private static IndexPermutator getPermutator(boolean usePermutator,
			int length) {
		IndexPermutator permutator;
		if (usePermutator) {
			permutator = new ExactIndexPermutator(length);
			permutator = new RevertIndexPermutator(permutator);
		} else {
			permutator = new ShuffleIndexPermutator(length);
		}
		return permutator;
	}