function engine = distribute_evidence(engine, root)if isempty(engine.preorder{root})  % this is the first time we have distributed from this root  % memoize the order  [jtree, preorder, postorder] = mk_rooted_tree(engine.jtree, root);  preorder_children = cell(1,length(preorder));  for n=preorder    preorder_children{n} = children(jtree, n);  end  engine.preorder{root} = preorder;  engine.preorder_children{root} = preorder_children;else  preorder = engine.preorder{root};  preorder_children = engine.preorder_children{root};end% distribute from root (node to children)for n=preorder(:)'  for c=preorder_children{n}(:)'    engine.clpot{c} = divide_by_pot(engine.clpot{c}, engine.seppot{n,c});     engine.seppot{n,c} = marginalize_pot(engine.clpot{n}, engine.separator{n,c}, engine.maximize);    engine.clpot{c} = multiply_by_pot(engine.clpot{c}, engine.seppot{n,c});  endend