function jt = globalpropagation( jtree, ns )
% step 1.
X = jtree{1}{1};
% step 2.
jtree = unmark_cliques( jtree );
jtree = collect_evidence( X, jtree, [], ns );
% step 3.
jtree = unmark_cliques( jtree );
jtree = distribute_evidence( X, jtree, [], ns );
jt = jtree;