@Override
	public String toString() {
		return
			"+---------------------------------------------------------------------------+\n" +
			"|  Time statistics                                                          |\n" +
			"+---------------------------------------------------------------------------+\n" +
			format(cpattern, "Selection:", d(_selectionDuration)) +
			format(cpattern, "Altering:", d(_alterDuration)) +
			format(cpattern, "Fitness calculation:", d(_evaluationDuration)) +
			format(cpattern, "Overall execution:", d(_evolveDuration)) +
			"+---------------------------------------------------------------------------+\n" +
			"|  Evolution statistics                                                     |\n" +
			"+---------------------------------------------------------------------------+\n" +
			format(cpattern, "Generations:", i(_altered.count())) +
			format(cpattern, "Altered:", i(_altered)) +
			format(cpattern, "Killed:", i(_killed)) +
			format(cpattern, "Invalids:", i(_invalids));
	}
Return the minimal and maximal fitness.

@return minimal and maximal fitness
jenetics/src/main/java/io/jenetics/engine/EvolutionStatistics.java