# Source code for rl_coach.filters.reward.reward_rescale_filter

    #
    # Copyright (c) 2017 Intel Corporation
    #
    # Licensed under the Apache License, Version 2.0 (the "License");
    # you may not use this file except in compliance with the License.
    # You may obtain a copy of the License at
    #
    #      http://www.apache.org/licenses/LICENSE-2.0
    #
    # Unless required by applicable law or agreed to in writing, software
    # distributed under the License is distributed on an "AS IS" BASIS,
    # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    # See the License for the specific language governing permissions and
    # limitations under the License.
    #

    from rl_coach.core_types import RewardType
    from rl_coach.filters.reward.reward_filter import RewardFilter
    from rl_coach.spaces import RewardSpace

    class RewardRescaleFilter(RewardFilter):
        """
        Rescales the reward by a given factor. Rescaling the rewards of the environment has been
        observed to have a large effect (negative or positive) on the behavior of the learning process.
        """
        def __init__(self, rescale_factor: float):
            """
            :param rescale_factor: The reward rescaling factor by which the reward will be multiplied
            """
            super().__init__()
            self.rescale_factor = rescale_factor

            if rescale_factor == 0:
                raise ValueError("The reward rescale value can not be set to 0")

        def filter(self, reward: RewardType, update_internal_state: bool=True) -> RewardType:
            reward = float(reward) * self.rescale_factor
            return reward

        def get_filtered_reward_space(self, input_reward_space: RewardSpace) -> RewardSpace:
            input_reward_space.high = input_reward_space.high * self.rescale_factor
            input_reward_space.low = input_reward_space.low * self.rescale_factor
            return input_reward_space