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Error using MATLAB GA - [left and right sides have a different number of elements]

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Matheus Torquato
Matheus Torquato on 30 Jul 2021
Edited: Matheus Torquato on 11 Aug 2021
I'm running the MATLAB GA to optimise my objective function using:
var1 = (linspace(100, 400, 10));
var2 = (linspace(2, 7, 10));
for i=1:length(var2)
for j=1:length(var1)
objFun = @(x) my_objFun(var1(j),var2(i));
constraintFun = @(x) my_constraintFun(var1(j),var2(i));
try
[x,fval,exitflag,output]= ga(objFun,nvars,A,b,Aeq,beq,lb,ub,constraintFun,IntCon,options);
catch e
fprintf(1,'[ERROR] - The identifier was:\n%s\n',e.identifier);
fprintf(1,'[ERROR] - There was an error! The message was:\n%s\n',e.message);
end
end
end
The GA function is called repetitive times inside a loop. It sometimes runs successfully, other times it throws ERROR 1 and in a few other occasions it throws ERROR 2.
  • ERROR 1
[ERROR] - The identifier was:
MATLAB:matrix:singleSubscriptNumelMismatch
[ERROR] - There was an error! The message was:
Unable to perform assignment because the left and right sides have a different number of elements.
  • ERROR 2
[ERROR] - The identifier was:
MATLAB:griddedInterpolant:NonMonotonicCompVecsErrId
[ERROR] - There was an error! The message was:
Sample points must be unique and sorted in ascending order.
Any idea what that could be?
I'm using try and catches all over my my_objFun and my_constraintFun to make sure this error is not coming from there.
  3 Comments
Matheus Torquato
Matheus Torquato on 5 Aug 2021
Running it again using the for loop in reverse order did not change anything.
I did not see any difference as well when calling the GA with different outputs.
var1 = (linspace(100, 400, 10));
var2 = (linspace(2, 7, 10));
for i=length(var2):-1:1
for j=length(var1):-1:1
objFun = @(x) my_objFun(x,var1(j),var2(i));
constraintFun = @(x) my_constraintFun(x,var1(j),var2(i));
try
[~,fval,~,output]= ga(objFun,nvars,A,b,Aeq,beq,lb,ub,constraintFun,IntCon,options);
catch e
fprintf(1,'[ERROR] - The identifier was:\n%s\n',e.identifier);
fprintf(1,'[ERROR] - There was an error! The message was:\n%s\n',e.message);
end
end
end

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Answers (1)

Alan Weiss
Alan Weiss on 8 Aug 2021
I do not understand this line:
objFun = @(x) my_objFun(var1(j),var2(i));
Where does the variable x enter objFun? I think that is your main problem. Try calling
objFun(x0)
for some x0 that is a row vector with nvars elements. It probably will not return what you hope it returns.
Alan Weiss
MATLAB mathematical toolbox documentation
  1 Comment
Matheus Torquato
Matheus Torquato on 9 Aug 2021
Thank you for your comment.
I'm sorry about that. That was a typo while writing this snippet pseudocode.
I've corrected
objFun = @(x) my_objFun(var1(j),var2(i));
constraintFun = @(x) my_constraintFun(var1(j),var2(i));
to
objFun = @(x) my_objFun(x,var1(j),var2(i));
constraintFun = @(x) my_constraintFun(x,var1(j),var2(i));
This latter one is what I have been using in my code.

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