有机地结合起来,
提出了一种新的网络结构,在稳定性,学习性和效率方面都有了很大的提高. 基于以上的研究目的,本文首先
设计了BP神经网络结构,在此基础上,应用鲸鱼算法进行优化,达到了加快收敛速度和全局寻优的效果.本文
借助MATLAB平台,对算法的优化内容进行了仿真实验,得出的效果也符合期望值,实现了对BP算法优化的
目的.
2 部分代码
%_________________________________________________________________________%%
Whale Optimization Algorithm (WOA) source codes demo 1.0 %%
%%
%%_________________________________________________________________________%% You
can simply define your cost in a seperate file and load its handle to fobj % The
initial parameters that you need are:%__________________________________________%
fobj = @YourCostFunction% dim = number of your variables% Max_iteration = maximum
number of generations% SearchAgents_no = number of search agents% lb=
[lb1,lb2,...,lbn] where lbn is the lower bound of variable n% ub=
[ub1,ub2,...,ubn] where ubn is the upper bound of variable n% If all the
variables have equal lower bound you can just% define lb and ub as two single
number numbers% To run ALO:
[Best_score,Best_pos,cg_curve]=ALO(SearchAgents_no,Max_iteration,lb,ub,dim,fobj)%
The Whale Optimization Algorithmfunction
[Leader_score,Leader_pos,Convergence_curve]=WOA(SearchAgents_no,Max_iter,lb,ub,d
im,fobj,handles,value)% initialize position vector and score for the
leaderLeader_pos=zeros(1,dim);Leader_score=inf; %change this to -inf for
maximization problems%Initialize the positions of search
agentsPositions=initialization(SearchAgents_no,dim,ub,lb);Convergence_curve=zero
s(1,Max_iter);t=0;% Loop counter% Main loopwhile t<Max_iter for
i=1:size(Positions,1) % Return back the search agents that go
beyond the boundaries of the search space Flag4ub=Positions(i,:)>ub;
Flag4lb=Positions(i,:)<lb; Positions(i,:)=(Positions(i,:).*(~
(Flag4ub+Flag4lb)))+ub.*Flag4ub+lb.*Flag4lb; % Calculate objective
function for each search agent fitness=fobj(Positions(i,:));
All_fitness(1,i)=fitness; % Update the leader if
fitness<Leader_score % Change this to > for maximization problem
Leader_score=fitness; % Update alpha Leader_pos=Positions(i,:);
end end a=2-t*((2)/Max_iter); % a decreases linearly fron 2 to
0 in Eq. (2.3) % a2 linearly dicreases from -1 to -2 to calculate t in Eq.
(3.12) a2=-1+t*((-1)/Max_iter); % Update the Position of search agents
for i=1:size(Positions,1) r1=rand(); % r1 is a random number in [0,1]
r2=rand(); % r2 is a random number in [0,1] A=2*a*r1-a; %
Eq. (2.3) in the paper C=2*r2; % Eq. (2.4) in the paper
b=1; % parameters in Eq. (2.5) l=(a2-1)*rand+1;
% parameters in Eq. (2.5) p = rand(); % p in Eq. (2.6)
for j=1:size(Positions,2) if p<0.5
if abs(A)>=1 rand_leader_index =
floor(SearchAgents_no*rand()+1); X_rand =
Positions(rand_leader_index, :); D_X_rand=abs(C*X_rand(j)-
Positions(i,j)); % Eq. (2.7) Positions(i,j)=X_rand(j)-
A*D_X_rand; % Eq. (2.8) elseif abs(A)<1
D_Leader=abs(C*Leader_pos(j)-Positions(i,j)); % Eq. (2.1)
Positions(i,j)=Leader_pos(j)-A*D_Leader; % Eq. (2.2)
end elseif p>=0.5
distance2Leader=abs(Leader_pos(j)-Positions(i,j)); % Eq. (2.5)
Positions(i,j)=distance2Leader*exp(b.*l).*cos(l.*2*pi)+Leader_pos(j);
end end end t=t+1;
Convergence_curve(t)=Leader_score; if t>2 line([t-1 t],
[Convergence_curve(t-1) Convergence_curve(t)],'Color','b')
xlabel('Iteration'); ylabel('Best score obtained so far');
drawnow end set(handles.itertext,'String', ['The current iteration is
', num2str(t)]) set(handles.optimumtext,'String', ['The current optimal value
is ', num2str(Leader_score)]) if value==1 hold on
scatter(t*ones(1,SearchAgents_no),All_fitness,'.','k') end end
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