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Call function multiple times but execute once

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joshua Abam
joshua Abam 2019 年 12 月 7 日
Commented: joshua Abam 2020 年 1 月 3 日 22:40
Good Day all,
I am kind of stranded and I need all the helps I can possible get.
I have a main code which I am running, inside the main code I reference a function 3 times, the function is multple output, as such, each time I run the main function, it runs the reference function 3 times as well to extract all three output even when all the function are from the same source, which to me is kind of fustrating as it takes time to run the function one time, how much more running it three times. My challenge is how can I possible ajust the code so it can only runs the function one time.

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joshua Abam
joshua Abam 2019 年 12 月 11 日
Dear Walter,
Thanks for this piece of information it actually works fine.
Thanks
Joshua Abam
joshua Abam
joshua Abam 2019 年 12 月 12 日
Dear Walter
I have another concern, now I wish to paint a scenrio were 2 of the 3 output functions, are called in one function as stated below and 1 is called in another function. Now my question is I want it to run once instead of multiple times. Is there a way I can sort of arrange that.
Thanks
Joshua
eg.
function [c, ceq] = nonconst(x)
u = 20;
v = 40;
[total_value, ~, energy_value] = digital(x);
c = total_value-u*v;... ` `%first constrain
u*energy_value; %2nd constrain
ceq = [];
end
%let say I wish to make this the fitness function which is derived as one of the output from the 3 output.
function Delta_value = parcel(x)
[~, Delta_value, ~] = digital(x)
end
joshua Abam
joshua Abam 2020 年 1 月 3 日 22:40
Hi Walter
sorry I have not been able to respond to your messenge ealier
I have a scenerio playing in my head which i want to achieve, as I have explained earlier
The Challenge I am having is I wish to run both nonconst and parcel function one after the other however, I don't need the digital function to be run twice, as demostrated below. I wish the second function should be able to benefit from the first run.
Thanks
Joshua
eg.
function [c, ceq] = nonconst(x)
u = 20;
v = 40;
[total_value, Delta_value, energy_value] = digital(x);
c = total_value-u*v;... ` `%first constrain
u*energy_value; %2nd constrain
ceq = [];
end
function lineweight = parcel(x)
[total_value, Delta_value, energy_value] = digital(x);
p_s = 7850; %Density of steel Kg/m^3
g = 9.812; %Acceleration due to gravitation
k = 0.72
lineweight(1) = p_s*g*(pi/4)*(x(1)+x(2))*((x(3))^2-0.254^2);
lineweight(2) = k*Delta_value
T2 = table(x(1), x(2), x(3), lineweight(1), lineweight(2))
end

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採用された回答

Walter Roberson
Walter Roberson 2019 年 12 月 7 日

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joshua Abam
joshua Abam 2019 年 12 月 10 日
Dear Walter
I have used the memoize function hoiwever initial it look correct however on further examination it seems not to be, as it seems to be repeating the process which I am trying to eliminate in the first instance. Now if you go thru the code, when you call 'nonconst' function it start by calling 'total_value' function which is gotten from digital function, after that it calls 'energy_value' function and still repeat the calculation of the digital function that has been carried under total_value. My question are, is there a way to extract result from the previous run of the digital function without running the function afresh.
function [x,fval] = gafunction(x)
%Define at what Generation is GA stall
ObjectiveFunction = @parcel; %fitness function
nvars = 3; % Number of variables
A = []; %Linear Inequality Constraint matrix
b = []; %Linear inequality constraint vector
Aeq = []; %Linear equality Constraint matrix
beq = []; %Linear equality constraint vector
lb = [168, 400, 0.296]; %Vector of Lower bounds
ub = [172, 500, 0.312]; %Vector of Upper bounds
% Initial design point could be determined in 2 ways: One is to leave it to
% GA automatically generate; or it can be specified by the users.
%x0 = []; %Initial Feasible Point
nonlcon = @nonconst; %Nonlinear constraints
Intcon = []; %Vector indicating variables that take integer values
%Excuate GA with output
[x,fval] = ga(ObjectiveFunction,nvars,A,b,Aeq,beq,lb,ub,nonlcon,Intcon)
end
function lineweight = parcel(x)
%
p_s = 7850; %Density of steel Kg/m^3
g = 9.812; %Acceleration due to gravitation
lineweight = p_s*g*(pi/4)*(x(1)+x(2))*((x(3))^2-0.254^2);
T2 = table(x(1), x(2), x(3),lineweight)
end
function [D_total,D_value,D_energy] = digital(x)
% Your calculations
% ;;;;;;;;
% ;;;;;;;;
Dtetha = 180;
Dmax = 360-Dtetha;
% initialize the scores out of the loop
k = 1;
D_total = 0;
for direction = 0:Dtetha:Dmax
energy_direction = direction;
% Your calculations
%;;;;;;;;;;;;;;
% ;;;;;;;;;;;;;;
% scores = [2345,345,87,964,673,9843,763,783];
scores = 5768*[0.2326*x(1)+x(3),0.2552*x(2)+x(1)]; %,0.0234,0.0014,0.0062,0.0868,0.2108,0.1836];
weight = [507*x(3)^3, 459*x(1)^2]; %, 563, 764, 783, 2345, 6532, 5627];
density = [1.2, 8.4]; %, 5.6, 7.4, 9.8, 9.3, 6.2, 8.2];
score_value = scores(k); % % it possible till the length of the direction is equal to scores
weight_value = weight(k);% Your calculations
density_value = density(k);
% ;;;;;
% ;;;;;
D_auto = energy_direction*score_value*weight_value*density_value;
D_value = score_value*density_value;
D_energy = energy_direction*weight_value*density_value;
% Table_2 = table(wave_direction,scores(k))
% for n = 1:length(wave_direction)
D_total = D_total+ D_auto;
k = k+1; % increment count variable for each iteration
end
Table_1 = table(energy_direction, score_value, weight_value, density_value,D_auto, D_value, D_energy, D_total)
end
function [c, ceq] = nonconst(x)
u = 20;
v = 40;
c = total_value(x)-u*v;... ` `%first nonlinear constrain
u*energy_value(x);... %2nd Nonlinear constrain
v*Delta_value(x);
ceq = [];
end
function D_total = total_value(x)
D_total = digital(x) % ca
% fmem = memoize(@digital)
end
function D_energy = energy_value(x)
fmem = memoize(@digital) %to memoize the digital output
[~, ~, D_energy] = fmem(x)
end
function D_value = Delta_value(x)
fmem = memoize(@digital) %to memoize the digital output
[~, D_value, ~] = fmem(x)
end

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More Answers (1)

Steven Lord
Steven Lord 2019 年 12 月 10 日
I think it unlikely that ga is calling your function with exactly, down to the last bit, the same inputs multiple times. It's likely calling your function with inputs that are very close to one another, inputs that may even be displayed in the default format as the same, but that are very slightly different. Because of that memoization probably isn't going to help you.
Let me take a step back. Why do you want or need to try to reduce the number of calls ga makes to your function? Is it a performance consideration? Are the objective function evaluations expensive in terms of money (for example, are you planning to use ga to optimize parameters that require running a physical experiment for each set of parameters evaluated?) Is it a stylistic concern?
If you're concern is performance, what about the multiple calls to your objective function are the performance bottleneck? My strong suspicion is that it is your table call in the objective function as the other functions you call in your objective function require much less processing than creating a table. If you're doing this to show the parameter values after each iteration, depending on exactly why you need this information you may be able to instead specify an OutputFcn in some optimoptions that you pass into ga. See the section on ga options in the documentation for optimoptions for more information about the OutputFcn option.

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joshua Abam
joshua Abam 2019 年 12 月 10 日
Dear Steven
I am having a challenge, which I think, should be possible to overcome, but how to go about it has been challenging for me, I have a function with multiple output in this case 3 output, and I am calling all three output for further use. The issue now is how do I call the three output without repeating the entire calculation in the process. As I have observed that for the 3 times I called it, it runs afresh all 3 times. In the first place calling it once is time consuming how more calling it 3 times, whic makes the process computational expensive to achieve.
Thanks
Kind regards
function [c, ceq] = nonconst(x)
c = total_value(x)-u*v;... ` `%first nonlinear constrain
u*energy_value(x);... %2nd Nonlinear constrain
v*Delta_value(x);
ceq = [];
end
function D_total = total_value(x)
D_total = digital(x) % ca
end
function D_value = Delta_value(x)
%to memoize the digital output
[~, D_value, ~] = digital(x)
end
function D_energy = energy_value(x)
%to memoize the digital output
[~, ~, D_energy] = digital(x)
end
Rik
Rik 2019 年 12 月 10 日
As Steven explained: memoization only works if the input is exactly the same. That is why I suggested adding that code to your function. It will error if it runs twice with the same input. If it does run multiple times, that means the input wasn't the same.
Also, please use the tools explained on this page to make your code more readable.

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