# suggest a method/algorithm to solve Combinatorial optimization

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ANUBHAV Goel on 17 Dec 2020
Commented: ANUBHAV Goel on 21 Dec 2020
I have three different set of variables
SC=[a,b,c,d,e,f]; % each option a, b, etc are actually temperature dependent and can be evaluated using empirical correaltions
AM=[p;q;r]; % each option p,q, etc are actually temp dependent and can be evaluated using empirical correaltions
HF=[m,n,x,y,z]; % each option m,n, etc are actually temp dependent and can be evaluated using empirical correaltions
, need to choose a best combination by picking one option from each set such that the resulting combination maximizes the efficiency
efficiency is the evaluated by putting value of these variables in a mathematical model.
Which opimization technique/algorithm can solve such problem.
Thanks a lot.
Bruno Luong on 19 Dec 2020
There are 6*3*5 = 90 combinations, can't you just evaluate them all then pick the best?

Ameer Hamza on 17 Dec 2020
Edited: Ameer Hamza on 17 Dec 2020
I don't think there is a function in MATLAB that operate on a list of optimization variables. The closest possible option is to use the optimizer to generate the index of these variables. Only ga() and surrogateopt() will work for nonlinear integer optimization.
For example, consider this
SC = [1 2 3 4 5 6];
AM = [1 2 3];
HF = [5 4 3 2 1];
lb = [1 1 1];
ub = [6 3 5]; % upper bound for indexes
sol = ga(@(x) objFun(x, SC, AM, HF), 3, [], [], [], [], lb, ub, [], 1:3)
SC_sol = SC(sol(1))
AM_sol = AM(sol(2))
HF_sol = HF(sol(3))
function y = objFun(ind, SC, AM, HF)
y = myModel(SC(ind(1)), AM(ind(2)), HF(ind(3)));
end
function y = myModel(sc, am, hf)
y = sc + am + hf;
end
However, I guess surrogateopt() is more appropriate here, since it is explicitly defined for "time-consuing objective function"
SC = [1 2 3 4 5 6];
AM = [1 2 3];
HF = [5 4 3 2 1];
lb = [1 1 1];
ub = [6 3 5]; % upper bound for indexes
opts = optimoptions('surrogateopt', 'PlotFcn', '');
sol = surrogateopt(@(x) objFun(x, SC, AM, HF),lb, ub, 1:3, opts)
SC_sol = SC(sol(1))
AM_sol = AM(sol(2))
HF_sol = HF(sol(3))
function y = objFun(ind, SC, AM, HF)
y = myModel(SC(ind(1)), AM(ind(2)), HF(ind(3)));
end
function y = myModel(sc, am, hf)
y = sc + am + hf;
end
ANUBHAV Goel on 21 Dec 2020
Thanks a lot for sharing knowledge and your time..