[Enhancement]: Refactor SSD

configs/_base_/models/ssd300.py

@@ -5,14 +5,18 @@
     pretrained='open-mmlab://vgg16_caffe',
     backbone=dict(
         type='SSDVGG',
-        input_size=input_size,
         depth=16,
         with_last_pool=False,
         ceil_mode=True,
         out_indices=(3, 4),
-        out_feature_indices=(22, 34),
+        out_feature_indices=(22, 34)),
+    neck=dict(
+        type='SSDNeck',
+        in_channels=(512, 1024),
+        out_channels=(512, 1024, 512, 256, 256, 256),
+        level_strides=(2, 2, 1, 1),
+        level_paddings=(1, 1, 0, 0),
         l2_norm_scale=20),
-    neck=None,
     bbox_head=dict(
         type='SSDHead',
         in_channels=(512, 1024, 512, 256, 256, 256),

configs/pascal_voc/ssd512_voc0712.py

@@ -1,7 +1,6 @@
 _base_ = 'ssd300_voc0712.py'
 input_size = 512
 model = dict(
-    backbone=dict(input_size=input_size),
     bbox_head=dict(
         in_channels=(512, 1024, 512, 256, 256, 256, 256),
         anchor_generator=dict(

configs/ssd/README.md

@@ -17,5 +17,19 @@
 
 | Backbone | Size  | Style | Lr schd | Mem (GB) | Inf time (fps) | box AP | Config | Download |
 | :------: | :---: | :---: | :-----: | :------: | :------------: | :----: | :------: |  :--------: |
-|  VGG16   |  300  | caffe |  120e   |   10.2   |  43.7          |  25.6  | [config](https://github.com/open-mmlab/mmdetection/tree/master/configs/ssd/ssd300_coco.py) | [model](https://download.openmmlab.com/mmdetection/v2.0/ssd/ssd300_coco/ssd300_coco_20200307-a92d2092.pth) | [log](https://download.openmmlab.com/mmdetection/v2.0/ssd/ssd300_coco/ssd300_coco_20200307_174216.log.json) |
-|  VGG16   |  512  | caffe |  120e   |   9.3    |  30.7          |  29.4  | [config](https://github.com/open-mmlab/mmdetection/tree/master/configs/ssd/ssd512_coco.py) | [model](https://download.openmmlab.com/mmdetection/v2.0/ssd/ssd512_coco/ssd512_coco_20200308-038c5591.pth) | [log](https://download.openmmlab.com/mmdetection/v2.0/ssd/ssd512_coco/ssd512_coco_20200308_134447.log.json) |
+|  VGG16   |  300  | caffe |  120e   |   9.9    |  43.7          |  25.9  | [config](https://github.com/open-mmlab/mmdetection/tree/master/configs/ssd/ssd300_coco.py) | [model](https://download.openmmlab.com/mmdetection/v2.0/ssd/ssd300_coco/ssd300_coco_20210604_193052-b61137df.pth) | [log](https://download.openmmlab.com/mmdetection/v2.0/ssd/ssd300_coco/ssd300_coco_20210604_193052.log.json) |
+|  VGG16   |  512  | caffe |  120e   |   19.4   |  30.7          |  29.8  | [config](https://github.com/open-mmlab/mmdetection/tree/master/configs/ssd/ssd512_coco.py) | [model](https://download.openmmlab.com/mmdetection/v2.0/ssd/ssd512_coco/ssd512_coco_20210604_111835-d3eba047.pth) | [log](https://download.openmmlab.com/mmdetection/v2.0/ssd/ssd512_coco/ssd512_coco_20210604_111835.log.json) |
+
+## Notice
+
+In v2.14.0, [PR5291](https://github.com/open-mmlab/mmdetection/pull/5291) refactored SSD neck and head for more
+flexible usage. If users want to use the SSD checkpoint trained in the older versions, we provide a scripts
+`tools/model_converters/upgrade_ssd_version.py` to convert the model weights.
+
+```bash
+python tools/model_converters/upgrade_ssd_version.py ${OLD_MODEL_PATH} ${NEW_MODEL_PATH}
+
+```
+
+- OLD_MODEL_PATH: the path to load the old version SSD model.
+- NEW_MODEL_PATH: the path to save the converted model weights.

configs/ssd/metafile.yml

@@ -16,24 +16,24 @@ Models:
     In Collection: SSD
     Config: configs/ssd/ssd300_coco.py
     Metadata:
-      Training Memory (GB): 10.2
+      Training Memory (GB): 9.9
       inference time (s/im): 0.02288
     Results:
       - Task: Object Detection
         Dataset: COCO
         Metrics:
-          box AP: 25.6
-    Weights: https://download.openmmlab.com/mmdetection/v2.0/ssd/ssd300_coco/ssd300_coco_20200307-a92d2092.pth
+          box AP: 25.9
+    Weights: https://download.openmmlab.com/mmdetection/v2.0/ssd/ssd300_coco/ssd300_coco_20210604_193052-b61137df.pth
 
   - Name: ssd512_coco
     In Collection: SSD
     Config: configs/ssd/ssd512_coco.py
     Metadata:
-      Training Memory (GB): 9.3
+      Training Memory (GB): 19.4
       inference time (s/im): 0.03257
     Results:
       - Task: Object Detection
         Dataset: COCO
         Metrics:
-          box AP: 29.4
-    Weights: https://download.openmmlab.com/mmdetection/v2.0/ssd/ssd512_coco/ssd512_coco_20200308-038c5591.pth
+          box AP: 29.8
+    Weights: https://download.openmmlab.com/mmdetection/v2.0/ssd/ssd512_coco/ssd512_coco_20210604_111835-d3eba047.pth

configs/ssd/ssd512_coco.py

@@ -1,7 +1,11 @@
 _base_ = 'ssd300_coco.py'
 input_size = 512
 model = dict(
-    backbone=dict(input_size=input_size),
+    neck=dict(
+        out_channels=(512, 1024, 512, 256, 256, 256, 256),
+        level_strides=(2, 2, 2, 2, 1),
+        level_paddings=(1, 1, 1, 1, 1),
+        last_kernel_size=4),
     bbox_head=dict(
         in_channels=(512, 1024, 512, 256, 256, 256, 256),
         anchor_generator=dict(

docs/compatibility.md

@@ -1,5 +1,18 @@
 # Compatibility of MMDetection 2.x
 
+## MMDetection 2.14.0
+
+### SSD compatibility
+
+In v2.14.0, to make SSD more flexible to use, [PR5291](https://github.com/open-mmlab/mmdetection/pull/5291) refactored its backbone, neck and head. The users can use the script `tools/model_converters/upgrade_ssd_version.py` to convert their models.
+
+```bash
+python tools/model_converters/upgrade_ssd_version.py ${OLD_MODEL_PATH} ${NEW_MODEL_PATH}
+```
+
+- OLD_MODEL_PATH: the path to load the old version SSD model.
+- NEW_MODEL_PATH: the path to save the converted model weights.
+
 ## MMDetection 2.12.0
 
 MMDetection is going through big refactoring for more general and convenient usages during the releases from v2.12.0 to v2.15.0 (maybe longer).

mmdet/models/backbones/ssd_vgg.py

@@ -1,25 +1,32 @@
 import warnings
 
-import torch
 import torch.nn as nn
-import torch.nn.functional as F
 from mmcv.cnn import VGG
-from mmcv.runner import BaseModule, Sequential
+from mmcv.runner import BaseModule
 
 from ..builder import BACKBONES
+from ..necks import ssd_neck
 
 
 @BACKBONES.register_module()
 class SSDVGG(VGG, BaseModule):
     """VGG Backbone network for single-shot-detection.
 
     Args:
-        input_size (int): width and height of input, from {300, 512}.
         depth (int): Depth of vgg, from {11, 13, 16, 19}.
+        with_last_pool (bool): Whether to add a pooling layer at the last
+            of the model
+        ceil_mode (bool): When True, will use `ceil` instead of `floor`
+            to compute the output shape.
         out_indices (Sequence[int]): Output from which stages.
+        out_feature_indices (Sequence[int]): Output from which feature map.
         pretrained (str, optional): model pretrained path. Default: None
         init_cfg (dict or list[dict], optional): Initialization config dict.
             Default: None
+        input_size (int, optional): Deprecated argumment.
+            Width and height of input, from {300, 512}.
+        l2_norm_scale (float, optional) : Deprecated argumment.
+            L2 normalization layer init scale.
 
     Example:
         >>> self = SSDVGG(input_size=300, depth=11)
@@ -40,23 +47,21 @@ class SSDVGG(VGG, BaseModule):
     }
 
     def __init__(self,
-                 input_size,
                  depth,
                  with_last_pool=False,
                  ceil_mode=True,
                  out_indices=(3, 4),
                  out_feature_indices=(22, 34),
-                 l2_norm_scale=20.,
                  pretrained=None,
-                 init_cfg=None):
+                 init_cfg=None,
+                 input_size=None,
+                 l2_norm_scale=None):
         # TODO: in_channels for mmcv.VGG
         super(SSDVGG, self).__init__(
             depth,
             with_last_pool=with_last_pool,
             ceil_mode=ceil_mode,
             out_indices=out_indices)
-        assert input_size in (300, 512)
-        self.input_size = input_size
 
         self.features.add_module(
             str(len(self.features)),
@@ -72,18 +77,17 @@ def __init__(self,
             str(len(self.features)), nn.ReLU(inplace=True))
         self.out_feature_indices = out_feature_indices
 
-        self.inplanes = 1024
-        self.extra = self._make_extra_layers(self.extra_setting[input_size])
-        self.l2_norm = L2Norm(
-            self.features[out_feature_indices[0] - 1].out_channels,
-            l2_norm_scale)
-
         assert not (init_cfg and pretrained), \
             'init_cfg and pretrained cannot be setting at the same time'
         if isinstance(pretrained, str):
             warnings.warn('DeprecationWarning: pretrained is deprecated, '
                           'please use "init_cfg" instead')
             self.init_cfg = [dict(type='Pretrained', checkpoint=pretrained)]
+        if input_size is not None:
+            warnings.warn('DeprecationWarning: input_size is deprecated')
+        if l2_norm_scale is not None:
+            warnings.warn('DeprecationWarning: l2_norm_scale in VGG is '
+                          'deprecated, it has been moved to SSDNeck.')
         elif pretrained is None:
             if init_cfg is None:
                 self.init_cfg = [
@@ -94,18 +98,6 @@ def __init__(self,
         else:
             raise TypeError('pretrained must be a str or None')
 
-        if init_cfg is None:
-            self.init_cfg += [
-                dict(
-                    type='Xavier',
-                    distribution='uniform',
-                    override=dict(name='extra')),
-                dict(
-                    type='Constant',
-                    val=self.l2_norm.scale,
-                    override=dict(name='l2_norm'))
-            ]
-
     def init_weights(self, pretrained=None):
         super(VGG, self).init_weights()
 
@@ -116,64 +108,17 @@ def forward(self, x):
             x = layer(x)
             if i in self.out_feature_indices:
                 outs.append(x)
-        for i, layer in enumerate(self.extra):
-            x = F.relu(layer(x), inplace=True)
-            if i % 2 == 1:
-                outs.append(x)
-        outs[0] = self.l2_norm(outs[0])
+
         if len(outs) == 1:
             return outs[0]
         else:
             return tuple(outs)
 
-    def _make_extra_layers(self, outplanes):
-        layers = []
-        kernel_sizes = (1, 3)
-        num_layers = 0
-        outplane = None
-        for i in range(len(outplanes)):
-            if self.inplanes == 'S':
-                self.inplanes = outplane
-                continue
-            k = kernel_sizes[num_layers % 2]
-            if outplanes[i] == 'S':
-                outplane = outplanes[i + 1]
-                conv = nn.Conv2d(
-                    self.inplanes, outplane, k, stride=2, padding=1)
-            else:
-                outplane = outplanes[i]
-                conv = nn.Conv2d(
-                    self.inplanes, outplane, k, stride=1, padding=0)
-            layers.append(conv)
-            self.inplanes = outplanes[i]
-            num_layers += 1
-        if self.input_size == 512:
-            layers.append(nn.Conv2d(self.inplanes, 256, 4, padding=1))
-
-        return Sequential(*layers)
 
+class L2Norm(ssd_neck.L2Norm):
 
-class L2Norm(nn.Module):
-
-    def __init__(self, n_dims, scale=20., eps=1e-10):
-        """L2 normalization layer.
-
-        Args:
-            n_dims (int): Number of dimensions to be normalized
-            scale (float, optional): Defaults to 20..
-            eps (float, optional): Used to avoid division by zero.
-                Defaults to 1e-10.
-        """
-        super(L2Norm, self).__init__()
-        self.n_dims = n_dims
-        self.weight = nn.Parameter(torch.Tensor(self.n_dims))
-        self.eps = eps
-        self.scale = scale
-
-    def forward(self, x):
-        """Forward function."""
-        # normalization layer convert to FP32 in FP16 training
-        x_float = x.float()
-        norm = x_float.pow(2).sum(1, keepdim=True).sqrt() + self.eps
-        return (self.weight[None, :, None, None].float().expand_as(x_float) *
-                x_float / norm).type_as(x)
+    def __init__(self, **kwargs):
+        super(L2Norm, self).__init__(**kwargs)
+        warnings.warn('DeprecationWarning: L2Norm in ssd_vgg.py '
+                      'is deprecated, please use L2Norm in '
+                      'mmdet/models/necks/ssd_neck.py instead')