nn.py

# -*- coding: utf-8 -*-
# Copyright 2019 - present, Facebook, Inc
#
# 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.
# ---------------------------------------------------------------------
# MegEngine is Licensed under the Apache License, Version 2.0 (the "License")
#
# Copyright (c) 2014-2020 Megvii Inc. All rights reserved.
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#
# This file has been modified by Megvii ("Megvii Modifications").
# All Megvii Modifications are Copyright (C) 2014-2019 Megvii Inc. All rights reserved.
# ---------------------------------------------------------------------
from collections import namedtuple

import megengine.module as M


class Conv2d(M.Conv2d):
    """
    A wrapper around :class:`megengine.module.Conv2d`.
    """

    def __init__(self, *args, **kwargs):
        """
        Extra keyword arguments supported in addition to
        `megengine.module.Conv2d`.

        Args:
            norm (M.Module, optional): a normalization layer
            activation (callable(Tensor) -> Tensor): a callable activation
                function
        """
        norm = kwargs.pop("norm", None)
        activation = kwargs.pop("activation", None)
        super().__init__(*args, **kwargs)

        self.norm = norm
        self.activation = activation

    def forward(self, x):
        x = super().forward(x)
        if self.norm is not None:
            x = self.norm(x)
        if self.activation is not None:
            x = self.activation(x)
        return x


class ShapeSpec(namedtuple("_ShapeSpec", ["channels", "height", "width", "stride"])):
    """
    A simple structure that contains basic shape specification about a tensor.
    Useful for getting the modules output channels when building the graph.
    """

    def __new__(cls, channels=None, height=None, width=None, stride=None):
        return super().__new__(cls, channels, height, width, stride)