function [gt, npos] = labeldata(cls, dataset)

% Load and cache ground-truth annontation data for fast
% resuse when running context rescoring experiments.
% Some of this code is borrowed from the PASCAL devkit.

globals;
pascal_init;

try
  load([cachedir cls '_labeldata_' dataset '_' VOCyear]);
catch
  % load ground truth objects
  [gtids,t] = textread(sprintf(VOCopts.imgsetpath,dataset),'%s %d');  
  tic;
  npos=0;
  for i=1:length(gtids)
    % display progress
    if toc>1
      fprintf('%s: rescore labels: load: %d/%d\n',cls,i,length(gtids));
      drawnow;
      tic;
    end

    % read annotation
    rec=PASreadrecord(sprintf(VOCopts.annopath,gtids{i}));

    % extract objects of class
    clsinds=strmatch(cls,{rec.objects(:).class},'exact');
    gt(i).BB=cat(1,rec.objects(clsinds).bbox)';
    gt(i).diff=[rec.objects(clsinds).difficult];
    gt(i).det=false(length(clsinds),1);
    npos=npos+sum(~gt(i).diff);
  end
  save([cachedir cls '_labeldata_' dataset '_' VOCyear], 'gt', 'npos');
end