MATLAB Answers


Returning an additional value that is not part of the fitness function or objective for all population evaluation in GA

Asked by Yaser Khojah on 22 Aug 2019
Latest activity Commented on by Yaser Khojah on 23 Aug 2019
Can anyone please help by showing the code how can I return an additional value (Sigma) that is not part of my fitness function (Mean). I know how to return all the populations, scores but I'm not sure how to return this additional value (sigma). I see many have asked this question but no one showed in a code rather than just directing us to use the nested functions. Here is my code:
% the function to be optimized
[objective] = Optimization_Function(x,Pi,Pa,LogG,d,lifetime,Demand,BasePrice,HighPrice,...
expectedNPV = mean(NPV_C);
sigma = std(NPV_C); %%%%% I need this value for every population evaluation
NewObjective = (expectedNPV)
objective = - NewObjective;
% my optimization code
clear gaoutfunction
options = optimoptions('ga','OutputFcn',@gaoutfunction,'UseParallel',true);
startTime = tic;
fun = @(x)Optimization_Function(x,Pi,Pa,LogNormal_G,d_cline,lifetime,Demand,BasePrice,...
[xGA,fval] = ga(fun,nvars,[],[],[],[],lowbond,upbond,[],[],options);
time_ga_parallel = toc(startTime);
record = gaoutfunction();
gapopulationhistory = vertcat(record.Population);
gabesthistory = vertcat(record.Best);
gascorehistory = vertcat(record.Score);
Results = [gapopulationhistory gascorehistory];
% my output funciton which includes populations, scores but does not include sigma :(
function [state,options,optchanged] = gaoutfunction(options,state,flag)
persistent state_record
if isempty(state_record)
state_record = struct('Population', {}, 'Best', {}, 'Score', {});
if nargin == 0
state = state_record;
options = [];
optchanged = [];
state_record(end+1) = struct('Population', state.Population, 'Best', state.Best', 'Score', state.Score);
optchanged = false;
Can anyone please show me how to return sigma as I’m returning all the populations and their scores. Please note the score here is only the objective which is the mean. The sigma value is not part of the optimization but I need it to save the time rather than running the model again to evaluate it. Please help.


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1 Answer

Answer by Matt J
on 22 Aug 2019
Edited by Matt J
on 22 Aug 2019
 Accepted Answer

function run_optimization
[xGA,fval] = ga(fun,nvars,[],[],[],[],lowbond,upbond,[],[],options);
% the function to be optimized
function [objective] = Optimization_Function(x,Pi,Pa,...) .
objective = - NewObjective;
allSigmas(end+1) = std(NPV_C); %%%%% I need this value for every population evaluation


Dear Matt, thanks for sharing this. I have tried and it is working. I never used parfor before. Do you think 'UseVectorized' is faster than using the parallel?
UseVectorized can be faster than parfor-parallelization when the fitness of all population members can be computed all at once without a for-loop. I assumed that that was not the case for you.

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