Second, while the HTM algorithm uses support to prune the search space (only trees with a minimum support bigger than the set threshold are stored), the ETM algorithm drastically prunes the search space by additionally checking that the suspicion rate of all subtrees contained in a new tree t is smaller or equal to the suspicion rate of t .
while ETM looses the space advantage of HTM by a small margin 4 , it benefits from a much stronger pruning of the search space than HTM through suspicion rate checking.