[Dygraph] add FCOS-DCN (#2066)

* add fcos dcn mstrain doc and config

* add dcn on resnet and head

* clean code

dygraph/configs/fcos/README.md

@@ -13,6 +13,8 @@ FCOS (Fully Convolutional One-Stage Object Detection) is a fast anchor-free obje
 | 骨架网络        | 网络类型       | 每张GPU图片个数 | 学习率策略 |推理时间(fps) | Box AP |                           下载                          | 配置文件 |
 | :-------------- | :------------- | :-----: | :-----: | :------------: | :-----: | :-----------------------------------------------------: | :-----: |
 | ResNet50-FPN    | FCOS           |    2    |   1x      |     ----     |  39.6  | [下载链接](https://paddlemodels.bj.bcebos.com/object_detection/dygraph/fcos_r50_fpn_1x_coco.pdparams) | [配置文件](https://github.com/PaddlePaddle/PaddleDetection/tree/dygraph/configs/fcos/fcos_r50_fpn_1x_coco.yml) |
+| ResNet50-FPN    | FCOS+DCN       |    2    |   1x      |     ----     |  44.3  | [下载链接](https://paddlemodels.bj.bcebos.com/object_detection/dygraph/fcos_dcn_r50_fpn_1x_coco.pdparams) | [配置文件](https://github.com/PaddlePaddle/PaddleDetection/tree/dygraph/configs/fcos/fcos_dcn_r50_fpn_1x_coco.yml) |
+| ResNet50-FPN    | FCOS+multiscale_train    |    2    |   2x      |     ----     |  42.0  | [下载链接](https://paddlemodels.bj.bcebos.com/object_detection/dygraph/fcos_r50_fpn_multiscale_2x_coco.pdparams) | [配置文件](https://github.com/PaddlePaddle/PaddleDetection/tree/dygraph/configs/fcos/fcos_r50_fpn_multiscale_2x_coco.yml) |
 
 **Notes:**
 

dygraph/configs/fcos/fcos_dcn_r50_fpn_1x_coco.yml

+_BASE_: [
+  '../datasets/coco_detection.yml',
+  '../runtime.yml',
+  '_base_/fcos_r50_fpn.yml',
+  '_base_/optimizer_1x.yml',
+  '_base_/fcos_reader.yml',
+]
+
+weights: output/fcos_dcn_r50_fpn_1x_coco/model_final
+
+ResNet:
+  depth: 50
+  norm_type: bn
+  freeze_at: 0
+  return_idx: [1,2,3]
+  num_stages: 4
+  dcn_v2_stages: [1,2,3]
+
+FCOSHead:
+  fcos_feat:
+    name: FCOSFeat
+    feat_in: 256
+    feat_out: 256
+    num_convs: 4
+    norm_type: "gn"
+    use_dcn: true
+  num_classes: 80
+  fpn_stride: [8, 16, 32, 64, 128]
+  prior_prob: 0.01
+  fcos_loss: FCOSLoss
+  norm_reg_targets: true
+  centerness_on_reg: true

dygraph/configs/fcos/fcos_r50_fpn_multiscale_2x_coco.yml

+_BASE_: [
+  '../datasets/coco_detection.yml',
+  '../runtime.yml',
+  '_base_/fcos_r50_fpn.yml',
+  '_base_/optimizer_1x.yml',
+  '_base_/fcos_reader.yml',
+]
+
+weights: output/fcos_r50_fpn_multiscale_2x_coco/model_final
+
+TrainReader:
+  sample_transforms:
+  - DecodeOp: {}
+  - RandomFlipOp: {prob: 0.5}
+  - NormalizeImageOp: {is_scale: true, mean: [0.485,0.456,0.406], std: [0.229, 0.224,0.225]}
+  - ResizeImage:
+      target_size: [640, 672, 704, 736, 768, 800]
+      max_size: 1333
+      interp: 1
+      use_cv2: true
+  - PermuteOp: {}
+  batch_transforms:
+  - PadBatchOp: {pad_to_stride: 128}
+  - Gt2FCOSTarget:
+      object_sizes_boundary: [64, 128, 256, 512]
+      center_sampling_radius: 1.5
+      downsample_ratios: [8, 16, 32, 64, 128]
+      norm_reg_targets: True
+  batch_size: 2
+  shuffle: true
+  drop_last: true
+
+epoch: 24
+
+LearningRate:
+  base_lr: 0.01
+  schedulers:
+  - !PiecewiseDecay
+    gamma: 0.1
+    milestones: [16, 22]
+  - !LinearWarmup
+    start_factor: 0.3333333333333333
+    steps: 500

dygraph/ppdet/modeling/backbones/resnet.py

@@ -25,6 +25,7 @@ from ppdet.core.workspace import register, serializable
 from paddle.regularizer import L2Decay
 from .name_adapter import NameAdapter
 from numbers import Integral
+from ppdet.modeling.layers import DeformableConvV2
 
 __all__ = ['ResNet', 'Res5Head']
 
@@ -41,12 +42,14 @@ class ConvNormLayer(nn.Layer):
                  norm_decay=0.,
                  freeze_norm=True,
                  lr=1.0,
+                 dcn_v2=False,
                  name=None):
         super(ConvNormLayer, self).__init__()
         assert norm_type in ['bn', 'sync_bn']
         self.norm_type = norm_type
         self.act = act
 
+        if not dcn_v2:
             self.conv = Conv2D(
                 in_channels=ch_in,
                 out_channels=ch_out,
@@ -57,6 +60,18 @@ class ConvNormLayer(nn.Layer):
                 weight_attr=ParamAttr(
                     learning_rate=lr, name=name + "_weights"),
                 bias_attr=False)
+        else:
+            self.conv = DeformableConvV2(
+                in_channels=ch_in,
+                out_channels=ch_out,
+                kernel_size=filter_size,
+                stride=stride,
+                padding=(filter_size - 1) // 2,
+                groups=1,
+                weight_attr=ParamAttr(
+                    learning_rate=lr, name=name + '_weights'),
+                bias_attr=False,
+                name=name)
 
         bn_name = name_adapter.fix_conv_norm_name(name)
         norm_lr = 0. if freeze_norm else lr
@@ -105,7 +120,8 @@ class BottleNeck(nn.Layer):
                  lr=1.0,
                  norm_type='bn',
                  norm_decay=0.,
-                 freeze_norm=True):
+                 freeze_norm=True,
+                 dcn_v2=False):
         super(BottleNeck, self).__init__()
         if variant == 'a':
             stride1, stride2 = stride, 1
@@ -153,6 +169,7 @@ class BottleNeck(nn.Layer):
             norm_decay=norm_decay,
             freeze_norm=freeze_norm,
             lr=lr,
+            dcn_v2=dcn_v2,
             name=conv_name2)
 
         self.branch2c = ConvNormLayer(
@@ -193,7 +210,8 @@ class Blocks(nn.Layer):
                  lr=1.0,
                  norm_type='bn',
                  norm_decay=0.,
-                 freeze_norm=True):
+                 freeze_norm=True,
+                 dcn_v2=False):
         super(Blocks, self).__init__()
 
         self.blocks = []
@@ -213,7 +231,8 @@ class Blocks(nn.Layer):
                     lr=lr,
                     norm_type=norm_type,
                     norm_decay=norm_decay,
-                    freeze_norm=freeze_norm))
+                    freeze_norm=freeze_norm,
+                    dcn_v2=dcn_v2))
             self.blocks.append(block)
 
     def forward(self, inputs):
@@ -238,6 +257,7 @@ class ResNet(nn.Layer):
                  freeze_norm=True,
                  freeze_at=0,
                  return_idx=[0, 1, 2, 3],
+                 dcn_v2_stages=[-1],
                  num_stages=4):
         super(ResNet, self).__init__()
         self.depth = depth
@@ -255,6 +275,11 @@ class ResNet(nn.Layer):
         self.return_idx = return_idx
         self.num_stages = num_stages
 
+        if isinstance(dcn_v2_stages, Integral):
+            dcn_v2_stages = [dcn_v2_stages]
+        assert max(dcn_v2_stages) < num_stages
+        self.dcn_v2_stages = dcn_v2_stages
+
         block_nums = ResNet_cfg[depth]
         na = NameAdapter(self)
 
@@ -304,7 +329,8 @@ class ResNet(nn.Layer):
                     lr=lr_mult,
                     norm_type=norm_type,
                     norm_decay=norm_decay,
-                    freeze_norm=freeze_norm))
+                    freeze_norm=freeze_norm,
+                    dcn_v2=(i in self.dcn_v2_stages)))
             self.res_layers.append(res_layer)
 
     def forward(self, inputs):

dygraph/ppdet/modeling/layers.py

@@ -30,6 +30,7 @@ from ppdet.core.workspace import register, serializable
 from ppdet.py_op.target import generate_rpn_anchor_target, generate_proposal_target, generate_mask_target
 from ppdet.py_op.post_process import bbox_post_process
 from . import ops
+from paddle.vision.ops import DeformConv2D
 
 
 def _to_list(l):
@@ -38,6 +39,77 @@ def _to_list(l):
     return [l]
 
 
+class DeformableConvV2(nn.Layer):
+    def __init__(self,
+                 in_channels,
+                 out_channels,
+                 kernel_size,
+                 stride=1,
+                 padding=0,
+                 dilation=1,
+                 groups=1,
+                 weight_attr=None,
+                 bias_attr=None,
+                 lr_scale=1,
+                 regularizer=None,
+                 name=None):
+        super(DeformableConvV2, self).__init__()
+        self.offset_channel = 2 * kernel_size**2
+        self.mask_channel = kernel_size**2
+
+        if lr_scale == 1 and regularizer is None:
+            offset_bias_attr = ParamAttr(
+                initializer=Constant(0.),
+                name='{}._conv_offset.bias'.format(name))
+        else:
+            offset_bias_attr = ParamAttr(
+                initializer=Constant(0.),
+                learning_rate=lr_scale,
+                regularizer=regularizer,
+                name='{}._conv_offset.bias'.format(name))
+        self.conv_offset = nn.Conv2D(
+            in_channels,
+            3 * kernel_size**2,
+            kernel_size,
+            stride=stride,
+            padding=(kernel_size - 1) // 2,
+            weight_attr=ParamAttr(
+                initializer=Constant(0.0),
+                name='{}._conv_offset.weight'.format(name)),
+            bias_attr=offset_bias_attr)
+
+        if bias_attr:
+            # in FCOS-DCN head, specifically need learning_rate and regularizer
+            dcn_bias_attr = ParamAttr(
+                name=name + "_bias",
+                initializer=Constant(value=0),
+                regularizer=L2Decay(0.),
+                learning_rate=2.)
+        else:
+            # in ResNet backbone, do not need bias
+            dcn_bias_attr = False
+        self.conv_dcn = DeformConv2D(
+            in_channels,
+            out_channels,
+            kernel_size,
+            stride=stride,
+            padding=(kernel_size - 1) // 2 * dilation,
+            dilation=dilation,
+            groups=groups,
+            weight_attr=weight_attr,
+            bias_attr=dcn_bias_attr)
+
+    def forward(self, x):
+        offset_mask = self.conv_offset(x)
+        offset, mask = paddle.split(
+            offset_mask,
+            num_or_sections=[self.offset_channel, self.mask_channel],
+            axis=1)
+        mask = F.sigmoid(mask)
+        y = self.conv_dcn(x, offset, mask=mask)
+        return y
+
+
 class ConvNormLayer(nn.Layer):
     def __init__(self,
                  ch_in,
@@ -62,6 +134,7 @@ class ConvNormLayer(nn.Layer):
         else:
             bias_attr = False
 
+        if not use_dcn:
             self.conv = nn.Conv2D(
                 in_channels=ch_in,
                 out_channels=ch_out,
@@ -75,6 +148,24 @@ class ConvNormLayer(nn.Layer):
                         mean=0., std=0.01),
                     learning_rate=1.),
                 bias_attr=bias_attr)
+        else:
+            # in FCOS-DCN head, specifically need learning_rate and regularizer
+            self.conv = DeformableConvV2(
+                in_channels=ch_in,
+                out_channels=ch_out,
+                kernel_size=filter_size,
+                stride=stride,
+                padding=(filter_size - 1) // 2,
+                groups=1,
+                weight_attr=ParamAttr(
+                    name=name + "_weight",
+                    initializer=Normal(
+                        mean=0., std=0.01),
+                    learning_rate=1.),
+                bias_attr=True,
+                lr_scale=2.,
+                regularizer=L2Decay(0.),
+                name=name)
 
         param_attr = ParamAttr(
             name=norm_name + "_scale",