def _getReward(self):
		reward = self.game.getScore() - self.previous_score
		self.previous_score = self.game.getScore()

		return reward
Replaces population using the non-dominated sorting technique from NSGA-II.
dataset/ETHPy150Open ntasfi/PyGame-Learning-Environment/ple/ple.py/PLE._getReward--crossover with--dataset/ETHPy150Open aarongarrett/inspyred/inspyred/ec/replacers.py/nsga_replacement