fmincon output is converging to infeasible point

I am getting an output that is correctly following lower bound and upper bound but is not satisfying the non-linear constraint. Those values are not useful for me at all. Do let me know if you require the entire code.

m = 20
lb = zeros(m,2);
ub = ones(m,2);
Y = 0.5.*ub;

[xopt,fval] = fmincon(@getCost,Y,[],[],[],[],lb,ub,@nlcon)


function [x,n,N,S] = getCost(Y)
..............
    .........
end

%Constraint function
function [c, ceq] = nlcon(Y)
[~,~,c,~] = getCost(Y);
[~,~,~,ceq] = getCost(Y);
c = ceq;
end

Answer 1

[Alan Weiss]

While I don't understand your listed code at all, perhaps you will be able to solve your problem using some ideas from the documentaton on what to do when the solver converges to an infeasible point.

Alan Weiss

MATLAB mathematical toolbox documentation

[Harshvardhan Tandon]

I did try what you recommended but fmincon was still converging to an infeasible point. My program is quite complex to be solved easily. I am trying to use different/ or modify the non-linear constraints and get convergence to a feasible point.

%Constraint function
function [c, ceq] = nlcon(Y)
[~,~,c,~] = getCost(Y);
[~,~,~,ceq] = getCost(Y);
c = ceq;
end
                      %%%I made it to this%%%
%Constraint function
function [c, ceq] = nlcon(Y)
[~,~,c,~] = getCost(Y);
[~,~,~,ceq] = getCost(Y);
c == ceq;
end

If you could give an idea of how fmincon reaches its value or how it reacts to when i put a '==' operator. That would be helpful.

[Alan Weiss]

As I said, I don't understand your code at all, so I don't know what you are trying to do or how to advise you. In particular, I don't know what you are attempting to do with the 'c = ceq' or 'c == ceq' calls. To me, they are equally nonsensical, but I'm sure that you have a reason for including them. I would have simply given

function [c, ceq] = nlcon(Y)
[~,~,c,ceq] = getCost(Y);
end

but I don't know what any of these lines of code mean.

I suggest that you try using the debugger to see what MATLAB is doing.

Alan Weiss

MATLAB mathematical toolbox documentation