PaddleClas：自定义backbone

PaddleClas提供的都是现成的网络结构和权重，不一定适用，所以有必要掌握魔改的技能。

PaddleClas版本：2.5

1：新建 mynet.py

• 在 ppcls/arch/backbone/model_zoo/ 文件夹下新建一个自己的模型结构文件 mynet.py，即你自己的 backbone;

2：模型搭建

• 在mynet.py中搭建自己的网络，可以参考model_zoo或legendary_models中的众多模型文件;

#我以legendary_models/mobilenet_v3.py为参考，添加激活函数FReLU

# copyright (c) 2021 PaddlePaddle Authors. All Rights Reserve.
#
# 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.

# reference: https://arxiv.org/abs/1905.02244

from __future__ import absolute_import, division, print_function

import paddle
import paddle.nn as nn
from paddle import ParamAttr
from paddle.nn import AdaptiveAvgPool2D, BatchNorm, Conv2D, Dropout, Linear
from paddle.regularizer import L2Decay

from ..base.theseus_layer import TheseusLayer
from ....utils.save_load import load_dygraph_pretrain, load_dygraph_pretrain_from_url

MODEL_URLS = {
    "MobileNetV3_large_FRELU":""
}

MODEL_STAGES_PATTERN = {
    "MobileNetV3_large_FRELU":
    ["blocks[0]", "blocks[2]", "blocks[5]", "blocks[11]", "blocks[14]"]
}

__all__ = MODEL_URLS.keys()

# "large", "small" is just for MobinetV3_large, MobileNetV3_small respectively.
# The type of "large" or "small" config is a list. Each element(list) represents a depthwise block, which is composed of k, exp, se, act, s.
# k: kernel_size
# exp: middle channel number in depthwise block
# c: output channel number in depthwise block
# se: whether to use SE block
# act: which activation to use
# s: stride in depthwise block
NET_CONFIG = {
    "large": [
        # k, exp, c, se, act, s
        [3, 16, 16, False, "frelu", 1],#[3, 16, 16, False, "relu", 1],
        [3, 64, 24, False, "frelu", 2],
        [3, 72, 24, False, "frelu", 1],
        [5, 72, 40, True, "frelu", 2],
        [5, 120, 40, True, "frelu", 1],
        [5, 120, 40, True, "frelu", 1],
        [3, 240, 80, False, "hardswish", 2],
        [3, 200, 80, False, "hardswish", 1],
        [3, 184, 80, False, "hardswish", 1],
        [3, 184, 80, False, "hardswish", 1],
        [3, 480, 112, True, "hardswish", 1],
        [3, 672, 112, True, "hardswish", 1],
        [5, 672, 160, True, "hardswish", 2],
        [5, 960, 160, True, "hardswish", 1],
        [5, 960, 160, True, "hardswish", 1],
    ]
}
# first conv output channel number in MobileNetV3
STEM_CONV_NUMBER = 16
# last second conv output channel for "large"
LAST_SECOND_CONV_LARGE = 960
# last conv output channel number for "large"
LAST_CONV = 1280


class FReLU(nn.Layer):
    def __init__(self, dim, init_weight=False):
        super().__init__()
        self.conv = nn.Conv2D(dim, dim, 3, 1, 1, groups=dim)
        self.bn = nn.BatchNorm2D(dim)
        if init_weight:
            self.apply(self._init_weight)

    def _init_weight(self, m):
        init = nn.initializer.Normal(mean=0, std=.01)
        zeros = nn.initializer.Constant(0.)
        ones = nn.initializer.Constant(1.)
        if isinstance(m, nn.Conv2D):
            init(m.weight)
            zeros(m.bias)
        if isinstance(m, nn.BatchNorm2D):
            ones(m.weight)
            zeros(m.bias)
            

    def forward(self, x):
        x1 = self.bn(self.conv(x))
        out = paddle.maximum(x, x1)
        return out


def _make_divisible(v, divisor=8, min_value=None):
    if min_value is None:
        min_value = divisor
    new_v = max(min_value, int(v + divisor / 2) // divisor * divisor)
    if new_v < 0.9 * v:
        new_v += divisor
    return new_v


def _create_act(act, dim):
    if act == "hardswish":
        return nn.Hardswish()
    elif act == "relu":
        return nn.ReLU()
    elif act == "frelu":
        return FReLU(dim)
    elif act is None:
        return None
    else:
        raise RuntimeError(
            "The activation function is not supported: {}".format(act))


class MobileNetV3_FReLU(TheseusLayer):
    """
    MobileNetV3_FReLU
    Args:
        config: list. MobileNetV3 depthwise blocks config.
        scale: float=1.0. The coefficient that controls the size of network parameters. 
        class_num: int=1000. The number of classes.
        inplanes: int=16. The output channel number of first convolution layer.
        class_squeeze: int=960. The output channel number of penultimate convolution layer. 
        class_expand: int=1280. The output channel number of last convolution layer. 
        dropout_prob: float=0.2.  Probability of setting units to zero.
    Returns:
        model: nn.Layer. Specific MobileNetV3 model depends on args.
    """

    def __init__(self,
                 config,
                 stages_pattern,
                 scale=1.0,
                 class_num=1000,
                 inplanes=STEM_CONV_NUMBER,
                 class_squeeze=LAST_SECOND_CONV_LARGE,
                 class_expand=LAST_CONV,
                 dropout_prob=0.2,
                 return_patterns=None,
                 return_stages=None,
                 **kwargs):
        super().__init__()

        self.cfg = config
        self.scale = scale
        self.inplanes = inplanes
        self.class_squeeze = class_squeeze
        self.class_expand = class_expand
        self.class_num = class_num

        self.conv = ConvBNLayer(
            in_c=3,
            out_c=_make_divisible(self.inplanes * self.scale),
            filter_size=3,
            stride=2,
            padding=1,
            num_groups=1,
            if_act=True,
            act="frelu")

        self.blocks = nn.Sequential(* [
            ResidualUnit(
                in_c=_make_divisible(self.inplanes * self.scale if i == 0 else
                                     self.cfg[i - 1][2] * self.scale),
                mid_c=_make_divisible(self.scale * exp),
                out_c=_make_divisible(self.scale * c),
                filter_size=k,
                stride=s,
                use_se=se,
                act=act) for i, (k, exp, c, se, act, s) in enumerate(self.cfg)
        ])

        self.last_second_conv = ConvBNLayer(
            in_c=_make_divisible(self.cfg[-1][2] * self.scale),
            out_c=_make_divisible(self.scale * self.class_squeeze),
            filter_size=1,
            stride=1,
            padding=0,
            num_groups=1,
            if_act=True,
            act="hardswish")

        self.avg_pool = AdaptiveAvgPool2D(1)

        self.last_conv = Conv2D(
            in_channels=_make_divisible(self.scale * self.class_squeeze),
            out_channels=self.class_expand,
            kernel_size=1,
            stride=1,
            padding=0,
            bias_attr=False)

        self.hardswish = nn.Hardswish()
        if dropout_prob is not None:
            self.dropout = Dropout(p=dropout_prob, mode="downscale_in_infer")
        else:
            self.dropout = None
        self.flatten = nn.Flatten(start_axis=1, stop_axis=-1)

        self.fc = Linear(self.class_expand, class_num)

        super().init_res(
            stages_pattern,
            return_patterns=return_patterns,
            return_stages=return_stages)

    def forward(self, x):
        x = self.conv(x)
        x = self.blocks(x)
        x = self.last_second_conv(x)
        x = self.avg_pool(x)
        x = self.last_conv(x)
        x = self.hardswish(x)
        if self.dropout is not None:
            x = self.dropout(x)
        x = self.flatten(x)
        x = self.fc(x)

        return x


class ConvBNLayer(TheseusLayer):
    def __init__(self,
                 in_c,
                 out_c,
                 filter_size,
                 stride,
                 padding,
                 num_groups=1,
                 if_act=True,
                 act=None):
        super().__init__()

        self.conv = Conv2D(
            in_channels=in_c,
            out_channels=out_c,
            kernel_size=filter_size,
            stride=stride,
            padding=padding,
            groups=num_groups,
            bias_attr=False)
        self.bn = BatchNorm(
            num_channels=out_c,
            act=None,
            param_attr=ParamAttr(regularizer=L2Decay(0.0)),
            bias_attr=ParamAttr(regularizer=L2Decay(0.0)))
        self.if_act = if_act
        self.act = _create_act(act,out_c)

    def forward(self, x):
        x = self.conv(x)
        x = self.bn(x)
        if self.if_act:
            x = self.act(x)
        return x


class ResidualUnit(TheseusLayer):
    def __init__(self,
                 in_c,
                 mid_c,
                 out_c,
                 filter_size,
                 stride,
                 use_se,
                 act=None):
        super().__init__()
        self.if_shortcut = stride == 1 and in_c == out_c
        self.if_se = use_se

        self.expand_conv = ConvBNLayer(
            in_c=in_c,
            out_c=mid_c,
            filter_size=1,
            stride=1,
            padding=0,
            if_act=True,
            act=act)
        self.bottleneck_conv = ConvBNLayer(
            in_c=mid_c,
            out_c=mid_c,
            filter_size=filter_size,
            stride=stride,
            padding=int((filter_size - 1) // 2),
            num_groups=mid_c,
            if_act=True,
            act=act)
        if self.if_se:
            self.mid_se = SEModule(mid_c)
        self.linear_conv = ConvBNLayer(
            in_c=mid_c,
            out_c=out_c,
            filter_size=1,
            stride=1,
            padding=0,
            if_act=False,
            act=None)

    def forward(self, x):
        identity = x
        x = self.expand_conv(x)
        x = self.bottleneck_conv(x)
        if self.if_se:
            x = self.mid_se(x)
        x = self.linear_conv(x)
        if self.if_shortcut:
            x = paddle.add(identity, x)
        return x


# nn.Hardsigmoid can't transfer "slope" and "offset" in nn.functional.hardsigmoid
class Hardsigmoid(TheseusLayer):
    def __init__(self, slope=0.2, offset=0.5):
        super().__init__()
        self.slope = slope
        self.offset = offset

    def forward(self, x):
        return nn.functional.hardsigmoid(
            x, slope=self.slope, offset=self.offset)


class SEModule(TheseusLayer):
    def __init__(self, channel, reduction=4):
        super().__init__()
        self.avg_pool = AdaptiveAvgPool2D(1)
        self.conv1 = Conv2D(
            in_channels=channel,
            out_channels=channel // reduction,
            kernel_size=1,
            stride=1,
            padding=0)
        self.relu = nn.ReLU()
        self.conv2 = Conv2D(
            in_channels=channel // reduction,
            out_channels=channel,
            kernel_size=1,
            stride=1,
            padding=0)
        self.hardsigmoid = Hardsigmoid(slope=0.2, offset=0.5)

    def forward(self, x):
        identity = x
        x = self.avg_pool(x)
        x = self.conv1(x)
        x = self.relu(x)
        x = self.conv2(x)
        x = self.hardsigmoid(x)
        return paddle.multiply(x=identity, y=x)


def _load_pretrained(pretrained, model, model_url, use_ssld):
    if pretrained is False:
        pass
    else:
        raise RuntimeError(
            "pretrained type is not available. Please use `string` or `boolean` type."
        )


def MobileNetV3_large_FRelu(pretrained=False, use_ssld=False, **kwargs):
    """
    MobileNetV3_large_x1_0
    Args:
        pretrained: bool=False or str. If `True` load pretrained parameters, `False` otherwise.
                    If str, means the path of the pretrained model.
        use_ssld: bool=False. Whether using distillation pretrained model when pretrained=True.
    Returns:
        model: nn.Layer. Specific `MobileNetV3_large_x1_0` model depends on args.
    """
    model = MobileNetV3_FReLU(
        config=NET_CONFIG["large"],
        scale=1.0,
        stages_pattern=MODEL_STAGES_PATTERN["MobileNetV3_large_FRELU"],
        class_squeeze=LAST_SECOND_CONV_LARGE,
        **kwargs)
    _load_pretrained(pretrained, model, MODEL_URLS["MobileNetV3_large_FRELU"],
                     use_ssld)
    return model

3：声明自己的模型

• 在 ppcls/arch/backbone/__init__.py 中添加自己设计的 backbone 的类;

 4：配置训练yaml文件

• 参考 ppcls/configs/ImageNet/MobileNetV3/MobileNetV3_small_x1_0.yaml;

具体如下：根据自己的数据进行类别数目、数据位置的调整 

# global configs
Global:
  checkpoints: null
  pretrained_model: null
  output_dir: ./output/
  device: gpu
  save_interval: 1
  eval_during_train: True
  eval_interval: 1
  epochs: 100
  print_batch_step: 10
  use_visualdl: False
  # used for static mode and model export
  image_shape: [3, 224, 224]
  save_inference_dir: ./inference

# model architecture
Arch:
  name: MobileNetV3_large_FRELU
  class_num: 100
 
# loss function config for traing/eval process
Loss:
  Train:
    - CELoss:
        weight: 1.0
  Eval:
    - CELoss:
        weight: 1.0


Optimizer:
  name: Momentum
  momentum: 0.9
  lr:
    name: Cosine
    learning_rate: 0.04
  regularizer:
    name: 'L2'
    coeff: 0.0001


# data loader for train and eval
DataLoader:
  Train:
    dataset:
      name: ImageNetDataset
      image_root: ./dataset/CIFAR100/
      cls_label_path: ./dataset/CIFAR100/train_list.txt
      transform_ops:
        - DecodeImage:
            to_rgb: True
            channel_first: False
        - RandCropImage:
            size: 32
        - RandFlipImage:
            flip_code: 1
        - AutoAugment:
        - NormalizeImage:
            scale: 1.0/255.0
            mean: [0.485, 0.456, 0.406]
            std: [0.229, 0.224, 0.225]
            order: ''

    sampler:
      name: DistributedBatchSampler
      batch_size: 64
      drop_last: False
      shuffle: True
    loader:
      num_workers: 4
      use_shared_memory: True

  Eval:
    dataset: 
      name: ImageNetDataset
      image_root: ./dataset/CIFAR100/
      cls_label_path: ./dataset/CIFAR100/test_list.txt
      transform_ops:
        - DecodeImage:
            to_rgb: True
            channel_first: False
        - ResizeImage:
            resize_short: 36
        - CropImage:
            size: 32
        - NormalizeImage:
            scale: 1.0/255.0
            mean: [0.485, 0.456, 0.406]
            std: [0.229, 0.224, 0.225]
            order: ''
    sampler:
      name: DistributedBatchSampler
      batch_size: 64
      drop_last: False
      shuffle: False
    loader:
      num_workers: 4
      use_shared_memory: True

Infer:
  infer_imgs: docs/images/inference_deployment/whl_demo.jpg
  batch_size: 10
  transforms:
    - DecodeImage:
        to_rgb: True
        channel_first: False
    - ResizeImage:
        resize_short: 36
    - CropImage:
        size: 32
    - NormalizeImage:
        scale: 1.0/255.0
        mean: [0.485, 0.456, 0.406]
        std: [0.229, 0.224, 0.225]
        order: ''
    - ToCHWImage:
  PostProcess:
    name: Topk
    topk: 5
    class_id_map_file: ppcls/utils/imagenet1k_label_list.txt

Metric:
  Train:
    - TopkAcc:
        topk: [1, 5]
  Eval:
    - TopkAcc:
        topk: [1, 5]

 5：启动训练

python3 -m paddle.distributed.launch \
    --gpus="0" \
    tools/train.py \
        -c ./ppcls/configs/ImageNet/MobileNetV3/MobileNetV3_large_FRELU.yaml  \
        -o Global.output_dir="./output/output_CIFAR_mbv3_FRELU" \
        -o Optimizer.lr.learning_rate=0.01
         

顺利跑完，在cifar100数据上，有轻微的提升。

 

FRELU作者对MBV3的提升，也做了解释：

 

参考：

https://github.com/PaddlePaddle/PaddleClas/blob/release/2.5/docs/zh_CN/FAQ/faq_2020_s1.md#1