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# Modified from https://github.com/mseitzer/pytorch-fid/blob/master/pytorch_fid/inception.py # noqa: E501
# For FID metric
import os
import torch
import torch.nn as nn
import torch.nn.functional as F
from torch.utils.model_zoo import load_url
from torchvision import models
# Inception weights ported to Pytorch from
# http://download.tensorflow.org/models/image/imagenet/inception-2015-12-05.tgz
FID_WEIGHTS_URL = 'https://github.com/mseitzer/pytorch-fid/releases/download/fid_weights/pt_inception-2015-12-05-6726825d.pth' # noqa: E501
LOCAL_FID_WEIGHTS = 'experiments/pretrained_models/pt_inception-2015-12-05-6726825d.pth' # noqa: E501
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.
Args:
output_blocks (list[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. Default: True.
normalize_input (bool): If true, scales the input from range (0, 1)
to the range the pretrained Inception network expects,
namely (-1, 1). Default: True.
requires_grad (bool): If true, parameters of the model require
gradients. Possibly useful for finetuning the network.
Default: False.
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. Default: True.
"""
super(InceptionV3, self).__init__()
self.resize_input = resize_input
self.normalize_input = normalize_input
self.output_blocks = sorted(output_blocks)
self.last_needed_block = max(output_blocks)
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:
try:
inception = models.inception_v3(pretrained=True, init_weights=False)
except TypeError:
# pytorch < 1.5 does not have init_weights for inception_v3
inception = models.inception_v3(pretrained=True)
# 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:
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
def forward(self, x):
"""Get Inception feature maps.
Args:
x (Tensor): Input tensor of shape (b, 3, h, w).
Values are expected to be in range (-1, 1). You can also input
(0, 1) with setting normalize_input = True.
Returns:
list[Tensor]: Corresponding to the selected output block, sorted
ascending by index.
"""
output = []
if self.resize_input:
x = F.interpolate(x, size=(299, 299), mode='bilinear', align_corners=False)
if self.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 idx in self.output_blocks:
output.append(x)
if idx == self.last_needed_block:
break
return output
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.
"""
try:
inception = models.inception_v3(num_classes=1008, aux_logits=False, pretrained=False, init_weights=False)
except TypeError:
# pytorch < 1.5 does not have init_weights for inception_v3
inception = models.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)
if os.path.exists(LOCAL_FID_WEIGHTS):
state_dict = torch.load(LOCAL_FID_WEIGHTS, map_location=lambda storage, loc: storage)
else:
state_dict = load_url(FID_WEIGHTS_URL, progress=True)
inception.load_state_dict(state_dict)
return inception
class FIDInceptionA(models.inception.InceptionA):
"""InceptionA block patched for FID computation"""
def __init__(self, in_channels, pool_features):
super(FIDInceptionA, self).__init__(in_channels, pool_features)
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)
class FIDInceptionC(models.inception.InceptionC):
"""InceptionC block patched for FID computation"""
def __init__(self, in_channels, channels_7x7):
super(FIDInceptionC, self).__init__(in_channels, channels_7x7)
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)
class FIDInceptionE_1(models.inception.InceptionE):
"""First InceptionE block patched for FID computation"""
def __init__(self, in_channels):
super(FIDInceptionE_1, self).__init__(in_channels)
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)
class FIDInceptionE_2(models.inception.InceptionE):
"""Second InceptionE block patched for FID computation"""
def __init__(self, in_channels):
super(FIDInceptionE_2, self).__init__(in_channels)
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)
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