'UseParallel' with particleswarm() when objective function calls Simulink model

Otavio Bertozzi

2022 3 1

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Hello,

I am optimizing some simulink model parameters using particleswarm().

I do not have experience with parallel computing, but I believe I reached the moment when I need it...

I would like to get some advice on what I need to change in my objective function so that it works in parallel (serial computing runs with no errors)

My main code is:

close all

clear

clc

% Define global variable with model name

global mdl;

mdl='Sim_exp';

% Load parameters to base workspace

sim_init_exp;

% Set upper and lower bounds on optimization parameter

lb_gains = [0 0];

ub_gains = [50 50];

% Solver options

options = optimoptions('particleswarm');

options = optimoptions(options,'UseParallel',true);

options = optimoptions(options,'PlotFcn', { @pswplotbestf });

% Run PSO

[opt_PI,~,~,~] = particleswarm(@obj_fcn,2,lb_gains,ub_gains,options);

my objective function is:

function [out] = obj_fcn(K)

% Access global variable

global mdl;

% Change parameter values in base workspace

assignin('base','Kp',K(1))

assignin('base','Ki',K(2))

% Simulate model

sim(mdl);

% Load results

ref1=curr_refs.Data(:,1);

ref2=curr_refs.Data(:,2);

meas1=curr_meas.Data(:,1);

meas2=curr_meas.Data(:,2);

ang1=alpha_angles.Data(:,1);

ang2=alpha_angles.Data(:,2);

mid=round(length(ref1)/2);

% Compute objective function value

fa1=trapz(abs(ref1-meas1))+trapz((ref1-meas1).^2);

fa2=trapz(abs(ref2-meas2))+trapz((ref2-meas2).^2);

fb11=abs(ref1(1)-max(meas1(1:mid)))+abs(ref1(end)-max(meas1(mid:end)));

fb12=abs(ref1(1)-min(meas1(1:mid)))+abs(ref1(end)-min(meas1(mid:end)));

fb21=abs(ref2(1)-max(meas2(1:mid)))+abs(ref2(end)-max(meas2(mid:end)));

fb22=abs(ref2(1)-min(meas2(1:mid)))+abs(ref2(end)-min(meas2(mid:end)));

out=((fa1+fa2)*1e-4)+fb11+fb12+fb21+fb22;

end

From the errors I get when I try to run this code with 'UseParallel' true, it seems I should also parallelize the simulation inside my objective fcn, but I don't know where to start.

Could you please advise?

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Alvaro 2022-12-27

Could you post the error message that you are getting?

As a first guess for troubleshooting, I would consider getting rid of that global variable and just passing it directly into the function. See many answers related to this issue:

https://www.mathworks.com/matlabcentral/answers/?term=global+variables+parfor

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