Arrays have incompatible sizes for this operation error

Hello i am working on an optimization problem where i have 2 dec. variables x and y. x is a matrix with dimensions 36x36 and y is 36x1. my objective function only uses one of the variables which is x. but since my number of variables is 1332= (1296 +36). Now my objective function gives this error. Arrays have incompatible sizes for this operation error.

Here is my objective function looks like ;

function z = objectivefunc(x,rij,ai)

z= (-1)*sum(x.*rij.*ai,'all');

end

rij and ai are my parameters. (rij 36x36, ai 36x1 ).

Thank you in advance.

Answer 1

[Alan Weiss]

It looks like the issue is that ai is not 36-by-36. You probably want something like

ai = repmat(ai,1,36);
z= (-1)*sum(x.*rij.*ai,'all');

Alan Weiss

MATLAB mathematical toolbox documentation

[Azime Beyza Ari]

No it did not solve the problem. I think problem is casued because this;

my x variables are 1296

and since i have another variable called y which hase 36 variables. i wrote nvars as 1332. after i write it 1332 it gives that error. Before i introduced the second variable i did not get any erorrs like that before.

I will attach the file. if you cna have look i would be happy.

Answer 2

[Alan Weiss]

You are mixing up the two approaches, problem-based and solver-based. You cannot do that. You have x and y defined as optimization variables. That is fine. You cannot call ga on a problem with optimization variables; you have to call solve.

Also, I am not familiar with prob2matrices. Did you mean prob2struct? In any case, I think that you should stick with the problem-based approach in order to keep the variables x and y separated, not shoved together into one long, hard-to-understand variable.

Alan Weiss

MATLAB mathematical toolbox documentation

[Azime Beyza Ari]

i have used prob2matrices to create my constraints.

https://www.mathworks.com/matlabcentral/fileexchange/74481-prob2matrices-a-selective-version-of-prob2struct

What i am doing which causes conflict? Is there any way without making it hard-to-understand?

Ps. I also wanna solve my problem with ga. It is a requirement.

[Azime Beyza Ari]

Instead of using prob2matrices, if i write my constraints like following, would the error go away (Also since x's all have the same name and there are 1296 of them it think i would be very hard for me to write them in this way) ? or are there any other problems causing it? ;

https://www.mathworks.com/help/optim/ug/example-linear-programming.html