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Source code for mmselfsup.models.algorithms.relative_loc
# Copyright (c) OpenMMLab. All rights reserved.
import torch
from ..builder import ALGORITHMS, build_backbone, build_head, build_neck
from .base import BaseModel
[docs]@ALGORITHMS.register_module()
class RelativeLoc(BaseModel):
"""Relative patch location.
Implementation of `Unsupervised Visual Representation Learning
by Context Prediction <https://arxiv.org/abs/1505.05192>`_.
Args:
backbone (dict): Config dict for module of backbone.
neck (dict): Config dict for module of deep features to compact feature
vectors. Defaults to None.
head (dict): Config dict for module of loss functions.
Defaults to None.
"""
def __init__(self, backbone, neck=None, head=None, init_cfg=None):
super(RelativeLoc, self).__init__(init_cfg)
self.backbone = build_backbone(backbone)
assert neck is not None
self.neck = build_neck(neck)
assert head is not None
self.head = build_head(head)
[docs] def extract_feat(self, img):
"""Function to extract features from backbone.
Args:
img (Tensor): Input images of shape (N, C, H, W).
Typically these should be mean centered and std scaled.
Returns:
tuple[Tensor]: backbone outputs.
"""
x = self.backbone(img)
return x
[docs] def forward_train(self, img, patch_label, **kwargs):
"""Forward computation during training.
Args:
img (Tensor): Input images of shape (N, C, H, W).
Typically these should be mean centered and std scaled.
patch_label (Tensor): Labels for the relative patch locations.
kwargs: Any keyword arguments to be used to forward.
Returns:
dict[str, Tensor]: A dictionary of loss components.
"""
img1, img2 = torch.chunk(img, 2, dim=1)
x1 = self.extract_feat(img1) # tuple
x2 = self.extract_feat(img2) # tuple
x = (torch.cat((x1[0], x2[0]), dim=1), )
x = self.neck(x)
outs = self.head(x)
loss_inputs = (outs, patch_label)
losses = self.head.loss(*loss_inputs)
return losses
[docs] def forward_test(self, img, **kwargs):
"""Forward computation during training.
Args:
img (Tensor): Input images of shape (N, C, H, W).
Typically these should be mean centered and std scaled.
Returns:
dict[str, Tensor]: A dictionary of output features.
"""
img1, img2 = torch.chunk(img, 2, dim=1)
x1 = self.extract_feat(img1) # tuple
x2 = self.extract_feat(img2) # tuple
x = (torch.cat((x1[0], x2[0]), dim=1), )
x = self.neck(x)
outs = self.head(x)
keys = [f'head{i}' for i in self.backbone.out_indices]
out_tensors = [out.cpu() for out in outs]
return dict(zip(keys, out_tensors))
[docs] def forward(self, img, patch_label=None, mode='train', **kwargs):
"""Forward function to select mode and modify the input image shape.
Args:
img (Tensor): Input images, the shape depends on mode.
Typically these should be mean centered and std scaled.
"""
if mode != 'extract' and img.dim() == 5: # Nx8x(2C)xHxW
assert patch_label.dim() == 2 # Nx8
img = img.view(
img.size(0) * img.size(1), img.size(2), img.size(3),
img.size(4)) # (8N)x(2C)xHxW
patch_label = torch.flatten(patch_label) # (8N)
if mode == 'train':
return self.forward_train(img, patch_label, **kwargs)
elif mode == 'test':
return self.forward_test(img, **kwargs)
elif mode == 'extract':
return self.extract_feat(img)
else:
raise Exception(f'No such mode: {mode}')