%%**********************************************************************
%% blktrace: compute <X1,Z1> + ... <Xp,Zp>
%%              
%% SDPT3: version 3.1
%% Copyright (c) 1997 by
%% K.C. Toh, M.J. Todd, R.H. Tutuncu
%% Last Modified: 16 Sep 2004
%%**********************************************************************

  function trXZ = blktrace(blk,X,Z,parbarrier); 

  if (nargin == 3); 
     trXZ = 0; 
     for p = 1:size(blk,1)
        pblk = blk(p,:);
        if strcmp(pblk{1},'s')
           trXZ = trXZ + sum(sum(X{p}.*Z{p})); 
        else
           trXZ = trXZ + sum(X{p}.*Z{p}); 
        end
     end
  elseif (nargin == 4)
     trXZ = 0; 
     for p = 1:size(blk,1)
        pblk = blk(p,:);
        idx = find(parbarrier{p} == 0); 
        if ~isempty(idx)             
           if strcmp(pblk{1},'s')
              sumXZ = sum(X{p}.*Z{p}); 
              ss = [0,cumsum(pblk{2})];
              for k = 1:length(idx)
                 idxtmp = [ss(idx(k))+1:ss(idx(k)+1)];
                 trXZ = trXZ + sum(sumXZ(idxtmp)); 
              end
           elseif strcmp(pblk{1},'q')
	      tmp = qops(pblk,X{p},Z{p},1);
              trXZ = trXZ + sum(tmp(idx));
           elseif strcmp(pblk{1},'l')
              trXZ = trXZ + sum(X{p}(idx).*Z{p}(idx)); 
           end
        end
     end
  end
%%**********************************************************************