use ga optimization but got error for ga process

Question

sogol bandekian 2022-5-10

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https://ww2.mathworks.cn/matlabcentral/answers/1715625-use-ga-optimization-but-got-error-for-ga-process

回答： Walter Roberson 2022-5-23

%fitness function Gomez and Levy
function y=fitnessfunctiongl(x)
x1=x(1);
x2=x(2);
y=(4*x1.^2)-2.1*x1.^4+1/3*x1.^6+(x1*x2)-4*x2.^2+4*x2.^4;
end
­­­­­%constraints
function [c ,ceq]=constraintgl(x)
x1=x(1);
x2=x(2);
c=-sin(4*pi*x1)+2*sin(2*pi*x2)^2-1.5;
ceq=[];
end
%main script to pass function and constraints to ga for optimization 
ObjFcn=@fitnessfunctiongl;
nvars=2;
lb=[-1, -1];
ub=[0.75, 1];
nonlcon=@constraintgl;
options = optimoptions('ga','ConstraintTolerance',1e-6,'Display','iter','PlotFcn',{@gaplotrange,@gaplotbestf,@gaplotselection,@gaplotmaxconstr}); %plotting the process of finding the solution 
%solution and function value
[x , fval,exitFlag,output,population,scores]= ga(ObjFcn,nvars,[],[],[],[],lb,ub,nonlcon,options);

----------------------------------but I got these errors------------------------------

Error in gadsplot (line 141)

[state,optimvalues] = callOnePlotFcn(fname,plotNames{i},state,options.OutputPlotFcnOptions,optimvalues,'init',args{i}{:});

Error in gacon (line 55)

state = gadsplot(options,state,'init','Genetic Algorithm');

Error in ga (line 406)

[x,fval,exitFlag,output,population,scores] = gacon(FitnessFcn,nvars, ...

Error in maingl (line 11)

[x , fval,exitFlag,output,population,scores]= ga(ObjFcn,nvars,[],[],[],[],lb,ub,nonlcon,options);

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Answer 1

Walter Roberson 2022-5-23

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1715625-use-ga-optimization-but-got-error-for-ga-process#answer_969795

在 MATLAB Online 中打开

syms x [1 2]

x1=x(1);

x2=x(2);

y=(4*x1.^2)-2.1*x1.^4+1/3*x1.^6+(x1*x2)-4*x2.^2+4*x2.^4;

c=-sin(4*pi*x1)+2*sin(2*pi*x2)^2-1.5;

sol1 = solve(c, x1)

sol1 =

eqn2 = subs(y, x1, sol1)

eqn2 =

sol2a = vpasolve(eqn2(1), x2)

sol2a =

sol2b = vpasolve(eqn2(2), x2)

sol2b =

0.087919847529159662140915717986356

back1a = vpa(subs(eqn2(1), x2, sol2a))

back1a =

back1b = vpa(subs(eqn2(2), x2, sol2b))

back1b =

ya = vpa(subs(y, {x1, x2}, {back1a, sol2a}))

ya =

yb = vpa(subs(y, {x1, x2}, {back1b, sol2b}))

yb =

Beyond this, you need to test at least one c value less than that equality, such as c=-sin(4*pi*x1)+2*sin(2*pi*x2)^2-1.6; in case the minima is not right at the constraint bound.

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Answer 2

Matt J 2022-5-10

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https://ww2.mathworks.cn/matlabcentral/answers/1715625-use-ga-optimization-but-got-error-for-ga-process#answer_960870

编辑：Matt J 2022-5-10

在 MATLAB Online 中打开

Perhaps you meant to have,

y=(4*x1.^2)-2.1*x1.^4+1/3*x1.^6+(x1*x2)-4*x1.^2+4*x2.^4;

or

y=(4*x1.^2)-2.1*x1.^4+1/3*x1.^6+(x1*x2)-4*x2.^2+4*x2.^4;

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sogol bandekian 2022-5-23

yes,you are right,thank you so much,but is there a way to increase the data on plots?

Alan Weiss 2022-5-23

You have nonlinear constraints. Therefore, the algorithm has few iterations, and plot functions are called just once per iteration. For an explanation of what nonlinear constraints do to the ga algorithm, see Nonlinear Constraint Solver Algorithms. For an example showing this behavior, see Constrained Minimization Using the Genetic Algorithm.

Alan Weiss

MATLAB mathematical toolbox documentation

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