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Paddle/python/paddle/vision/models/resnet.py

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# Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserved.
#
# 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 __future__ import division
from __future__ import print_function
import math
import paddle.fluid as fluid
from paddle.fluid.dygraph.nn import Conv2D, Pool2D, BatchNorm, Linear
from paddle.fluid.dygraph.container import Sequential
from paddle.utils.download import get_weights_path_from_url
__all__ = [
'ResNet', 'resnet18', 'resnet34', 'resnet50', 'resnet101', 'resnet152'
]
model_urls = {
'resnet18': ('https://paddle-hapi.bj.bcebos.com/models/resnet18.pdparams',
'0ba53eea9bc970962d0ef96f7b94057e'),
'resnet34': ('https://paddle-hapi.bj.bcebos.com/models/resnet34.pdparams',
'46bc9f7c3dd2e55b7866285bee91eff3'),
'resnet50': ('https://paddle-hapi.bj.bcebos.com/models/resnet50.pdparams',
'5ce890a9ad386df17cf7fe2313dca0a1'),
'resnet101': ('https://paddle-hapi.bj.bcebos.com/models/resnet101.pdparams',
'fb07a451df331e4b0bb861ed97c3a9b9'),
'resnet152': ('https://paddle-hapi.bj.bcebos.com/models/resnet152.pdparams',
'f9c700f26d3644bb76ad2226ed5f5713'),
}
class ConvBNLayer(fluid.dygraph.Layer):
def __init__(self,
num_channels,
num_filters,
filter_size,
stride=1,
groups=1,
act=None):
super(ConvBNLayer, self).__init__()
self._conv = Conv2D(
num_channels=num_channels,
num_filters=num_filters,
filter_size=filter_size,
stride=stride,
padding=(filter_size - 1) // 2,
groups=groups,
act=None,
bias_attr=False)
self._batch_norm = BatchNorm(num_filters, act=act)
def forward(self, inputs):
x = self._conv(inputs)
x = self._batch_norm(x)
return x
class BasicBlock(fluid.dygraph.Layer):
"""residual block of resnet18 and resnet34
"""
expansion = 1
def __init__(self, num_channels, num_filters, stride, shortcut=True):
super(BasicBlock, self).__init__()
self.conv0 = ConvBNLayer(
num_channels=num_channels,
num_filters=num_filters,
filter_size=3,
act='relu')
self.conv1 = ConvBNLayer(
num_channels=num_filters,
num_filters=num_filters,
filter_size=3,
stride=stride,
act='relu')
if not shortcut:
self.short = ConvBNLayer(
num_channels=num_channels,
num_filters=num_filters,
filter_size=1,
stride=stride)
self.shortcut = shortcut
def forward(self, inputs):
y = self.conv0(inputs)
conv1 = self.conv1(y)
if self.shortcut:
short = inputs
else:
short = self.short(inputs)
y = short + conv1
return fluid.layers.relu(y)
class BottleneckBlock(fluid.dygraph.Layer):
"""residual block of resnet50, resnet101 amd resnet152
"""
expansion = 4
def __init__(self, num_channels, num_filters, stride, shortcut=True):
super(BottleneckBlock, self).__init__()
self.conv0 = ConvBNLayer(
num_channels=num_channels,
num_filters=num_filters,
filter_size=1,
act='relu')
self.conv1 = ConvBNLayer(
num_channels=num_filters,
num_filters=num_filters,
filter_size=3,
stride=stride,
act='relu')
self.conv2 = ConvBNLayer(
num_channels=num_filters,
num_filters=num_filters * self.expansion,
filter_size=1,
act=None)
if not shortcut:
self.short = ConvBNLayer(
num_channels=num_channels,
num_filters=num_filters * self.expansion,
filter_size=1,
stride=stride)
self.shortcut = shortcut
self._num_channels_out = num_filters * self.expansion
def forward(self, inputs):
x = self.conv0(inputs)
conv1 = self.conv1(x)
conv2 = self.conv2(conv1)
if self.shortcut:
short = inputs
else:
short = self.short(inputs)
x = fluid.layers.elementwise_add(x=short, y=conv2)
return fluid.layers.relu(x)
class ResNet(fluid.dygraph.Layer):
"""ResNet model from
`"Deep Residual Learning for Image Recognition" <https://arxiv.org/pdf/1512.03385.pdf>`_
Args:
Block (BasicBlock|BottleneckBlock): block module of model.
depth (int): layers of resnet, default: 50.
num_classes (int): output dim of last fc layer. If num_classes <=0, last fc layer
will not be defined. Default: 1000.
with_pool (bool): use pool before the last fc layer or not. Default: True.
classifier_activation (str): activation for the last fc layer. Default: 'softmax'.
Examples:
.. code-block:: python
from paddle.vision.models import ResNet
from paddle.vision.models.resnet import BottleneckBlock, BasicBlock
resnet50 = ResNet(BottleneckBlock, 50)
resnet18 = ResNet(BasicBlock, 18)
"""
def __init__(self,
Block,
depth=50,
num_classes=1000,
with_pool=True,
classifier_activation='softmax'):
super(ResNet, self).__init__()
self.num_classes = num_classes
self.with_pool = with_pool
layer_config = {
18: [2, 2, 2, 2],
34: [3, 4, 6, 3],
50: [3, 4, 6, 3],
101: [3, 4, 23, 3],
152: [3, 8, 36, 3],
}
assert depth in layer_config.keys(), \
"supported depth are {} but input layer is {}".format(
layer_config.keys(), depth)
layers = layer_config[depth]
in_channels = 64
out_channels = [64, 128, 256, 512]
self.conv = ConvBNLayer(
num_channels=3, num_filters=64, filter_size=7, stride=2, act='relu')
self.pool = Pool2D(
pool_size=3, pool_stride=2, pool_padding=1, pool_type='max')
self.layers = []
for idx, num_blocks in enumerate(layers):
blocks = []
shortcut = False
for b in range(num_blocks):
if b == 1:
in_channels = out_channels[idx] * Block.expansion
block = Block(
num_channels=in_channels,
num_filters=out_channels[idx],
stride=2 if b == 0 and idx != 0 else 1,
shortcut=shortcut)
blocks.append(block)
shortcut = True
layer = self.add_sublayer("layer_{}".format(idx),
Sequential(*blocks))
self.layers.append(layer)
if with_pool:
self.global_pool = Pool2D(
pool_size=7, pool_type='avg', global_pooling=True)
if num_classes > 0:
stdv = 1.0 / math.sqrt(out_channels[-1] * Block.expansion * 1.0)
self.fc_input_dim = out_channels[-1] * Block.expansion * 1 * 1
self.fc = Linear(
self.fc_input_dim,
num_classes,
act=classifier_activation,
param_attr=fluid.param_attr.ParamAttr(
initializer=fluid.initializer.Uniform(-stdv, stdv)))
def forward(self, inputs):
x = self.conv(inputs)
x = self.pool(x)
for layer in self.layers:
x = layer(x)
if self.with_pool:
x = self.global_pool(x)
if self.num_classes > -1:
x = fluid.layers.reshape(x, shape=[-1, self.fc_input_dim])
x = self.fc(x)
return x
def _resnet(arch, Block, depth, pretrained, **kwargs):
model = ResNet(Block, depth, **kwargs)
if pretrained:
assert arch in model_urls, "{} model do not have a pretrained model now, you should set pretrained=False".format(
arch)
weight_path = get_weights_path_from_url(model_urls[arch][0],
model_urls[arch][1])
assert weight_path.endswith(
'.pdparams'), "suffix of weight must be .pdparams"
param, _ = fluid.load_dygraph(weight_path)
model.set_dict(param)
return model
def resnet18(pretrained=False, **kwargs):
"""ResNet 18-layer model
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
Examples:
.. code-block:: python
from paddle.vision.models import resnet18
# build model
model = resnet18()
# build model and load imagenet pretrained weight
# model = resnet18(pretrained=True)
"""
return _resnet('resnet18', BasicBlock, 18, pretrained, **kwargs)
def resnet34(pretrained=False, **kwargs):
"""ResNet 34-layer model
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
Examples:
.. code-block:: python
from paddle.vision.models import resnet34
# build model
model = resnet34()
# build model and load imagenet pretrained weight
# model = resnet34(pretrained=True)
"""
return _resnet('resnet34', BasicBlock, 34, pretrained, **kwargs)
def resnet50(pretrained=False, **kwargs):
"""ResNet 50-layer model
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
Examples:
.. code-block:: python
from paddle.vision.models import resnet50
# build model
model = resnet50()
# build model and load imagenet pretrained weight
# model = resnet50(pretrained=True)
"""
return _resnet('resnet50', BottleneckBlock, 50, pretrained, **kwargs)
def resnet101(pretrained=False, **kwargs):
"""ResNet 101-layer model
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
Examples:
.. code-block:: python
from paddle.vision.models import resnet101
# build model
model = resnet101()
# build model and load imagenet pretrained weight
# model = resnet101(pretrained=True)
"""
return _resnet('resnet101', BottleneckBlock, 101, pretrained, **kwargs)
def resnet152(pretrained=False, **kwargs):
"""ResNet 152-layer model
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
Examples:
.. code-block:: python
from paddle.vision.models import resnet152
# build model
model = resnet152()
# build model and load imagenet pretrained weight
# model = resnet152(pretrained=True)
"""
return _resnet('resnet152', BottleneckBlock, 152, pretrained, **kwargs)