ITE / code / IPA / optimization / clustering_UD0_greedy_additive_wrt_subspaces.m

function [per] = clustering_UD0_greedy_additive_wrt_subspaces(s_ICA,ds,cost_type,co)
%Clusters the ICA (s_ICA) elements to subspaces of given dimensions (ds)
%using (i) 'greedy' clustering and (ii) a cost which is additive with respect 
%to the subspaces (see cost_type = 'sumH', 'sum-I').
%
%INPUT:
% s_ICA: s_ICA(:,t) is the t^th estimated realization of the ICA sources.
%    ds: subspace dimensions.
%    co: is the initialized cost object (entropy/mutual information).
%OUTPUT:
%   per: permutation of the ICA elements.
%
%Copyright (C) 2012 Zoltan Szabo ("http://nipg.inf.elte.hu/szzoli", "szzoli (at) cs (dot) elte (dot) hu")
%
%This file is part of the ITE (Information Theoretical Estimators) Matlab/Octave toolbox.
%
%ITE is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by
%the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
%
%This software is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
%MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
%
%You should have received a copy of the GNU General Public License along with ITE. If not, see <http://www.gnu.org/licenses/>.

%initialization:
    D = sum(ds); %dim(source)
    per = [1:D]; %the actual permutation vector
    cum_ds = cumsum([1;ds(1:end-1)]);%1,d_1+1,d_1+d_2+1,...,d_1+...+d_{M-1}+1 = starting indices of the subspaces (M=number of subspaces).
    %costs:
        [cost_temp,costs] = cost_additive_wrt_subspaces(s_ICA,ds,cost_type,co);%cost_temp:not needed (here)
    it_max = 30; %maximal number of iterations        
    it = 1;      
    
disp('Clustering of the ICA elements (greedy optimization): started.'); 
while (it <= it_max)
    cost_changed = 0;
    %p and q are coordinates belonging to different subspaces; change them if it decreases the cost:
        for p = 1  : D - ds(end)
            ind_of_p_subspace = sum(cum_ds<=p);
            for q =  cum_ds(ind_of_p_subspace+1) : D
                %---------------------
                %start/end indices of the subspaces of p and q:
                    ind_p_start = cum_ds(ind_of_p_subspace);
                    ind_p_end = ind_p_start + ds(ind_of_p_subspace)-1;
                    ind_of_q_subspace = sum(cum_ds<=q);                    
                    ind_q_start = cum_ds(ind_of_q_subspace);
                    ind_q_end = ind_q_start + ds(ind_of_q_subspace)-1;
                 %cost_before,cost_after:
                     cost_before = costs(ind_of_p_subspace) + costs(ind_of_q_subspace);
                     cost_after_p = cost_additive_wrt_subspaces_one_subspace(s_ICA(per([ind_p_start:p-1,q,p+1:ind_p_end]),:),cost_type,co); 
                     cost_after_q = cost_additive_wrt_subspaces_one_subspace(s_ICA(per([ind_q_start:q-1,p,q+1:ind_q_end]),:),cost_type,co);
                     cost_after = cost_after_p + cost_after_q;
                 if cost_after < cost_before%the (p,q) change seems to be useful
                      per([p,q]) = per([q,p]);
                      cost_changed = 1;
                      costs(ind_of_p_subspace) = cost_after_p;
                      costs(ind_of_q_subspace) = cost_after_q;
                 end
                 %---------------------
            end
        end
     disp(strcat(['Iteration ',num2str(it),': ready.']));      
     it = it + 1;%this iteration is coming             
     if (~cost_changed) %<->it is superfluous to iterate more, no coordinate change improves the cost function
        break;
     end
end
    
disp('Clustering of the ICA elements: ready.');
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