DL-Art-School/codes/models/archs/spinenet_arch.py

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# Taken and modified from https://github.com/lucifer443/SpineNet-Pytorch/blob/master/mmdet/models/backbones/spinenet.py
import torch.nn as nn
import torch.nn.functional as F
from torch.nn.init import kaiming_normal
from torchvision.models.resnet import BasicBlock, Bottleneck
from torch.nn.modules.batchnorm import _BatchNorm
from models.archs.arch_util import ConvBnRelu
def constant_init(module, val, bias=0):
if hasattr(module, 'weight') and module.weight is not None:
nn.init.constant_(module.weight, val)
if hasattr(module, 'bias') and module.bias is not None:
nn.init.constant_(module.bias, bias)
def kaiming_init(module,
a=0,
mode='fan_out',
nonlinearity='relu',
bias=0,
distribution='normal'):
assert distribution in ['uniform', 'normal']
if distribution == 'uniform':
nn.init.kaiming_uniform_(
module.weight, a=a, mode=mode, nonlinearity=nonlinearity)
else:
nn.init.kaiming_normal_(
module.weight, a=a, mode=mode, nonlinearity=nonlinearity)
if hasattr(module, 'bias') and module.bias is not None:
nn.init.constant_(module.bias, bias)
FILTER_SIZE_MAP = {
1: 32,
2: 64,
3: 128,
4: 256,
5: 256,
6: 256,
7: 256,
}
def make_res_layer(block,
inplanes,
planes,
blocks,
stride=1,
dilation=1):
downsample = None
if stride != 1 or inplanes != planes * block.expansion:
downsample = nn.Sequential(
nn.Conv2d(
inplanes,
planes * block.expansion,
kernel_size=1,
stride=stride,
bias=False),
nn.BatchNorm2d(planes * block.expansion),
)
layers = []
layers.append(
block(
inplanes=inplanes,
planes=planes,
stride=stride,
dilation=dilation,
downsample=downsample))
inplanes = planes * block.expansion
for i in range(1, blocks):
layers.append(
block(
inplanes=inplanes,
planes=planes,
stride=1,
dilation=dilation))
return nn.Sequential(*layers)
# The fixed SpineNet architecture discovered by NAS.
# Each element represents a specification of a building block:
# (block_level, block_fn, (input_offset0, input_offset1), is_output).
SPINENET_BLOCK_SPECS = [
(2, Bottleneck, (None, None), False), # init block
(2, Bottleneck, (None, None), False), # init block
(2, Bottleneck, (0, 1), False),
(4, BasicBlock, (0, 1), False),
(3, Bottleneck, (2, 3), False),
(4, Bottleneck, (2, 4), False),
(6, BasicBlock, (3, 5), False),
(4, Bottleneck, (3, 5), False),
(5, BasicBlock, (6, 7), False),
(7, BasicBlock, (6, 8), False),
(5, Bottleneck, (8, 9), False),
(5, Bottleneck, (8, 10), False),
(4, Bottleneck, (5, 10), True),
(3, Bottleneck, (4, 10), True),
(5, Bottleneck, (7, 12), True),
(7, Bottleneck, (5, 14), True),
(6, Bottleneck, (12, 14), True),
]
SCALING_MAP = {
'49S': {
'endpoints_num_filters': 128,
'filter_size_scale': 0.65,
'resample_alpha': 0.5,
'block_repeats': 1,
},
'49': {
'endpoints_num_filters': 256,
'filter_size_scale': 1.0,
'resample_alpha': 0.5,
'block_repeats': 1,
},
'96': {
'endpoints_num_filters': 256,
'filter_size_scale': 1.0,
'resample_alpha': 0.5,
'block_repeats': 2,
},
'143': {
'endpoints_num_filters': 256,
'filter_size_scale': 1.0,
'resample_alpha': 1.0,
'block_repeats': 3,
},
'190': {
'endpoints_num_filters': 512,
'filter_size_scale': 1.3,
'resample_alpha': 1.0,
'block_repeats': 4,
},
}
class BlockSpec(object):
"""A container class that specifies the block configuration for SpineNet."""
def __init__(self, level, block_fn, input_offsets, is_output):
self.level = level
self.block_fn = block_fn
self.input_offsets = input_offsets
self.is_output = is_output
def build_block_specs(block_specs=None):
"""Builds the list of BlockSpec objects for SpineNet."""
if not block_specs:
block_specs = SPINENET_BLOCK_SPECS
return [BlockSpec(*b) for b in block_specs]
class Resample(nn.Module):
def __init__(self, in_channels, out_channels, scale, block_type, alpha=1.0):
super(Resample, self).__init__()
self.scale = scale
new_in_channels = int(in_channels * alpha)
if block_type == Bottleneck:
in_channels *= 4
self.squeeze_conv = ConvBnRelu(in_channels, new_in_channels, kernel_size=1)
if scale < 1:
self.downsample_conv = ConvBnRelu(new_in_channels, new_in_channels, kernel_size=3, stride=2)
self.expand_conv = ConvBnRelu(new_in_channels, out_channels, kernel_size=1, relu=False)
def _resize(self, x):
if self.scale == 1:
return x
elif self.scale > 1:
return F.interpolate(x, scale_factor=self.scale, mode='nearest')
else:
x = self.downsample_conv(x)
if self.scale < 0.5:
new_kernel_size = 3 if self.scale >= 0.25 else 5
x = F.max_pool2d(x, kernel_size=new_kernel_size, stride=int(0.5/self.scale), padding=new_kernel_size//2)
return x
def forward(self, inputs):
feat = self.squeeze_conv(inputs)
feat = self._resize(feat)
feat = self.expand_conv(feat)
return feat
class Merge(nn.Module):
"""Merge two input tensors"""
def __init__(self, block_spec, alpha, filter_size_scale):
super(Merge, self).__init__()
out_channels = int(FILTER_SIZE_MAP[block_spec.level] * filter_size_scale)
if block_spec.block_fn == Bottleneck:
out_channels *= 4
self.block = block_spec.block_fn
self.resample_ops = nn.ModuleList()
for spec_idx in block_spec.input_offsets:
spec = BlockSpec(*SPINENET_BLOCK_SPECS[spec_idx])
in_channels = int(FILTER_SIZE_MAP[spec.level] * filter_size_scale)
scale = 2**(spec.level - block_spec.level)
self.resample_ops.append(
Resample(in_channels, out_channels, scale, spec.block_fn, alpha)
)
def forward(self, inputs):
assert len(inputs) == len(self.resample_ops)
parent0_feat = self.resample_ops[0](inputs[0])
parent1_feat = self.resample_ops[1](inputs[1])
target_feat = parent0_feat + parent1_feat
return target_feat
class SpineNet(nn.Module):
"""Class to build SpineNet backbone"""
def __init__(self,
arch,
in_channels=3,
output_level=[3, 4, 5, 6, 7],
zero_init_residual=True):
super(SpineNet, self).__init__()
self._block_specs = build_block_specs()[2:]
self._endpoints_num_filters = SCALING_MAP[arch]['endpoints_num_filters']
self._resample_alpha = SCALING_MAP[arch]['resample_alpha']
self._block_repeats = SCALING_MAP[arch]['block_repeats']
self._filter_size_scale = SCALING_MAP[arch]['filter_size_scale']
self._init_block_fn = Bottleneck
self._num_init_blocks = 2
self.zero_init_residual = zero_init_residual
assert min(output_level) > 2 and max(output_level) < 8, "Output level out of range"
self.output_level = output_level
self._make_stem_layer(in_channels)
self._make_scale_permuted_network()
self._make_endpoints()
def _make_stem_layer(self, in_channels):
"""Build the stem network."""
# Build the first conv and maxpooling layers.
self.conv1 = ConvBnRelu(
in_channels,
64,
kernel_size=7,
stride=2) # Original paper had stride=2 and a maxpool after.
# Build the initial level 2 blocks.
self.init_block1 = make_res_layer(
self._init_block_fn,
64,
int(FILTER_SIZE_MAP[2] * self._filter_size_scale),
self._block_repeats)
self.init_block2 = make_res_layer(
self._init_block_fn,
int(FILTER_SIZE_MAP[2] * self._filter_size_scale) * 4,
int(FILTER_SIZE_MAP[2] * self._filter_size_scale),
self._block_repeats)
def _make_endpoints(self):
self.endpoint_convs = nn.ModuleDict()
for block_spec in self._block_specs:
if block_spec.is_output:
in_channels = int(FILTER_SIZE_MAP[block_spec.level]*self._filter_size_scale) * 4
self.endpoint_convs[str(block_spec.level)] = ConvBnRelu(in_channels,
self._endpoints_num_filters,
kernel_size=1,
relu=False)
def _make_scale_permuted_network(self):
self.merge_ops = nn.ModuleList()
self.scale_permuted_blocks = nn.ModuleList()
for spec in self._block_specs:
self.merge_ops.append(
Merge(spec, self._resample_alpha, self._filter_size_scale)
)
channels = int(FILTER_SIZE_MAP[spec.level] * self._filter_size_scale)
in_channels = channels * 4 if spec.block_fn == Bottleneck else channels
self.scale_permuted_blocks.append(
make_res_layer(spec.block_fn,
in_channels,
channels,
self._block_repeats)
)
def init_weights(self, pretrained=None):
for m in self.modules():
if isinstance(m, nn.Conv2d):
kaiming_init(m)
elif isinstance(m, (_BatchNorm, nn.GroupNorm)):
constant_init(m, 1)
if self.zero_init_residual:
for m in self.modules():
if isinstance(m, Bottleneck):
constant_init(m.norm3, 0)
elif isinstance(m, BasicBlock):
constant_init(m.norm2, 0)
def forward(self, input):
feat = self.conv1(input)
feat1 = self.init_block1(feat)
feat2 = self.init_block2(feat1)
block_feats = [feat1, feat2]
output_feat = {}
num_outgoing_connections = [0, 0]
for i, spec in enumerate(self._block_specs):
target_feat = self.merge_ops[i]([block_feats[feat_idx] for feat_idx in spec.input_offsets])
# Connect intermediate blocks with outdegree 0 to the output block.
if spec.is_output:
for j, (j_feat, j_connections) in enumerate(
zip(block_feats, num_outgoing_connections)):
if j_connections == 0 and j_feat.shape == target_feat.shape:
target_feat += j_feat
num_outgoing_connections[j] += 1
target_feat = F.relu(target_feat, inplace=True)
target_feat = self.scale_permuted_blocks[i](target_feat)
block_feats.append(target_feat)
num_outgoing_connections.append(0)
for feat_idx in spec.input_offsets:
num_outgoing_connections[feat_idx] += 1
if spec.is_output:
output_feat[spec.level] = target_feat
return [self.endpoint_convs[str(level)](output_feat[level]) for level in self.output_level]