[Enhance] Enhance feature extraction function. (open-mmlab#593)

* Fix MobileNet V3 configs

* Refactor to support more powerful feature extraction.

* Add unit tests

* Fix unit test

* Imporve according to comments

* Update checkpoints path

* Fix unit tests

* Add docstring of `simple_test`

* Add docstring of `extract_feat`

* Update model zoo

configs/_base_/models/mobilenet_v3_large_imagenet.py

@@ -11,4 +11,6 @@
         dropout_rate=0.2,
         act_cfg=dict(type='HSwish'),
         loss=dict(type='CrossEntropyLoss', loss_weight=1.0),
+        init_cfg=dict(
+            type='Normal', layer='Linear', mean=0., std=0.01, bias=0.),
         topk=(1, 5)))

configs/_base_/models/mobilenet_v3_small_imagenet.py

@@ -11,4 +11,6 @@
         dropout_rate=0.2,
         act_cfg=dict(type='HSwish'),
         loss=dict(type='CrossEntropyLoss', loss_weight=1.0),
+        init_cfg=dict(
+            type='Normal', layer='Linear', mean=0., std=0.01, bias=0.),
         topk=(1, 5)))

configs/deit/README.md

@@ -34,11 +34,11 @@ The pre-trained models are converted from the [official repo](https://github.com
 |         Model         | Params(M) | Flops(G) | Top-1 (%) | Top-5 (%) | Config | Download |
 |:---------------------:|:---------:|:--------:|:---------:|:---------:|:------:|:--------:|
 | DeiT-tiny\* | 5.72 | 1.08 | 72.13 | 91.13 | [config](configs/deit/deit-tiny_pt-4xb256_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-tiny_3rdparty_pt-4xb256_in1k_20211124-e930093b.pth) |
-| DeiT-tiny distilled\* | 5.72 | 1.08 | 74.51 | 91.90 | [config](configs/deit/deit-tiny-distilled_pt-4xb256_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-tiny-distilled_3rdparty_pt-4xb256_in1k_20211124-e71bdd9a.pth) |
+| DeiT-tiny distilled\* | 5.72 | 1.08 | 74.51 | 91.90 | [config](configs/deit/deit-tiny-distilled_pt-4xb256_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-tiny-distilled_3rdparty_pt-4xb256_in1k_20211216-c429839a.pth) |
 | DeiT-small\* | 22.05 | 4.24 | 79.83 | 94.95 | [config](configs/deit/deit-small_pt-4xb256_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-small_3rdparty_pt-4xb256_in1k_20211124-ffe94edd.pth) |
-| DeiT-small distilled\* | 22.05 | 4.24 | 81.17 | 95.40 | [config](configs/deit/deit-small-distilled_pt-4xb256_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-small-distilled_3rdparty_pt-4xb256_in1k_20211124-15e341b0.pth) |
+| DeiT-small distilled\* | 22.05 | 4.24 | 81.17 | 95.40 | [config](configs/deit/deit-small-distilled_pt-4xb256_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-small-distilled_3rdparty_pt-4xb256_in1k_20211216-4de1d725.pth) |
 | DeiT-base\* | 86.57 | 16.86 | 81.79 | 95.59 | [config](configs/deit/deit-base_pt-16xb64_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-base_3rdparty_pt-16xb64_in1k_20211124-6f40c188.pth) |
-| DeiT-base distilled\* | 86.57 | 16.86 | 83.33 | 96.49 | [config](configs/deit/deit-base-distilled_pt-16xb64_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-base-distilled_3rdparty_pt-16xb64_in1k_20211124-766d123d.pth) |
+| DeiT-base distilled\* | 86.57 | 16.86 | 83.33 | 96.49 | [config](configs/deit/deit-base-distilled_pt-16xb64_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-base-distilled_3rdparty_pt-16xb64_in1k_20211216-42891296.pth) |
 
 *Models with \* are converted from other repos.*
 
@@ -51,7 +51,7 @@ The fine-tuned models are converted from the [official repo](https://github.com/
 |         Model         | Params(M) | Flops(G) | Top-1 (%) | Top-5 (%) | Config | Download |
 |:---------------------:|:---------:|:--------:|:---------:|:---------:|:------:|:--------:|
 | DeiT-base 384px\* | 86.86 | 49.37 | 83.04 | 96.31 | [config](configs/deit/deit-base_ft-16xb32_in1k-384px.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-base_3rdparty_ft-16xb32_in1k-384px_20211124-822d02f2.pth) |
-| DeiT-base distilled 384px\* | 86.86 | 49.37 | 85.55 | 97.35 | [config](configs/deit/deit-base-distilled_ft-16xb32_in1k-384px.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-base-distilled_3rdparty_ft-16xb32_in1k-384px_20211124-91e88933.pth) |
+| DeiT-base distilled 384px\* | 86.86 | 49.37 | 85.55 | 97.35 | [config](configs/deit/deit-base-distilled_ft-16xb32_in1k-384px.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-base-distilled_3rdparty_ft-16xb32_in1k-384px_20211216-e48d6000.pth) |
 
 *Models with \* are converted from other repos.*
 

configs/deit/metafile.yml

@@ -40,7 +40,7 @@ Models:
           Top 1 Accuracy: 74.51
           Top 5 Accuracy: 91.90
         Task: Image Classification
-    Weights: https://download.openmmlab.com/mmclassification/v0/deit/deit-tiny-distilled_3rdparty_pt-4xb256_in1k_20211124-e71bdd9a.pth
+    Weights: https://download.openmmlab.com/mmclassification/v0/deit/deit-tiny-distilled_3rdparty_pt-4xb256_in1k_20211216-c429839a.pth
     Converted From:
       Weights: https://dl.fbaipublicfiles.com/deit/deit_tiny_distilled_patch16_224-b40b3cf7.pth
       Code: https://github.com/facebookresearch/deit/blob/f5123946205daf72a88783dae94cabff98c49c55/models.py#L108
@@ -72,7 +72,7 @@ Models:
           Top 1 Accuracy: 81.17
           Top 5 Accuracy: 95.40
         Task: Image Classification
-    Weights: https://download.openmmlab.com/mmclassification/v0/deit/deit-small-distilled_3rdparty_pt-4xb256_in1k_20211124-15e341b0.pth
+    Weights: https://download.openmmlab.com/mmclassification/v0/deit/deit-small-distilled_3rdparty_pt-4xb256_in1k_20211216-4de1d725.pth
     Converted From:
       Weights: https://dl.fbaipublicfiles.com/deit/deit_small_distilled_patch16_224-649709d9.pth
       Code: https://github.com/facebookresearch/deit/blob/f5123946205daf72a88783dae94cabff98c49c55/models.py#L123
@@ -104,7 +104,7 @@ Models:
           Top 1 Accuracy: 83.33
           Top 5 Accuracy: 96.49
         Task: Image Classification
-    Weights: https://download.openmmlab.com/mmclassification/v0/deit/deit-base-distilled_3rdparty_pt-16xb64_in1k_20211124-766d123d.pth
+    Weights: https://download.openmmlab.com/mmclassification/v0/deit/deit-base-distilled_3rdparty_pt-16xb64_in1k_20211216-42891296.pth
     Converted From:
       Weights: https://dl.fbaipublicfiles.com/deit/deit_base_distilled_patch16_224-df68dfff.pth
       Code: https://github.com/facebookresearch/deit/blob/f5123946205daf72a88783dae94cabff98c49c55/models.py#L138
@@ -136,7 +136,7 @@ Models:
           Top 1 Accuracy: 85.55
           Top 5 Accuracy: 97.35
         Task: Image Classification
-    Weights: https://download.openmmlab.com/mmclassification/v0/deit/deit-base-distilled_3rdparty_ft-16xb32_in1k-384px_20211124-91e88933.pth
+    Weights: https://download.openmmlab.com/mmclassification/v0/deit/deit-base-distilled_3rdparty_ft-16xb32_in1k-384px_20211216-e48d6000.pth
     Converted From:
       Weights: https://dl.fbaipublicfiles.com/deit/deit_base_distilled_patch16_384-d0272ac0.pth
       Code: https://github.com/facebookresearch/deit/blob/f5123946205daf72a88783dae94cabff98c49c55/models.py#L168

configs/mobilenet_v3/mobilenet-v3-small_8xb32_in1k.py

@@ -17,7 +17,7 @@
 # - modify: RandomErasing use RE-M instead of RE-0
 
 _base_ = [
-    '../_base_/models/mobilenet-v3-small_8xb32_in1k.py',
+    '../_base_/models/mobilenet_v3_small_imagenet.py',
     '../_base_/datasets/imagenet_bs32_pil_resize.py',
     '../_base_/default_runtime.py'
 ]

docs/en/model_zoo.md

@@ -63,16 +63,18 @@ The ResNet family models below are trained by standard data augmentations, i.e.,
 | T2T-ViT_t-24\* |   64.00   | 12.69    | 82.55     | 96.06     | [config](https://github.com/open-mmlab/mmclassification/blob/master/configs/t2t_vit/t2t-vit-t-24_8xb64_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/t2t-vit/t2t-vit-t-24_3rdparty_8xb64_in1k_20210928-fe95a61b.pth)  | [log]()|
 |  Mixer-B/16\*  |  59.88   |  12.61    | 76.68     | 92.25     | [config](https://github.com/open-mmlab/mmclassification/blob/master/configs/mlp_mixer/mlp-mixer-base-p16_64xb64_in1k.py)  | [model](https://download.openmmlab.com/mmclassification/v0/mlp-mixer/mixer-base-p16_3rdparty_64xb64_in1k_20211124-1377e3e0.pth)  | [log]()|
 |  Mixer-L/16\*  |  208.2   |  44.57    | 72.34     | 88.02     | [config](https://github.com/open-mmlab/mmclassification/blob/master/configs/mlp_mixer/mlp-mixer-large-p16_64xb64_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/mlp-mixer/mixer-large-p16_3rdparty_64xb64_in1k_20211124-5a2519d2.pth)  | [log]()|
-| DeiT-tiny\* | 5.72 | 1.08 | 72.13 | 91.13 | [config](configs/deit/deit-tiny_pt-4xb256_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-tiny_3rdparty_pt-4xb256_in1k_20211124-e930093b.pth)  | [log]()|
-| DeiT-tiny distilled\* | 5.72 | 1.08 | 74.51 | 91.90 | [config](configs/deit/deit-tiny-distilled_pt-4xb256_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-tiny-distilled_3rdparty_pt-4xb256_in1k_20211124-e71bdd9a.pth)  | [log]()|
-| DeiT-small\* | 22.05 | 4.24 | 79.83 | 94.95 | [config](configs/deit/deit-small_pt-4xb256_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-small_3rdparty_pt-4xb256_in1k_20211124-ffe94edd.pth)  | [log]()|
-| DeiT-small distilled\* | 22.05 | 4.24 | 81.17 | 95.40 | [config](configs/deit/deit-small-distilled_pt-4xb256_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-small-distilled_3rdparty_pt-4xb256_in1k_20211124-15e341b0.pth)  | [log]()|
-| DeiT-base\* | 86.57 | 16.86 | 81.79 | 95.59 | [config](configs/deit/deit-base_pt-16xb64_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-base_3rdparty_pt-16xb64_in1k_20211124-6f40c188.pth)  | [log]()|
-| DeiT-base distilled\* | 86.57 | 16.86 | 83.33 | 96.49 | [config](configs/deit/deit-base-distilled_pt-16xb64_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-base-distilled_3rdparty_pt-16xb64_in1k_20211124-766d123d.pth)  | [log]()|
-| Conformer-tiny-p16\*  |  23.52    | 4.90 | 81.31 | 95.60 | [config](configs/conformer/conformer-tiny-p16_8xb128_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/conformer/conformer-tiny-p16_3rdparty_8xb128_in1k_20211206-f6860372.pth)  | [log]()|
-| Conformer-small-p32   |  38.85    | 7.09 | 81.96 | 96.02 | [config](configs/conformer/conformer-small-p32_8xb128_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/conformer/conformer-small-p32_8xb128_in1k_20211206-947a0816.pth)  | [log]()|
-| Conformer-small-p16\* |  37.67    | 10.31 | 83.32 | 96.46 | [config](configs/conformer/conformer-small-p16_8xb128_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/conformer/conformer-small-p16_3rdparty_8xb128_in1k_20211206-3065dcf5.pth)  | [log]()|
-| Conformer-base-p16\*  |  83.29    | 22.89 | 83.82 | 96.59 | [config](configs/conformer/conformer-base-p16_8xb128_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/conformer/conformer-base-p16_3rdparty_8xb128_in1k_20211206-bfdf8637.pth)  | [log]()|
+| DeiT-tiny\* | 5.72 | 1.08 | 72.13 | 91.13 | [config](https://github.com/open-mmlab/mmclassification/blob/master/configs/deit/deit-tiny_pt-4xb256_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-tiny_3rdparty_pt-4xb256_in1k_20211124-e930093b.pth)  | [log]()|
+| DeiT-tiny distilled\* | 5.72 | 1.08 | 74.51 | 91.90 | [config](https://github.com/open-mmlab/mmclassification/blob/master/configs/deit/deit-tiny-distilled_pt-4xb256_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-tiny-distilled_3rdparty_pt-4xb256_in1k_20211216-c429839a.pth)  | [log]()|
+| DeiT-small\* | 22.05 | 4.24 | 79.83 | 94.95 | [config](https://github.com/open-mmlab/mmclassification/blob/master/configs/deit/deit-small_pt-4xb256_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-small_3rdparty_pt-4xb256_in1k_20211124-ffe94edd.pth)  | [log]()|
+| DeiT-small distilled\* | 22.05 | 4.24 | 81.17 | 95.40 | [config](https://github.com/open-mmlab/mmclassification/blob/master/configs/deit/deit-small-distilled_pt-4xb256_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-small-distilled_3rdparty_pt-4xb256_in1k_20211216-4de1d725.pth)  | [log]()|
+| DeiT-base\* | 86.57 | 16.86 | 81.79 | 95.59 | [config](https://github.com/open-mmlab/mmclassification/blob/master/configs/deit/deit-base_pt-16xb64_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-base_3rdparty_pt-16xb64_in1k_20211124-6f40c188.pth)  | [log]()|
+| DeiT-base distilled\* | 86.57 | 16.86 | 83.33 | 96.49 | [config](https://github.com/open-mmlab/mmclassification/blob/master/configs/deit/deit-base-distilled_pt-16xb64_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-base-distilled_3rdparty_pt-16xb64_in1k_20211216-42891296.pth)  | [log]()|
+| DeiT-base 384px\* | 86.86 | 49.37 | 83.04 | 96.31 | [config](https://github.com/open-mmlab/mmclassification/blob/master/configs/deit/deit-base_ft-16xb32_in1k-384px.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-base_3rdparty_ft-16xb32_in1k-384px_20211124-822d02f2.pth)  | [log]()|
+| DeiT-base distilled 384px\* | 86.86 | 49.37 | 85.55 | 97.35 | [config](https://github.com/open-mmlab/mmclassification/blob/master/configs/deit/deit-base-distilled_ft-16xb32_in1k-384px.py) | [model](https://download.openmmlab.com/mmclassification/v0/deit/deit-base-distilled_3rdparty_ft-16xb32_in1k-384px_20211216-e48d6000.pth)  | [log]()|
+| Conformer-tiny-p16\*  |  23.52    | 4.90 | 81.31 | 95.60 | [config](https://github.com/open-mmlab/mmclassification/blob/master/configs/conformer/conformer-tiny-p16_8xb128_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/conformer/conformer-tiny-p16_3rdparty_8xb128_in1k_20211206-f6860372.pth)  | [log]()|
+| Conformer-small-p32   |  38.85    | 7.09 | 81.96 | 96.02 | [config](https://github.com/open-mmlab/mmclassification/blob/master/configs/conformer/conformer-small-p32_8xb128_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/conformer/conformer-small-p32_8xb128_in1k_20211206-947a0816.pth)  | [log]()|
+| Conformer-small-p16\* |  37.67    | 10.31 | 83.32 | 96.46 | [config](https://github.com/open-mmlab/mmclassification/blob/master/configs/conformer/conformer-small-p16_8xb128_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/conformer/conformer-small-p16_3rdparty_8xb128_in1k_20211206-3065dcf5.pth)  | [log]()|
+| Conformer-base-p16\*  |  83.29    | 22.89 | 83.82 | 96.59 | [config](https://github.com/open-mmlab/mmclassification/blob/master/configs/conformer/conformer-base-p16_8xb128_in1k.py) | [model](https://download.openmmlab.com/mmclassification/v0/conformer/conformer-base-p16_3rdparty_8xb128_in1k_20211206-bfdf8637.pth)  | [log]()|
 
 Models with * are converted from other repos, others are trained by ourselves.
 

mmcls/models/classifiers/base.py

@@ -2,6 +2,7 @@
 import warnings
 from abc import ABCMeta, abstractmethod
 from collections import OrderedDict
+from typing import Sequence
 
 import mmcv
 import torch
@@ -35,13 +36,14 @@ def with_head(self):
         return hasattr(self, 'head') and self.head is not None
 
     @abstractmethod
-    def extract_feat(self, imgs):
+    def extract_feat(self, imgs, stage=None):
         pass
 
-    def extract_feats(self, imgs):
-        assert isinstance(imgs, list)
+    def extract_feats(self, imgs, stage=None):
+        assert isinstance(imgs, Sequence)
+        kwargs = {} if stage is None else {'stage': stage}
         for img in imgs:
-            yield self.extract_feat(img)
+            yield self.extract_feat(img, **kwargs)
 
     @abstractmethod
     def forward_train(self, imgs, **kwargs):

mmcls/models/classifiers/image.py

@@ -3,6 +3,7 @@
 import warnings
 
 from ..builder import CLASSIFIERS, build_backbone, build_head, build_neck
+from ..heads import MultiLabelClsHead
 from ..utils.augment import Augments
 from .base import BaseClassifier
 
@@ -70,8 +71,74 @@ def __init__(self,
                     cfg['prob'] = cutmix_prob
                     self.augments = Augments(cfg)
 
-    def extract_feat(self, img):
-        """Directly extract features from the backbone + neck."""
+    def extract_feat(self, img, stage='neck'):
+        """Directly extract features from the specified stage.
+
+        Args:
+            img (Tensor): The input images. The shape of it should be
+                ``(num_samples, num_channels, *img_shape)``.
+            stage (str): Which stage to output the feature. Choose from
+                "backbone", "neck" and "pre_logits". Defaults to "neck".
+
+        Returns:
+            tuple | Tensor: The output of specified stage.
+                The output depends on detailed implementation. In general, the
+                output of backbone and neck is a tuple and the output of
+                pre_logits is a tensor.
+
+        Examples:
+            1. Backbone output
+
+            >>> import torch
+            >>> from mmcv import Config
+            >>> from mmcls.models import build_classifier
+            >>>
+            >>> cfg = Config.fromfile('configs/resnet/resnet18_8xb32_in1k.py').model
+            >>> cfg.backbone.out_indices = (0, 1, 2, 3)  # Output multi-scale feature maps
+            >>> model = build_classifier(cfg)
+            >>> outs = model.extract_feat(torch.rand(1, 3, 224, 224), stage='backbone')
+            >>> for out in outs:
+            ...     print(out.shape)
+            torch.Size([1, 64, 56, 56])
+            torch.Size([1, 128, 28, 28])
+            torch.Size([1, 256, 14, 14])
+            torch.Size([1, 512, 7, 7])
+
+            2. Neck output
+
+            >>> import torch
+            >>> from mmcv import Config
+            >>> from mmcls.models import build_classifier
+            >>>
+            >>> cfg = Config.fromfile('configs/resnet/resnet18_8xb32_in1k.py').model
+            >>> cfg.backbone.out_indices = (0, 1, 2, 3)  # Output multi-scale feature maps
+            >>> model = build_classifier(cfg)
+            >>>
+            >>> outs = model.extract_feat(torch.rand(1, 3, 224, 224), stage='neck')
+            >>> for out in outs:
+            ...     print(out.shape)
+            torch.Size([1, 64])
+            torch.Size([1, 128])
+            torch.Size([1, 256])
+            torch.Size([1, 512])
+
+            3. Pre-logits output (without the final linear classifier head)
+
+            >>> import torch
+            >>> from mmcv import Config
+            >>> from mmcls.models import build_classifier
+            >>>
+            >>> cfg = Config.fromfile('configs/vision_transformer/vit-base-p16_pt-64xb64_in1k-224.py').model
+            >>> model = build_classifier(cfg)
+            >>>
+            >>> out = model.extract_feat(torch.rand(1, 3, 224, 224), stage='pre_logits')
+            >>> print(out.shape)  # The hidden dims in head is 3072
+            torch.Size([1, 3072])
+        """  # noqa: E501
+        assert stage in ['backbone', 'neck', 'pre_logits'], \
+            (f'Invalid output stage "{stage}", please choose from "backbone", '
+             '"neck" and "pre_logits"')
+
         x = self.backbone(img)
         if self.return_tuple:
             if not isinstance(x, tuple):
@@ -83,8 +150,16 @@ def extract_feat(self, img):
         else:
             if isinstance(x, tuple):
                 x = x[-1]
+        if stage == 'backbone':
+            return x
+
         if self.with_neck:
             x = self.neck(x)
+        if stage == 'neck':
+            return x
+
+        if self.with_head and hasattr(self.head, 'pre_logits'):
+            x = self.head.pre_logits(x)
         return x
 
     def forward_train(self, img, gt_label, **kwargs):
@@ -122,12 +197,16 @@ def forward_train(self, img, gt_label, **kwargs):
 
         return losses
 
-    def simple_test(self, img, img_metas):
+    def simple_test(self, img, img_metas=None, **kwargs):
         """Test without augmentation."""
         x = self.extract_feat(img)
 
         try:
-            res = self.head.simple_test(x)
+            if isinstance(self.head, MultiLabelClsHead):
+                assert 'softmax' not in kwargs, (
+                    'Please use `sigmoid` instead of `softmax` '
+                    'in multi-label tasks.')
+            res = self.head.simple_test(x, **kwargs)
         except TypeError as e:
             if 'not tuple' in str(e) and self.return_tuple:
                 return TypeError(