# Copyright 2021 Sony Corporation.
# Copyright 2021,2022,2023 Sony Group 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 abc import ABCMeta, abstractmethod
from typing import Optional, Tuple
import nnabla as nn
from nnabla_rl.distributions import Distribution
from nnabla_rl.models.model import Model
[docs]class Encoder(Model, metaclass=ABCMeta):
[docs] @abstractmethod
def encode(self, x: nn.Variable, **kwargs) -> nn.Variable:
"""Encode the input variable to latent representation.
Args:
x (nn.Variable): encoder input.
Returns:
nn.Variable: latent variable
"""
raise NotImplementedError
[docs]class VariationalAutoEncoder(Encoder):
[docs] @abstractmethod
def encode_and_decode(self, x: nn.Variable, **kwargs) -> Tuple[Distribution, nn.Variable]:
"""Encode the input variable and reconstruct.
Args:
x (nn.Variable): encoder input.
Returns:
Tuple[Distribution, nn.Variable]: latent distribution and reconstructed input
"""
raise NotImplementedError
[docs] @abstractmethod
def decode(self, z: Optional[nn.Variable], **kwargs) -> nn.Variable:
"""Reconstruct the latent representation.
Args:
z (nn.Variable, optional): latent variable. If the input is None, random sample will be used instead.
Returns:
nn.Variable: reconstructed variable
"""
raise NotImplementedError
[docs] @abstractmethod
def decode_multiple(self, z: Optional[nn.Variable], decode_num: int, **kwargs):
"""Reconstruct multiple latent representations.
Args:
z (nn.Variable, optional): encoder input. If the input is None, random sample will be used instead.
Returns:
nn.Variable: Reconstructed input and latent distribution
"""
raise NotImplementedError
[docs] @abstractmethod
def latent_distribution(self, x: nn.Variable, **kwargs) -> Distribution:
"""Compute the latent distribution :math:`p(z|x)`.
Args:
x (nn.Variable): encoder input.
Returns:
Distribution: latent distribution
"""
raise NotImplementedError