"""
File from: https://github.com/mseitzer/pytorch-fid
"""
import torch
import torch.nn as nn
import torch.nn.functional as F
import torchvision
from .arch_util import load_pretrained_network
from .arch_util import get_url_from_name
[docs]
FID_WEIGHTS_URL = get_url_from_name('pt_inception-2015-12-05-6726825d.pth')
[docs]
class InceptionV3(nn.Module):
"""Pretrained InceptionV3 network returning feature maps"""
# Index of default block of inception to return,
# corresponds to output of final average pooling
DEFAULT_BLOCK_INDEX = 3
# Maps feature dimensionality to their output blocks indices
BLOCK_INDEX_BY_DIM = {
64: 0, # First max pooling features
192: 1, # Second max pooling features
768: 2, # Pre-aux classifier features
2048: 3, # Final average pooling features
}
def __init__(
self,
output_blocks=(DEFAULT_BLOCK_INDEX,),
resize_input=True,
normalize_input=True,
requires_grad=False,
use_fid_inception=True,
):
"""Build pretrained InceptionV3
Parameters
----------
- output_blocks : list of int
Indices of blocks to return features of. Possible values are:
- 0: corresponds to output of first max pooling
- 1: corresponds to output of second max pooling
- 2: corresponds to output which is fed to aux classifier
- 3: corresponds to output of final average pooling
- resize_input : bool
If true, bilinearly resizes input to width and height 299 before
feeding input to model. As the network without fully connected
layers is fully convolutional, it should be able to handle inputs
of arbitrary size, so resizing might not be strictly needed
- normalize_input : bool
If true, scales the input from range (0, 1) to the range the
pretrained Inception network expects, namely (-1, 1)
- requires_grad : bool
If true, parameters of the model require gradients. Possibly useful
for finetuning the network
- use_fid_inception : bool
If true, uses the pretrained Inception model used in Tensorflow's
FID implementation. If false, uses the pretrained Inception model
available in torchvision. The FID Inception model has different
weights and a slightly different structure from torchvision's
Inception model. If you want to compute FID scores, you are
strongly advised to set this parameter to true to get comparable
results.
"""
super(InceptionV3, self).__init__()
self.resize_input = resize_input
self.normalize_input = normalize_input
if isinstance(output_blocks, (list, tuple)):
self.output_blocks = sorted(output_blocks)
self.last_needed_block = max(output_blocks)
elif isinstance(output_blocks, str):
if 'logits' in output_blocks:
self.output_blocks = output_blocks
self.last_needed_block = 3
elif 'mixed_6a' in output_blocks:
self.output_blocks = output_blocks
self.last_needed_block = 2
assert self.last_needed_block <= 3, 'Last possible output block index is 3'
self.blocks = nn.ModuleList()
if use_fid_inception:
inception = fid_inception_v3()
else:
inception = _inception_v3(pretrained=True)
self.fc = inception.fc
# Block 0: input to maxpool1
block0 = [
inception.Conv2d_1a_3x3,
inception.Conv2d_2a_3x3,
inception.Conv2d_2b_3x3,
nn.MaxPool2d(kernel_size=3, stride=2),
]
self.blocks.append(nn.Sequential(*block0))
# Block 1: maxpool1 to maxpool2
if self.last_needed_block >= 1:
block1 = [
inception.Conv2d_3b_1x1,
inception.Conv2d_4a_3x3,
nn.MaxPool2d(kernel_size=3, stride=2),
]
self.blocks.append(nn.Sequential(*block1))
# Block 2: maxpool2 to aux classifier
if self.last_needed_block >= 2:
if self.output_blocks == 'mixed_6a':
block2 = [
inception.Mixed_5b,
inception.Mixed_5c,
inception.Mixed_5d,
inception.Mixed_6a,
]
else:
block2 = [
inception.Mixed_5b,
inception.Mixed_5c,
inception.Mixed_5d,
inception.Mixed_6a,
inception.Mixed_6b,
inception.Mixed_6c,
inception.Mixed_6d,
inception.Mixed_6e,
]
self.blocks.append(nn.Sequential(*block2))
# Block 3: aux classifier to final avgpool
if self.last_needed_block >= 3:
block3 = [
inception.Mixed_7a,
inception.Mixed_7b,
inception.Mixed_7c,
nn.AdaptiveAvgPool2d(output_size=(1, 1)),
]
self.blocks.append(nn.Sequential(*block3))
for param in self.parameters():
param.requires_grad = requires_grad
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def forward(self, inp, resize_input=False, normalize_input=False):
"""Get Inception feature maps
Parameters
----------
inp : torch.autograd.Variable
Input tensor of shape Bx3xHxW. Values are expected to be in
range (0, 1)
Returns
-------
List of torch.autograd.Variable, corresponding to the selected output
block, sorted ascending by index
"""
outp = []
x = inp
if resize_input:
x = F.interpolate(x, size=(299, 299), mode='bilinear', align_corners=False)
if normalize_input:
x = 2 * x - 1 # Scale from range (0, 1) to range (-1, 1)
for idx, block in enumerate(self.blocks):
x = block(x)
if not isinstance(self.output_blocks, str) and idx in self.output_blocks:
outp.append(x)
if idx == self.last_needed_block:
break
if self.output_blocks == 'mixed_6a':
# If the output block is 'mixed_6a', we return the features of the
# last block before the aux classifier, which is Mixed_6a.
outp.append(x)
if self.output_blocks == 'logits_unbiased':
outp.append(x.flatten(1).mm(self.fc.weight.T))
elif self.output_blocks == 'logits':
outp.append(self.fc(x))
return outp
def _inception_v3(*args, **kwargs):
"""Wraps `torchvision.models.inception_v3`
Skips default weight initialization if supported by torchvision version.
See https://github.com/mseitzer/pytorch-fid/issues/28.
"""
try:
version = tuple(map(int, torchvision.__version__.split('.')[:2]))
except ValueError:
# Just a caution against weird version strings
version = (0,)
if version >= (0, 6):
kwargs['init_weights'] = False
return torchvision.models.inception_v3(*args, **kwargs)
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def fid_inception_v3():
"""Build pretrained Inception model for FID computation
The Inception model for FID computation uses a different set of weights
and has a slightly different structure than torchvision's Inception.
This method first constructs torchvision's Inception and then patches the
necessary parts that are different in the FID Inception model.
"""
inception = _inception_v3(num_classes=1008, aux_logits=False, pretrained=False)
inception.Mixed_5b = FIDInceptionA(192, pool_features=32)
inception.Mixed_5c = FIDInceptionA(256, pool_features=64)
inception.Mixed_5d = FIDInceptionA(288, pool_features=64)
inception.Mixed_6b = FIDInceptionC(768, channels_7x7=128)
inception.Mixed_6c = FIDInceptionC(768, channels_7x7=160)
inception.Mixed_6d = FIDInceptionC(768, channels_7x7=160)
inception.Mixed_6e = FIDInceptionC(768, channels_7x7=192)
inception.Mixed_7b = FIDInceptionE_1(1280)
inception.Mixed_7c = FIDInceptionE_2(2048)
load_pretrained_network(inception, FID_WEIGHTS_URL)
return inception
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class FIDInceptionA(torchvision.models.inception.InceptionA):
"""InceptionA block patched for FID computation"""
def __init__(self, in_channels, pool_features):
super(FIDInceptionA, self).__init__(in_channels, pool_features)
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def forward(self, x):
branch1x1 = self.branch1x1(x)
branch5x5 = self.branch5x5_1(x)
branch5x5 = self.branch5x5_2(branch5x5)
branch3x3dbl = self.branch3x3dbl_1(x)
branch3x3dbl = self.branch3x3dbl_2(branch3x3dbl)
branch3x3dbl = self.branch3x3dbl_3(branch3x3dbl)
# Patch: Tensorflow's average pool does not use the padded zero's in
# its average calculation
branch_pool = F.avg_pool2d(
x, kernel_size=3, stride=1, padding=1, count_include_pad=False
)
branch_pool = self.branch_pool(branch_pool)
outputs = [branch1x1, branch5x5, branch3x3dbl, branch_pool]
return torch.cat(outputs, 1)
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class FIDInceptionC(torchvision.models.inception.InceptionC):
"""InceptionC block patched for FID computation"""
def __init__(self, in_channels, channels_7x7):
super(FIDInceptionC, self).__init__(in_channels, channels_7x7)
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def forward(self, x):
branch1x1 = self.branch1x1(x)
branch7x7 = self.branch7x7_1(x)
branch7x7 = self.branch7x7_2(branch7x7)
branch7x7 = self.branch7x7_3(branch7x7)
branch7x7dbl = self.branch7x7dbl_1(x)
branch7x7dbl = self.branch7x7dbl_2(branch7x7dbl)
branch7x7dbl = self.branch7x7dbl_3(branch7x7dbl)
branch7x7dbl = self.branch7x7dbl_4(branch7x7dbl)
branch7x7dbl = self.branch7x7dbl_5(branch7x7dbl)
# Patch: Tensorflow's average pool does not use the padded zero's in
# its average calculation
branch_pool = F.avg_pool2d(
x, kernel_size=3, stride=1, padding=1, count_include_pad=False
)
branch_pool = self.branch_pool(branch_pool)
outputs = [branch1x1, branch7x7, branch7x7dbl, branch_pool]
return torch.cat(outputs, 1)
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class FIDInceptionE_1(torchvision.models.inception.InceptionE):
"""First InceptionE block patched for FID computation"""
def __init__(self, in_channels):
super(FIDInceptionE_1, self).__init__(in_channels)
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def forward(self, x):
branch1x1 = self.branch1x1(x)
branch3x3 = self.branch3x3_1(x)
branch3x3 = [
self.branch3x3_2a(branch3x3),
self.branch3x3_2b(branch3x3),
]
branch3x3 = torch.cat(branch3x3, 1)
branch3x3dbl = self.branch3x3dbl_1(x)
branch3x3dbl = self.branch3x3dbl_2(branch3x3dbl)
branch3x3dbl = [
self.branch3x3dbl_3a(branch3x3dbl),
self.branch3x3dbl_3b(branch3x3dbl),
]
branch3x3dbl = torch.cat(branch3x3dbl, 1)
# Patch: Tensorflow's average pool does not use the padded zero's in
# its average calculation
branch_pool = F.avg_pool2d(
x, kernel_size=3, stride=1, padding=1, count_include_pad=False
)
branch_pool = self.branch_pool(branch_pool)
outputs = [branch1x1, branch3x3, branch3x3dbl, branch_pool]
return torch.cat(outputs, 1)
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class FIDInceptionE_2(torchvision.models.inception.InceptionE):
"""Second InceptionE block patched for FID computation"""
def __init__(self, in_channels):
super(FIDInceptionE_2, self).__init__(in_channels)
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def forward(self, x):
branch1x1 = self.branch1x1(x)
branch3x3 = self.branch3x3_1(x)
branch3x3 = [
self.branch3x3_2a(branch3x3),
self.branch3x3_2b(branch3x3),
]
branch3x3 = torch.cat(branch3x3, 1)
branch3x3dbl = self.branch3x3dbl_1(x)
branch3x3dbl = self.branch3x3dbl_2(branch3x3dbl)
branch3x3dbl = [
self.branch3x3dbl_3a(branch3x3dbl),
self.branch3x3dbl_3b(branch3x3dbl),
]
branch3x3dbl = torch.cat(branch3x3dbl, 1)
# Patch: The FID Inception model uses max pooling instead of average
# pooling. This is likely an error in this specific Inception
# implementation, as other Inception models use average pooling here
# (which matches the description in the paper).
branch_pool = F.max_pool2d(x, kernel_size=3, stride=1, padding=1)
branch_pool = self.branch_pool(branch_pool)
outputs = [branch1x1, branch3x3, branch3x3dbl, branch_pool]
return torch.cat(outputs, 1)