Can anybody please explain this objective function alongwith the ga code??

function [y] = obj_function(x,N,compen_len,data_sample,CP_p1_start,CP_p1_end,CP_p2_start,CP_p2_end)
    y = zeros(1,1); 
    data_sample(1,CP_p1_start:CP_p1_end) = x(1:compen_len);
    data_sample(1,CP_p2_start:CP_p2_end) = x(compen_len + 1:end);
    data_expnd = [zeros(1,N), ifft(data_sample,N), zeros(1,N)];
    nfft = 2^nextpow2(length(data_expnd));
    Pxx = abs(fft(data_expnd,nfft)).^2;
    Pxx = Pxx(1,1:nfft/2);
    expan_fact = nfft/N;
    crop_start = (CP_p1_start + compen_len)*expan_fact;
    crop_end = (CP_p2_end - compen_len)*expan_fact;
N = 1024;
 compen_len = 12;
CP_p1_start = LU_start_sub_carr - compen_len ;
CP_p2_end = LU_end_sub_carr + compen_len ;
CP_p1_end = CP_p1_start + compen_len - 1;
CP_p2_start = CP_p2_end - compen_len + 1;

      y(1) = mean(abs(Pxx(crop_start:crop_end))); 
  %     y(2) = EC;
  %     y(3) = Fl;
  %     y(4) = Pe;
  end

function [x,fval] = call_genetic(init_pop,max_gen,time_limit,N,data_sample,compen_len,CP_p1_start,CP_p1_end,CP_p2_start,CP_p2_end)
    nvars = 2*compen_len;
    options = gaoptimset(@gamultiobj);
    options = gaoptimset(options,'Generations',max_gen,'FitnessLimit',0,'TolFun',1e-3,'TimeLimit',time_limit,'Display','iter','PopulationSize',init_pop,'PlotFcns',{@gaplotscorediversity});
    LB = -10*ones(1,nvars);
    UB = 10*ones(1,nvars);
    [x,fval] = gamultiobj(@(x)obj_function(x,N,compen_len,data_sample,CP_p1_start,CP_p1_end,CP_p2_start,CP_p2_end),nvars,[],[],[],[],LB,UB,options);
end

[Walter Roberson]

Duplicate merged into original http://uk.mathworks.com/matlabcentral/answers/267068-can-someone-pls-explain-this-ga-function