Question

I am running into a puzzling error when when using the ga function in MATLAB’s global optimization toolbox, the error message is pasted below to see if anyone can decipher what this means.

I am trying to seed the ga with an initial population, a matrix of pop-by-nvar. However, this produces the error below. I can only get the ga to run if I pass in an initial population vector of (pop-1)-by-nvar. This is a little inconvenient since I want to specify the entire population. I hope someone who is familiar with the global optimization toolbox and the ga function can shed some light here!

??? Index exceeds matrix dimensions.

Error in ==> gacreationlinearfeasible>lhsLambda at 213
    [lambda(i,:),f,e] = fmincon(fun,lambda(i,:),[],[],Aeq,beq,lb,ub,[],opts);

Error in ==> gacreationlinearfeasible>feasibleLHS at 180
            initialPopulation(boundary_points+1:interior_points+boundary_points,:) = ...

Error in ==> gacreationlinearfeasible at 42
        feasiblePop = feasibleLHS(individualsToCreate,GenomeLength,options);

Error in ==> makeState at 30
      state.Population = feval(options.CreationFcn,GenomeLength,FitnessFcn,options,options.CreationFcnArgs{:});

Error in ==> galincon at 18
state = makeState(GenomeLength,FitnessFcn,Iterate,output.problemtype,options);

Error in ==> ga at 282
        [x,fval,exitFlag,output,population,scores] = galincon(FitnessFcn,nvars, ...

Answer 1

Here is an example of using GA with specifying an initial population:

%# find minima
initPop = bsxfun(@plus, [2 3], randn(20,2)*2);    %# 20-by-2 matrix
opts = gaoptimset('InitialPopulation',initPop);
[x, fx, flag, out, pop] = ga(@rastriginsfcn, 2, [],[], [],[], [],[], [], opts);

%# plot solution
figure('Renderer','opengl')
ezsurfc(@(x,y) rastriginsfcn([x,y])), colormap hot
line(x(1), x(2), fx, 'Marker','.', 'MarkerSize',50, 'Color','b')
view(3)

Here is the solution I get after 72 generations:

Note that the Rastrigin function has the global minimum at (0,0)