Documentation>vl_demo_kmeans_ann_speed

# Source code for ``vl_demo_kmeans_ann_speed.m

This file is located in the ``toolbox/demo folder in VLFeat package.

    % VL_DEMO_KMEANS_ANN_SPEED   Compares Lloyd's, Elkan, and ANN k-means

    numCenters = 200 ;
    numTrials = 3 ;
    maxNumIterations = 10 ;
    initialization = 'randsel' ;
    %initialization = 'plusplus';
    distance = 'l2' ;

    %% Create an example dataset

    dimension = 32 ;
    numData = 50000 ;

    X = randn(dimension,numData);

    %% Run various k-means algorithms on the data
    algorithms = {'Lloyd','Elkan','ANN 1/4','ANN 1/10','ANN 1/50' } ;
    options = {{'Algorithm', 'Lloyd'}, ...
               {'Algorithm', 'Elkan'}, ...
               {'Algorithm', 'ANN', 'MaxNumComparisons', ceil(numCenters / 4)}, ...
               {'Algorithm', 'ANN', 'MaxNumComparisons', ceil(numCenters / 10)}, ...
               {'Algorithm', 'ANN', 'MaxNumComparisons', ceil(numCenters / 50)}} ;
    numCpus = [1 0] ;

    clear time energy ;
    for n = 1:2
      for a = 1:numel(algorithms)
        for t = 1:numTrials
          vl_threads(numCpus(n)) ;
          start = tic ;
          [C, A, E] = vl_kmeans(X, ...
                                numCenters, 'Verbose', ...
                                'Distance', distance, ...
                                'MaxNumIterations', maxNumIterations, ...
                                options{a}{:}) ;
          if vl_isoctave()
            time(t,a,n) = (tic() - start) / 1e6 ;
          else
            time(t,a,n) = toc(start) ;
          end
          energy(t,a,n) = E ;
        end
      end
    end

    % average over tirals
    time = squeeze(mean(time,1)) ;
    energy = squeeze(mean(energy,1)) ;

    figure(1) ; clf ;
    for n=1:2
      if n == 1
        str = 'Serial' ;
      else
        str = 'Parallel' ;
      end

      subplot(3,2,(n-1)+1) ;
      bar(time(:,n)) ;
      set(gca,'XTickLabel',algorithms);
      set(gca,'FontSize',8),
      xlabel('Algorithm');
      ylabel('Time [s]');
      title(str) ;

      subplot(3,2,(n-1)+3) ;
      bar(energy(:,n));
      set(gca,'XTickLabel',algorithms);
      set(gca,'FontSize',8),
      xlabel('Algorithm');
      ylabel('Energy');
      title(str) ;

      subplot(3,2,(n-1)+5) ;
      bar(time(1,1)./time(:,n)) ;
      set(gca,'XTickLabel',algorithms);
      set(gca,'FontSize',8),
      xlabel('Algorithm');
      ylabel('Speedup');
      title(str) ;
    end

    vl_demo_print('kmeans_speed',1);