How would I get Maximization curve in GA in Matlab?

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SUMAN CHATTERJEE 2019-2-25

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评论： Mohammed Bakr 2020-11-25

In GA toolbox in Matlab we are getting fitness curve in form of minimization. How can I get maximization (fitness function) curve?

Can anyone help me in getting GA code for optimization?

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Answer 1

Walter Roberson 2019-2-25

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https://ww2.mathworks.cn/matlabcentral/answers/446830-how-would-i-get-maximization-curve-in-ga-in-matlab#answer_362592

在 MATLAB Online 中打开

minimize the negative of the function.

  [x, fvalp] = ga(@(x) -f(x), ....)
  fval = -fvalp;     %maximum value of the original function

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Mohammed Bakr 2020-11-25

编辑：Walter Roberson 2020-11-25

在 MATLAB Online 中打开

now i donot have any error but iam sorry can you tell me exactely where i do @(x)-mohfun(x)

my function code

function [e] = mohfun(r)
dt = r(1);
ltt = r(2);
dss = r(3); 
%% Data of cold fluid 
tci=30;                                                                    %Input temperature of cold fluid (C)
%tco=35;                                                                   %Output temperature of cold fluid (C)
rowc=1000;                                                                 %Density (kg/m3)
mioc=0.000797;                                                             %Viscosity (Pa s)
kc=.613;                                                                   %Thermal conductivity (W/m K)
prc=5.83;                                                                  %Prandtl number
cpc=4186;                                                                  %Heat capacity (kJ/kg K)
mc=42;                                                                     %Mass flow rate of cold fluid 
vec=1.14;                                                                  %velocity of cold fluid
%rec;                                                                      %Reynold’s number OF COLD fluid
%hc;                                                                       %hot stream of cold fluid
%ftc,                                                                      %Darcy friction factor of cold fluid 
%qc=input('Enter heat duty of cold fluid = ');                             %heat duty (W)
%% Data of hot fluid 
thi=60;                                                                    %Input temperature of hot stream (C)
%tho=45;                                                                   %Output temperature of hot stream (C)
rowh=865.8;                                                                %Density (kg/m3)
mioh=0.023;                                                           %Viscosity (Pa s)
kh=0.141;                                                              %Thermal conductivity (W/m K)
prh=1205;                                                                  %Prandtl number
cph=2000;                                                                  %Heat capacity (kJ/kg K)
mh=17.2;                                                                   %Mass flow rate
%veh=1.5;                                                                  %velocity of hot fluid
%qh=input('Enter heat duty of hot fluid = ');                              %heat duty (W)
%pit=.005;                                                                  %triangular pitch
%res                                                                       %reynolds number (res) for shell side
%hs                                                                        %hot stream of hot fluid
%% data of tube
%nt=input('Enter number of tube = ');                                      %number of tube
dti=dt;                                                                    %Tube inside diameter (m)
st=0.0043;                                                                 %Tube thickness (m)
Rft=0.00042;                                                               %fouling factor 
%dto                                                                       %outer dimeter of tube  
lt=ltt; %lt=input('Enter the length of tube = ');                          %Tubes length (m)
%% Data of shell
ds=dss;                                                                    %Shell inside diameter (m)
np=1;                                                                      %Number of tube passes
Rfs=0.0002;                                                                     %fouling factor 
%dh                                                                        %hydraulic diameter
%% Equation
fprintf('dti %f \n ',dti)
fprintf('ltt %f \n ',ltt)
fprintf('dss %f \n ',dss)
dto=dti+st;
fprintf('dto %f \n ',dto)
%nt=mc/(rowc*(pi/4)*(dti^2)*vec);
v1=pi/4;
v2=dti^2;
v3=rowc*v2;
v4=v3*v1*vec;
nt=mc/v4;
ntt=nt*2;
fprintf('nt %f \n',nt)
%nt=nt1*2;
fprintf('ntt %f \n',ntt)
as=pi*dto*lt*nt*np;
fprintf('as %f \n',as)
rec = (rowc*vec*dti)/(mioc);
fprintf('rec %f \n',rec)
ftc = ((1.82*log(rec))-1.64)^(-2);
fprintf('ftc %f \n',ftc)
if rec < 2300
    
    hc = (kc/dti)*(3.657+((0.0677*rec*prc*(dti/3.050))^1.33)/(1+0.1*prc*((rec*(dti/3.050))^0.3)));
    
elseif 2300 < rec && rec < 10000
    
    hc = (kc/dti)*((1+(dti/3.050))^0.67)*(((ftc/8)*(rec-1000)*(prc))/(1+12.7*((ftc/8)^0.5)*((prc^0.667)-1)));
    
elseif rec > 10000
    
    hc = (0.027)*(kc/dti)*(rec^0.8)*(prc^(1/3))*(mioc/mioc)^0.14;
    
end
fprintf('hc %f \n',hc)
%dh = (4*(0.43*pit^2-(pi*0.125*dto^2)))/(0.5*pi*dto);
%d1=ds^2-(dto^2*nt);
%d2=ds+(dto*nt);
%dh=d1/d2;
dh=(ds^2-(dto^2*nt))/(ds+(dto*nt));
fprintf('dh %f \n',dh)
f1=pi/4;
f2=f1*dh^2;
f3=f2*rowh;
veh=mh/f3;
fprintf('veh %f \n',veh)
res=(rowh*veh*dh)/mioh;
fprintf('res %f \n',res)
hs=(0.36*kh*res^0.55*prh^0.33)/dh;
fprintf('hs %f \n',hs)
%U = ((1/hs)+Rfs+(dto/dti)*(Rft+(1/hc)))^(-1);
U = ((1/hs)+Rfs+Rft+(1/hc))^(-1);
fprintf('U %f \n',U)
c1=mc*cpc;
fprintf('c1 %f \n',c1)
c2=mh*cph;
fprintf('c2 %f \n',c2)
if c1>c2 
    c_x=c1; 
    c_m=c2;  
else
    c_x=c2; 
    c_m=c1;
end
fprintf('c_m %f \n',c_m)
fprintf('c_x %f \n',c_x)
ntu= (as*U)/c_m;
fprintf('ntu %f \n',ntu)
cr=c_m/c_x;
fprintf('cr %f \n',cr)
%ef=1-exp(-cr^-1 * (1-exp(1-cr(ntu))));
e1=exp(-cr*ntu);
e2=1-e1;
e3=-cr^-1;
e4=e3*e2;
e5=exp(e4);
ef=1-e5;
%e7=1+e6;
%ef=1/e7;
e=-ef;
fprintf('ef %f \n',ef)
tho=thi-ef*(thi-tci);
fprintf('tho %f \n',tho)
qh=mh*cph*(thi-tho);
fprintf('qh %f \n',qh)
tco=(qh/(mc*cpc))+tci;
fprintf('tco %f \n',tco)
lt= as/(pi*dto*nt);
fprintf('lt %f \n',lt)
end

Walter Roberson 2020-11-25

You see in the Plot function section where you ask to plot best fitness? You would need to change that to a custom plot function that worked just like the plot function for best fitness but plotted the negative of the current value. See https://www.mathworks.com/help/gads/genetic-algorithm-options.html#f15210

There is no built-in way to maximize values using the solver-based approach: all you can do is minimize the negative of the function and understand that what you will get out is the location of the maxima, and that you need to take the negative of any function value you get out of your @(x)-mofun(x) function in order to know what the value would be in your original @mofun space.

Mohammed Bakr 2020-11-25

thank you too much

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How would I get Maximization curve in GA in Matlab?

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