function svecs=svmExtractSupportVectors(model_file)
% returns the support vector ids
fd = fopen(model_file,'r');
fltingpt = '[-+]?[0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?';
ptrn = ['^(' fltingpt ')(\s+\d+:' fltingpt ')+?\s*#(.*?)\s*$'];
svecs=[];
ii=1;
while 1
   tline = fgetl(fd);
   if ~ischar(tline), break, end
   match=regexp(tline,ptrn,'tokens');
   if length(match)==1 && length(match{1})==3
	   %svecs(end+1) = str2num(match{1}{3});
	   %fprintf('%d %s\n',ii,str2num(match{1}{3})); ii=ii+1;
	   svecs(end+1) = ii; ii=ii+1;
   end
end
fclose(fd);
svecs = sort(svecs);