add solov2 enhance model (PaddlePaddle#3517)

* add solov2 enhance model

Author: yghstill

configs/solov2/README.md

@@ -27,6 +27,20 @@ SOLOv2 (Segmenting Objects by Locations) is a fast instance segmentation framewo
 
 - SOLOv2 is trained on COCO train2017 dataset and evaluated on val2017 results of `mAP(IoU=0.5:0.95)`.
 
+## Enhanced model
+| Backbone                | Input size  | Lr schd | V100 FP32(FPS) | Mask AP<sup>val</sup> |         Download                  | Configs |
+| :---------------------: | :-------------------: | :-----: | :------------: | :-----: | :---------: | :------------------------: |
+| Light-R50-VD-DCN-FPN          |  512     |   3x    |     38.6          |  39.0   | [model](https://paddledet.bj.bcebos.com/models/solov2_r50_enhance_coco.pdparams) | [config](https://github.com/PaddlePaddle/PaddleDetection/tree/develop/configs/solov2/solov2_r50_enhance_coco.yml) |
+
+**Optimizing method of enhanced model:**
+- Better backbone network: ResNet50vd-DCN
+- A better pre-training model for knowledge distillation
+- [Exponential Moving Average](https://www.investopedia.com/terms/e/ema.asp)
+- Synchronized Batch Normalization
+- Multi-scale training
+- More data augmentation methods
+- DropBlock
+
 ## Citations
 ```
 @article{wang2020solov2,

configs/solov2/_base_/solov2_light_reader.yml

@@ -0,0 +1,47 @@
+worker_num: 2
+TrainReader:
+  sample_transforms:
+  - Decode: {}
+  - Poly2Mask: {}
+  - RandomDistort: {}
+  - RandomCrop: {}
+  - RandomResize: {interp: 1,
+                     target_size: [[352, 852], [384, 852], [416, 852], [448, 852], [480, 852], [512, 852]],
+                     keep_ratio: True}
+  - RandomFlip: {}
+  - NormalizeImage: {is_scale: true, mean: [0.485,0.456,0.406], std: [0.229, 0.224,0.225]}
+  - Permute: {}
+  batch_transforms:
+  - PadBatch: {pad_to_stride: 32}
+  - Gt2Solov2Target: {num_grids: [40, 36, 24, 16, 12],
+                        scale_ranges: [[1, 96], [48, 192], [96, 384], [192, 768], [384, 2048]],
+                        coord_sigma: 0.2}
+  batch_size: 2
+  shuffle: true
+  drop_last: true
+
+
+EvalReader:
+  sample_transforms:
+  - Decode: {}
+  - NormalizeImage: {is_scale: true, mean: [0.485,0.456,0.406], std: [0.229, 0.224,0.225]}
+  - Resize: {interp: 1, target_size: [512, 852], keep_ratio: True}
+  - Permute: {}
+  batch_transforms:
+  - PadBatch: {pad_to_stride: 32}
+  batch_size: 1
+  shuffle: false
+  drop_last: false
+
+
+TestReader:
+  sample_transforms:
+  - Decode: {}
+  - NormalizeImage: {is_scale: true, mean: [0.485,0.456,0.406], std: [0.229, 0.224,0.225]}
+  - Resize: {interp: 1, target_size: [512, 852], keep_ratio: True}
+  - Permute: {}
+  batch_transforms:
+  - PadBatch: {pad_to_stride: 32}
+  batch_size: 1
+  shuffle: false
+  drop_last: false

configs/solov2/solov2_r50_enhance_coco.yml

@@ -0,0 +1,50 @@
+_BASE_: [
+  '../datasets/coco_instance.yml',
+  '../runtime.yml',
+  '_base_/solov2_r50_fpn.yml',
+  '_base_/optimizer_1x.yml',
+  '_base_/solov2_light_reader.yml',
+]
+pretrain_weights:  https://paddledet.bj.bcebos.com/models/pretrained/ResNet50_vd_ssld_v2_pretrained.pdparams
+weights: output/solov2_r50_fpn_3x_coco/model_final
+epoch: 36
+use_ema: true
+ema_decay: 0.9998
+
+ResNet:
+  depth: 50
+  variant: d
+  freeze_at: 0
+  freeze_norm: false
+  norm_type: sync_bn
+  return_idx: [0,1,2,3]
+  dcn_v2_stages: [1,2,3]
+  lr_mult_list: [0.05, 0.05, 0.1, 0.15]
+  num_stages: 4
+
+SOLOv2Head:
+  seg_feat_channels: 256
+  stacked_convs: 3
+  num_grids: [40, 36, 24, 16, 12]
+  kernel_out_channels: 128
+  solov2_loss: SOLOv2Loss
+  mask_nms: MaskMatrixNMS
+  dcn_v2_stages: [2]
+  drop_block: True
+
+SOLOv2MaskHead:
+  mid_channels: 128
+  out_channels: 128
+  start_level: 0
+  end_level: 3
+  use_dcn_in_tower: True
+
+LearningRate:
+  base_lr: 0.01
+  schedulers:
+  - !PiecewiseDecay
+    gamma: 0.1
+    milestones: [24, 33]
+  - !LinearWarmup
+    start_factor: 0.
+    steps: 1000

ppdet/modeling/heads/solov2_head.py

@@ -22,7 +22,7 @@
 import paddle.nn.functional as F
 from paddle.nn.initializer import Normal, Constant
 
-from ppdet.modeling.layers import ConvNormLayer, MaskMatrixNMS
+from ppdet.modeling.layers import ConvNormLayer, MaskMatrixNMS, DropBlock
 from ppdet.core.workspace import register
 
 from six.moves import zip
@@ -182,7 +182,8 @@ def __init__(self,
                  score_threshold=0.1,
                  mask_threshold=0.5,
                  mask_nms=None,
-                 norm_type='gn'):
+                 norm_type='gn',
+                 drop_block=False):
         super(SOLOv2Head, self).__init__()
         self.num_classes = num_classes
         self.in_channels = in_channels
@@ -198,6 +199,7 @@ def __init__(self,
         self.score_threshold = score_threshold
         self.mask_threshold = mask_threshold
         self.norm_type = norm_type
+        self.drop_block = drop_block
 
         self.kernel_pred_convs = []
         self.cate_pred_convs = []
@@ -250,6 +252,10 @@ def __init__(self,
                 bias_attr=ParamAttr(initializer=Constant(
                     value=float(-np.log((1 - 0.01) / 0.01))))))
 
+        if self.drop_block:
+            self.drop_block_fun = DropBlock(
+                block_size=3, keep_prob=0.9, name='solo_cate.dropblock')
+
     def _points_nms(self, heat, kernel_size=2):
         hmax = F.max_pool2d(heat, kernel_size=kernel_size, stride=1, padding=1)
         keep = paddle.cast((hmax[:, :, :-1, :-1] == heat), 'float32')
@@ -318,10 +324,14 @@ def _get_output_single(self, input, idx):
 
         for kernel_layer in self.kernel_pred_convs:
             kernel_feat = F.relu(kernel_layer(kernel_feat))
+        if self.drop_block:
+            kernel_feat = self.drop_block_fun(kernel_feat)
         kernel_pred = self.solo_kernel(kernel_feat)
         # cate branch
         for cate_layer in self.cate_pred_convs:
             cate_feat = F.relu(cate_layer(cate_feat))
+        if self.drop_block:
+            cate_feat = self.drop_block_fun(cate_feat)
         cate_pred = self.solo_cate(cate_feat)
 
         if not self.training:

ppdet/modeling/layers.py

@@ -250,6 +250,47 @@ def forward(self, inputs):
         return out
 
 
+class DropBlock(nn.Layer):
+    def __init__(self, block_size, keep_prob, name, data_format='NCHW'):
+        """
+        DropBlock layer, see https://arxiv.org/abs/1810.12890
+
+        Args:
+            block_size (int): block size
+            keep_prob (int): keep probability
+            name (str): layer name
+            data_format (str): data format, NCHW or NHWC
+        """
+        super(DropBlock, self).__init__()
+        self.block_size = block_size
+        self.keep_prob = keep_prob
+        self.name = name
+        self.data_format = data_format
+
+    def forward(self, x):
+        if not self.training or self.keep_prob == 1:
+            return x
+        else:
+            gamma = (1. - self.keep_prob) / (self.block_size**2)
+            if self.data_format == 'NCHW':
+                shape = x.shape[2:]
+            else:
+                shape = x.shape[1:3]
+            for s in shape:
+                gamma *= s / (s - self.block_size + 1)
+
+            matrix = paddle.cast(paddle.rand(x.shape, x.dtype) < gamma, x.dtype)
+            mask_inv = F.max_pool2d(
+                matrix,
+                self.block_size,
+                stride=1,
+                padding=self.block_size // 2,
+                data_format=self.data_format)
+            mask = 1. - mask_inv
+            y = x * mask * (mask.numel() / mask.sum())
+            return y
+
+
 @register
 @serializable
 class AnchorGeneratorSSD(object):

ppdet/modeling/necks/yolo_fpn.py

@@ -17,6 +17,7 @@
 import paddle.nn.functional as F
 from paddle import ParamAttr
 from ppdet.core.workspace import register, serializable
+from ppdet.modeling.layers import DropBlock
 from ..backbones.darknet import ConvBNLayer
 from ..shape_spec import ShapeSpec
 
@@ -173,47 +174,6 @@ def forward(self, x):
         return y
 
 
-class DropBlock(nn.Layer):
-    def __init__(self, block_size, keep_prob, name, data_format='NCHW'):
-        """
-        DropBlock layer, see https://arxiv.org/abs/1810.12890
-
-        Args:
-            block_size (int): block size
-            keep_prob (int): keep probability
-            name (str): layer name
-            data_format (str): data format, NCHW or NHWC
-        """
-        super(DropBlock, self).__init__()
-        self.block_size = block_size
-        self.keep_prob = keep_prob
-        self.name = name
-        self.data_format = data_format
-
-    def forward(self, x):
-        if not self.training or self.keep_prob == 1:
-            return x
-        else:
-            gamma = (1. - self.keep_prob) / (self.block_size**2)
-            if self.data_format == 'NCHW':
-                shape = x.shape[2:]
-            else:
-                shape = x.shape[1:3]
-            for s in shape:
-                gamma *= s / (s - self.block_size + 1)
-
-            matrix = paddle.cast(paddle.rand(x.shape, x.dtype) < gamma, x.dtype)
-            mask_inv = F.max_pool2d(
-                matrix,
-                self.block_size,
-                stride=1,
-                padding=self.block_size // 2,
-                data_format=self.data_format)
-            mask = 1. - mask_inv
-            y = x * mask * (mask.numel() / mask.sum())
-            return y
-
-
 class CoordConv(nn.Layer):
     def __init__(self,
                  ch_in,