From f7df1eb937c9ba06a77eb54e8b818e9458baa5f1 Mon Sep 17 00:00:00 2001
From: Guanghua Yu <742925032@qq.com>
Date: Fri, 5 Nov 2021 22:29:21 +0800
Subject: [PATCH] Update citation of some code (#4484)

---
 deploy/cpp/src/picodet_postprocess.cc         |   5 +-
 deploy/lite/src/picodet_postprocess.cc        |   5 +-
 ppdet/data/transform/atss_assigner.py         |   3 +
 ppdet/data/transform/batch_operators.py       |   2 +
 ppdet/modeling/assigners/simota_assigner.py   | 223 +++++++++---------
 ppdet/modeling/heads/gfl_head.py              |   3 +
 ppdet/modeling/heads/simota_head.py           | 192 +++++++--------
 ppdet/modeling/heads/solov2_head.py           |   8 +-
 ppdet/modeling/losses/gfocal_loss.py          |   3 +
 ppdet/modeling/losses/varifocal_loss.py       |   3 +
 ppdet/modeling/necks/__init__.py              |   2 -
 ppdet/modeling/necks/csp_pan.py               |   7 +-
 ppdet/modeling/necks/pan.py                   | 127 ----------
 .../modeling/anchor_heads/solov2_head.py      |   3 +
 .../modeling/mask_head/solo_mask_head.py      |   3 +
 15 files changed, 239 insertions(+), 350 deletions(-)
 delete mode 100644 ppdet/modeling/necks/pan.py

diff --git a/deploy/cpp/src/picodet_postprocess.cc b/deploy/cpp/src/picodet_postprocess.cc
index ba73c7d8c..cbe70d43f 100644
--- a/deploy/cpp/src/picodet_postprocess.cc
+++ b/deploy/cpp/src/picodet_postprocess.cc
@@ -11,6 +11,9 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+//
+// The code is based on:
+// https://github.com/RangiLyu/nanodet/blob/main/demo_mnn/nanodet_mnn.cpp
 
 #include "include/picodet_postprocess.h"
 
@@ -124,4 +127,4 @@ void PicoDetPostProcess(std::vector<PaddleDetection::ObjectResult>* results,
   }
 }
 
-}  // namespace PaddleDetection
\ No newline at end of file
+}  // namespace PaddleDetection
diff --git a/deploy/lite/src/picodet_postprocess.cc b/deploy/lite/src/picodet_postprocess.cc
index ba73c7d8c..cbe70d43f 100644
--- a/deploy/lite/src/picodet_postprocess.cc
+++ b/deploy/lite/src/picodet_postprocess.cc
@@ -11,6 +11,9 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+//
+// The code is based on:
+// https://github.com/RangiLyu/nanodet/blob/main/demo_mnn/nanodet_mnn.cpp
 
 #include "include/picodet_postprocess.h"
 
@@ -124,4 +127,4 @@ void PicoDetPostProcess(std::vector<PaddleDetection::ObjectResult>* results,
   }
 }
 
-}  // namespace PaddleDetection
\ No newline at end of file
+}  // namespace PaddleDetection
diff --git a/ppdet/data/transform/atss_assigner.py b/ppdet/data/transform/atss_assigner.py
index d41c85a7e..178d94fb6 100644
--- a/ppdet/data/transform/atss_assigner.py
+++ b/ppdet/data/transform/atss_assigner.py
@@ -12,6 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# The code is based on:
+# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/core/bbox/assigners/atss_assigner.py
+
 from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
diff --git a/ppdet/data/transform/batch_operators.py b/ppdet/data/transform/batch_operators.py
index edc25bead..e43fb7d20 100644
--- a/ppdet/data/transform/batch_operators.py
+++ b/ppdet/data/transform/batch_operators.py
@@ -707,6 +707,8 @@ class Gt2TTFTarget(BaseOperator):
 @register_op
 class Gt2Solov2Target(BaseOperator):
     """Assign mask target and labels in SOLOv2 network.
+    The code of this function is based on:
+        https://github.com/WXinlong/SOLO/blob/master/mmdet/models/anchor_heads/solov2_head.py#L271
     Args:
         num_grids (list): The list of feature map grids size.
         scale_ranges (list): The list of mask boundary range.
diff --git a/ppdet/modeling/assigners/simota_assigner.py b/ppdet/modeling/assigners/simota_assigner.py
index ce22ad7e4..4b34027e3 100644
--- a/ppdet/modeling/assigners/simota_assigner.py
+++ b/ppdet/modeling/assigners/simota_assigner.py
@@ -11,15 +11,13 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-"""
-This code is refer from:
-https://github.com/open-mmlab/mmdetection/blob/master/mmdet/core/bbox/assigners/sim_ota_assigner.py
-"""
+
+# The code is based on:
+# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/core/bbox/assigners/sim_ota_assigner.py
 
 import paddle
 import numpy as np
 import paddle.nn.functional as F
-import paddle.nn as nn
 
 from ppdet.modeling.losses.varifocal_loss import varifocal_loss
 from ppdet.modeling.bbox_utils import batch_bbox_overlaps
@@ -29,7 +27,6 @@ from ppdet.core.workspace import register
 @register
 class SimOTAAssigner(object):
     """Computes matching between predictions and ground truth.
-
     Args:
         center_radius (int | float, optional): Ground truth center size
             to judge whether a prior is in center. Default 2.5.
@@ -58,86 +55,89 @@ class SimOTAAssigner(object):
         self.num_classes = num_classes
         self.use_vfl = use_vfl
 
-    def get_in_gt_and_in_center_info(self, priors, gt_bboxes):
+    def get_in_gt_and_in_center_info(self, flatten_center_and_stride,
+                                     gt_bboxes):
         num_gt = gt_bboxes.shape[0]
 
-        repeated_x = priors[:, 0].unsqueeze(1).tile([1, num_gt])
-        repeated_y = priors[:, 1].unsqueeze(1).tile([1, num_gt])
-        repeated_stride_x = priors[:, 2].unsqueeze(1).tile([1, num_gt])
-        repeated_stride_y = priors[:, 3].unsqueeze(1).tile([1, num_gt])
-
-        # is prior centers in gt bboxes, shape: [n_prior, n_gt]
-        l_ = repeated_x - gt_bboxes[:, 0]
-        t_ = repeated_y - gt_bboxes[:, 1]
-        r_ = gt_bboxes[:, 2] - repeated_x
-        b_ = gt_bboxes[:, 3] - repeated_y
+        flatten_x = flatten_center_and_stride[:, 0].unsqueeze(1).tile(
+            [1, num_gt])
+        flatten_y = flatten_center_and_stride[:, 1].unsqueeze(1).tile(
+            [1, num_gt])
+        flatten_stride_x = flatten_center_and_stride[:, 2].unsqueeze(1).tile(
+            [1, num_gt])
+        flatten_stride_y = flatten_center_and_stride[:, 3].unsqueeze(1).tile(
+            [1, num_gt])
+
+        # is prior centers in gt bboxes, shape: [n_center, n_gt]
+        l_ = flatten_x - gt_bboxes[:, 0]
+        t_ = flatten_y - gt_bboxes[:, 1]
+        r_ = gt_bboxes[:, 2] - flatten_x
+        b_ = gt_bboxes[:, 3] - flatten_y
 
         deltas = paddle.stack([l_, t_, r_, b_], axis=1)
         is_in_gts = deltas.min(axis=1) > 0
         is_in_gts_all = is_in_gts.sum(axis=1) > 0
 
         # is prior centers in gt centers
-        gt_cxs = (gt_bboxes[:, 0] + gt_bboxes[:, 2]) / 2.0
-        gt_cys = (gt_bboxes[:, 1] + gt_bboxes[:, 3]) / 2.0
-        ct_box_l = gt_cxs - self.center_radius * repeated_stride_x
-        ct_box_t = gt_cys - self.center_radius * repeated_stride_y
-        ct_box_r = gt_cxs + self.center_radius * repeated_stride_x
-        ct_box_b = gt_cys + self.center_radius * repeated_stride_y
-
-        cl_ = repeated_x - ct_box_l
-        ct_ = repeated_y - ct_box_t
-        cr_ = ct_box_r - repeated_x
-        cb_ = ct_box_b - repeated_y
+        gt_center_xs = (gt_bboxes[:, 0] + gt_bboxes[:, 2]) / 2.0
+        gt_center_ys = (gt_bboxes[:, 1] + gt_bboxes[:, 3]) / 2.0
+        ct_bound_l = gt_center_xs - self.center_radius * flatten_stride_x
+        ct_bound_t = gt_center_ys - self.center_radius * flatten_stride_y
+        ct_bound_r = gt_center_xs + self.center_radius * flatten_stride_x
+        ct_bound_b = gt_center_ys + self.center_radius * flatten_stride_y
+
+        cl_ = flatten_x - ct_bound_l
+        ct_ = flatten_y - ct_bound_t
+        cr_ = ct_bound_r - flatten_x
+        cb_ = ct_bound_b - flatten_y
 
         ct_deltas = paddle.stack([cl_, ct_, cr_, cb_], axis=1)
         is_in_cts = ct_deltas.min(axis=1) > 0
         is_in_cts_all = is_in_cts.sum(axis=1) > 0
 
-        # in boxes or in centers, shape: [num_priors]
-        is_in_gts_or_centers = paddle.logical_or(is_in_gts_all, is_in_cts_all)
+        # in any of gts or gt centers, shape: [n_center]
+        is_in_gts_or_centers_all = paddle.logical_or(is_in_gts_all,
+                                                     is_in_cts_all)
 
-        is_in_gts_or_centers_inds = paddle.nonzero(
-            is_in_gts_or_centers).squeeze(1)
+        is_in_gts_or_centers_all_inds = paddle.nonzero(
+            is_in_gts_or_centers_all).squeeze(1)
 
-        # both in boxes and centers, shape: [num_fg, num_gt]
-        is_in_boxes_and_centers = paddle.logical_and(
+        # both in gts and gt centers, shape: [num_fg, num_gt]
+        is_in_gts_and_centers = paddle.logical_and(
             paddle.gather(
-                is_in_gts.cast('int'), is_in_gts_or_centers_inds,
+                is_in_gts.cast('int'), is_in_gts_or_centers_all_inds,
                 axis=0).cast('bool'),
             paddle.gather(
-                is_in_cts.cast('int'), is_in_gts_or_centers_inds,
+                is_in_cts.cast('int'), is_in_gts_or_centers_all_inds,
                 axis=0).cast('bool'))
-        return is_in_gts_or_centers, is_in_boxes_and_centers
+        return is_in_gts_or_centers_all, is_in_gts_or_centers_all_inds, is_in_gts_and_centers
 
-    def dynamic_k_matching(self, cost, pairwise_ious, num_gt, valid_mask):
-        matching_matrix = np.zeros_like(cost.numpy())
+    def dynamic_k_matching(self, cost_matrix, pairwise_ious, num_gt):
+        match_matrix = np.zeros_like(cost_matrix.numpy())
         # select candidate topk ious for dynamic-k calculation
         topk_ious, _ = paddle.topk(pairwise_ious, self.candidate_topk, axis=0)
         # calculate dynamic k for each gt
         dynamic_ks = paddle.clip(topk_ious.sum(0).cast('int'), min=1)
         for gt_idx in range(num_gt):
             _, pos_idx = paddle.topk(
-                cost[:, gt_idx], k=dynamic_ks[gt_idx], largest=False)
-            matching_matrix[:, gt_idx][pos_idx.numpy()] = 1.0
+                cost_matrix[:, gt_idx], k=dynamic_ks[gt_idx], largest=False)
+            match_matrix[:, gt_idx][pos_idx.numpy()] = 1.0
 
         del topk_ious, dynamic_ks, pos_idx
 
-        prior_match_gt_mask = matching_matrix.sum(1) > 1
-        if prior_match_gt_mask.sum() > 0:
-            cost = cost.numpy()
-            cost_argmin = np.argmin(cost[prior_match_gt_mask, :], axis=1)
-            matching_matrix[prior_match_gt_mask, :] *= 0.0
-            matching_matrix[prior_match_gt_mask, cost_argmin] = 1.0
-        # get foreground mask inside box and center prior
-        fg_mask_inboxes = matching_matrix.sum(1) > 0.0
-        valid_mask[valid_mask.copy()] = fg_mask_inboxes
+        # match points more than two gts
+        extra_match_gts_mask = match_matrix.sum(1) > 1
+        if extra_match_gts_mask.sum() > 0:
+            cost_matrix = cost_matrix.numpy()
+            cost_argmin = np.argmin(
+                cost_matrix[extra_match_gts_mask, :], axis=1)
+            match_matrix[extra_match_gts_mask, :] *= 0.0
+            match_matrix[extra_match_gts_mask, cost_argmin] = 1.0
+        # get foreground mask
+        match_fg_mask_inmatrix = match_matrix.sum(1) > 0
+        match_gt_inds_to_fg = match_matrix[match_fg_mask_inmatrix, :].argmax(1)
 
-        matched_gt_inds = matching_matrix[fg_mask_inboxes, :].argmax(1)
-
-        matched_gt_inds = paddle.to_tensor(
-            matched_gt_inds, place=pairwise_ious.place)
-
-        return matched_gt_inds, valid_mask
+        return match_gt_inds_to_fg, match_fg_mask_inmatrix
 
     def get_sample(self, assign_gt_inds, gt_bboxes):
         pos_inds = np.unique(np.nonzero(assign_gt_inds > 0)[0])
@@ -155,9 +155,9 @@ class SimOTAAssigner(object):
         return pos_inds, neg_inds, pos_gt_bboxes, pos_assigned_gt_inds
 
     def __call__(self,
-                 pred_scores,
-                 priors,
-                 decoded_bboxes,
+                 flatten_cls_pred_scores,
+                 flatten_center_and_stride,
+                 flatten_bboxes,
                  gt_bboxes,
                  gt_labels,
                  eps=1e-7):
@@ -166,35 +166,31 @@ class SimOTAAssigner(object):
         Returns:
             assign_result: The assigned result.
         """
-
-        INF = 100000000
         num_gt = gt_bboxes.shape[0]
-        num_bboxes = decoded_bboxes.shape[0]
+        num_bboxes = flatten_bboxes.shape[0]
 
-        # assign 0 by default
-        assigned_gt_inds = paddle.full(
-            (num_bboxes, ), 0, dtype=paddle.int64).numpy()
         if num_gt == 0 or num_bboxes == 0:
-            # No ground truth or boxes, return empty assignment
-            priors = priors.numpy()
-            labels = np.ones([num_bboxes], dtype=np.int64) * self.num_classes
-            label_weights = np.ones([num_bboxes], dtype=np.float32)
-            bbox_targets = np.zeros_like(priors)
-            return priors, labels, label_weights, bbox_targets, 0
-
-        valid_mask, is_in_boxes_and_center = self.get_in_gt_and_in_center_info(
-            priors, gt_bboxes)
-
-        valid_mask_inds = paddle.nonzero(valid_mask).squeeze(1)
-        valid_decoded_bbox = decoded_bboxes[valid_mask_inds]
-        valid_pred_scores = pred_scores[valid_mask_inds]
-        num_valid = valid_decoded_bbox.shape[0]
-
-        pairwise_ious = batch_bbox_overlaps(valid_decoded_bbox, gt_bboxes)
+            # No ground truth or boxes
+            label = np.ones([num_bboxes], dtype=np.int64) * self.num_classes
+            label_weight = np.ones([num_bboxes], dtype=np.float32)
+            bbox_target = np.zeros_like(flatten_center_and_stride)
+            return 0, label, label_weight, bbox_target
+
+        is_in_gts_or_centers_all, is_in_gts_or_centers_all_inds, is_in_boxes_and_center = self.get_in_gt_and_in_center_info(
+            flatten_center_and_stride, gt_bboxes)
+
+        # bboxes and scores to calculate matrix
+        valid_flatten_bboxes = flatten_bboxes[is_in_gts_or_centers_all_inds]
+        valid_cls_pred_scores = flatten_cls_pred_scores[
+            is_in_gts_or_centers_all_inds]
+        num_valid_bboxes = valid_flatten_bboxes.shape[0]
+
+        pairwise_ious = batch_bbox_overlaps(valid_flatten_bboxes,
+                                            gt_bboxes)  # [num_points,num_gts]
         if self.use_vfl:
             gt_vfl_labels = gt_labels.squeeze(-1).unsqueeze(0).tile(
-                [num_valid, 1]).reshape([-1])
-            valid_pred_scores = valid_pred_scores.unsqueeze(1).tile(
+                [num_valid_bboxes, 1]).reshape([-1])
+            valid_pred_scores = valid_cls_pred_scores.unsqueeze(1).tile(
                 [1, num_gt, 1]).reshape([-1, self.num_classes])
             vfl_score = np.zeros(valid_pred_scores.shape)
             vfl_score[np.arange(0, vfl_score.shape[0]), gt_vfl_labels.numpy(
@@ -202,64 +198,65 @@ class SimOTAAssigner(object):
             vfl_score = paddle.to_tensor(vfl_score)
             losses_vfl = varifocal_loss(
                 valid_pred_scores, vfl_score,
-                use_sigmoid=False).reshape([num_valid, num_gt])
+                use_sigmoid=False).reshape([num_valid_bboxes, num_gt])
             losses_giou = batch_bbox_overlaps(
-                valid_decoded_bbox, gt_bboxes, mode='giou')
+                valid_flatten_bboxes, gt_bboxes, mode='giou')
             cost_matrix = (
                 losses_vfl * self.cls_weight + losses_giou * self.iou_weight +
-                paddle.logical_not(is_in_boxes_and_center).cast('float32') * INF
-            )
+                paddle.logical_not(is_in_boxes_and_center).cast('float32') *
+                100000000)
         else:
             iou_cost = -paddle.log(pairwise_ious + eps)
             gt_onehot_label = (F.one_hot(
                 gt_labels.squeeze(-1).cast(paddle.int64),
-                pred_scores.shape[-1]).cast('float32').unsqueeze(0).tile(
-                    [num_valid, 1, 1]))
+                flatten_cls_pred_scores.shape[-1]).cast('float32').unsqueeze(0)
+                               .tile([num_valid_bboxes, 1, 1]))
 
-            valid_pred_scores = valid_pred_scores.unsqueeze(1).tile(
+            valid_pred_scores = valid_cls_pred_scores.unsqueeze(1).tile(
                 [1, num_gt, 1])
             cls_cost = F.binary_cross_entropy(
                 valid_pred_scores, gt_onehot_label, reduction='none').sum(-1)
 
             cost_matrix = (
                 cls_cost * self.cls_weight + iou_cost * self.iou_weight +
-                paddle.logical_not(is_in_boxes_and_center).cast('float32') * INF
-            )
+                paddle.logical_not(is_in_boxes_and_center).cast('float32') *
+                100000000)
 
-        matched_gt_inds, valid_mask = \
+        match_gt_inds_to_fg, match_fg_mask_inmatrix = \
             self.dynamic_k_matching(
-                cost_matrix, pairwise_ious, num_gt, valid_mask.numpy())
+                cost_matrix, pairwise_ious, num_gt)
 
-        # assign results
-        gt_labels = gt_labels.numpy()
-        priors = priors.numpy()
-        matched_gt_inds = matched_gt_inds.numpy()
-        gt_bboxes = gt_bboxes.numpy()
+        # sample and assign results
+        assigned_gt_inds = np.zeros([num_bboxes], dtype=np.int64)
+        match_fg_mask_inall = np.zeros_like(assigned_gt_inds)
+        match_fg_mask_inall[is_in_gts_or_centers_all.numpy(
+        )] = match_fg_mask_inmatrix
 
-        assigned_gt_inds[valid_mask] = matched_gt_inds + 1
+        assigned_gt_inds[match_fg_mask_inall.astype(
+            np.bool)] = match_gt_inds_to_fg + 1
 
         pos_inds, neg_inds, pos_gt_bboxes, pos_assigned_gt_inds \
-            = self.get_sample(assigned_gt_inds, gt_bboxes)
+            = self.get_sample(assigned_gt_inds, gt_bboxes.numpy())
 
-        num_cells = priors.shape[0]
-        bbox_targets = np.zeros_like(priors)
-        bbox_weights = np.zeros_like(priors)
-        labels = np.ones([num_cells], dtype=np.int64) * self.num_classes
-        label_weights = np.zeros([num_cells], dtype=np.float32)
+        bbox_target = np.zeros_like(flatten_bboxes)
+        bbox_weight = np.zeros_like(flatten_bboxes)
+        label = np.ones([num_bboxes], dtype=np.int64) * self.num_classes
+        label_weight = np.zeros([num_bboxes], dtype=np.float32)
 
         if len(pos_inds) > 0:
+            gt_labels = gt_labels.numpy()
             pos_bbox_targets = pos_gt_bboxes
-            bbox_targets[pos_inds, :] = pos_bbox_targets
-            bbox_weights[pos_inds, :] = 1.0
+            bbox_target[pos_inds, :] = pos_bbox_targets
+            bbox_weight[pos_inds, :] = 1.0
             if not np.any(gt_labels):
-                labels[pos_inds] = 0
+                label[pos_inds] = 0
             else:
-                labels[pos_inds] = gt_labels.squeeze(-1)[pos_assigned_gt_inds]
+                label[pos_inds] = gt_labels.squeeze(-1)[pos_assigned_gt_inds]
 
-            label_weights[pos_inds] = 1.0
+            label_weight[pos_inds] = 1.0
         if len(neg_inds) > 0:
-            label_weights[neg_inds] = 1.0
+            label_weight[neg_inds] = 1.0
 
         pos_num = max(pos_inds.size, 1)
 
-        return priors, labels, label_weights, bbox_targets, pos_num
+        return pos_num, label, label_weight, bbox_target
diff --git a/ppdet/modeling/heads/gfl_head.py b/ppdet/modeling/heads/gfl_head.py
index e5b0377a6..17e87a4ef 100644
--- a/ppdet/modeling/heads/gfl_head.py
+++ b/ppdet/modeling/heads/gfl_head.py
@@ -12,6 +12,9 @@
 # See the License for the specific language governing permissions and   
 # limitations under the License.
 
+# The code is based on:
+# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/models/dense_heads/gfl_head.py
+
 from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
diff --git a/ppdet/modeling/heads/simota_head.py b/ppdet/modeling/heads/simota_head.py
index 2a870dc13..a1485f390 100644
--- a/ppdet/modeling/heads/simota_head.py
+++ b/ppdet/modeling/heads/simota_head.py
@@ -12,6 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# The code is based on:
+# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/models/dense_heads/yolox_head.py
+
 from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
@@ -30,29 +33,7 @@ from ppdet.core.workspace import register
 from ppdet.modeling.bbox_utils import distance2bbox, bbox2distance
 from ppdet.data.transform.atss_assigner import bbox_overlaps
 
-from .gfl_head import GFLHead, ScaleReg, Integral
-
-
-def multi_apply(func, *args, **kwargs):
-    """Apply function to a list of arguments.
-
-    Note:
-        This function applies the ``func`` to multiple inputs and
-        map the multiple outputs of the ``func`` into different
-        list. Each list contains the same type of outputs corresponding
-        to different inputs.
-
-    Args:
-        func (Function): A function that will be applied to a list of
-            arguments
-
-    Returns:
-        tuple(list): A tuple containing multiple list, each list contains \
-            a kind of returned results by the function
-    """
-    pfunc = partial(func, **kwargs) if kwargs else func
-    map_results = map(pfunc, *args)
-    return tuple(map(list, zip(*map_results)))
+from .gfl_head import GFLHead
 
 
 @register
@@ -123,14 +104,15 @@ class OTAHead(GFLHead):
 
         self.assigner = assigner
 
-    def _get_target_single(self, cls_preds, centors, decoded_bboxes, gt_bboxes,
-                           gt_labels):
+    def _get_target_single(self, flatten_cls_pred, flatten_center_and_stride,
+                           flatten_bbox, gt_bboxes, gt_labels):
         """Compute targets for priors in a single image.
         """
-        centors, labels, label_weights, bbox_targets, pos_num = self.assigner(
-            F.sigmoid(cls_preds), centors, decoded_bboxes, gt_bboxes, gt_labels)
+        pos_num, label, label_weight, bbox_target = self.assigner(
+            F.sigmoid(flatten_cls_pred), flatten_center_and_stride,
+            flatten_bbox, gt_bboxes, gt_labels)
 
-        return (centors, labels, label_weights, bbox_targets, pos_num)
+        return (pos_num, label, label_weight, bbox_target)
 
     def get_loss(self, head_outs, gt_meta):
         cls_scores, bbox_preds = head_outs
@@ -142,26 +124,25 @@ class OTAHead(GFLHead):
                          for featmap in cls_scores]
 
         decode_bbox_preds = []
-        mlvl_centors = []
-        with_stride = True
+        center_and_strides = []
         for featmap_size, stride, bbox_pred in zip(featmap_sizes,
                                                    self.fpn_stride, bbox_preds):
 
+            # center in origin image
             yy, xx = self.get_single_level_center_point(featmap_size, stride,
                                                         self.cell_offset)
-            if with_stride:
-                stride_w = paddle.full((len(xx), ), stride)
-                stride_h = paddle.full((len(yy), ), stride)
-            centers = paddle.stack([xx, yy, stride_w, stride_h], -1).tile(
+
+            center_and_stride = paddle.stack([xx, yy, stride, stride], -1).tile(
                 [num_imgs, 1, 1])
-            mlvl_centors.append(centers)
-            centers_in_feature = centers.reshape([-1, 4])[:, :-2] / stride
+            center_and_strides.append(center_and_stride)
+            center_in_feature = center_and_stride.reshape(
+                [-1, 4])[:, :-2] / stride
             bbox_pred = bbox_pred.transpose([0, 2, 3, 1]).reshape(
                 [num_imgs, -1, 4 * (self.reg_max + 1)])
-            pred_corners = self.distribution_project(bbox_pred)
-            decode_bbox_pred = distance2bbox(
-                centers_in_feature, pred_corners).reshape([num_imgs, -1, 4])
-            decode_bbox_preds.append(decode_bbox_pred * stride)
+            pred_distances = self.distribution_project(bbox_pred)
+            decode_bbox_pred_wo_stride = distance2bbox(
+                center_in_feature, pred_distances).reshape([num_imgs, -1, 4])
+            decode_bbox_preds.append(decode_bbox_pred_wo_stride * stride)
 
         flatten_cls_preds = [
             cls_pred.transpose([0, 2, 3, 1]).reshape(
@@ -170,27 +151,33 @@ class OTAHead(GFLHead):
         ]
         flatten_cls_preds = paddle.concat(flatten_cls_preds, axis=1)
         flatten_bboxes = paddle.concat(decode_bbox_preds, axis=1)
-        flatten_centors = paddle.concat(mlvl_centors, axis=1)
-
-        gt_box, gt_labels = gt_meta['gt_bbox'], gt_meta['gt_class']
-        (centors, labels, label_weights, bbox_targets, pos_num) = multi_apply(
-            self._get_target_single,
-            flatten_cls_preds.detach(),
-            flatten_centors.detach(),
-            flatten_bboxes.detach(), gt_box, gt_labels)
-
-        centors = paddle.to_tensor(np.stack(centors, axis=0))
-        labels = paddle.to_tensor(np.stack(labels, axis=0))
-        label_weights = paddle.to_tensor(np.stack(label_weights, axis=0))
-        bbox_targets = paddle.to_tensor(np.stack(bbox_targets, axis=0))
-
-        centors_list = self._images_to_levels(centors, num_level_anchors)
+        flatten_center_and_strides = paddle.concat(center_and_strides, axis=1)
+
+        gt_boxes, gt_labels = gt_meta['gt_bbox'], gt_meta['gt_class']
+        pos_num_l, label_l, label_weight_l, bbox_target_l = [], [], [], []
+        for flatten_cls_pred,flatten_center_and_stride,flatten_bbox,gt_box, gt_label \
+            in zip(flatten_cls_preds.detach(),flatten_center_and_strides.detach(), \
+                   flatten_bboxes.detach(),gt_boxes, gt_labels):
+            pos_num, label, label_weight, bbox_target = self._get_target_single(
+                flatten_cls_pred, flatten_center_and_stride, flatten_bbox,
+                gt_box, gt_label)
+            pos_num_l.append(pos_num)
+            label_l.append(label)
+            label_weight_l.append(label_weight)
+            bbox_target_l.append(bbox_target)
+
+        labels = paddle.to_tensor(np.stack(label_l, axis=0))
+        label_weights = paddle.to_tensor(np.stack(label_weight_l, axis=0))
+        bbox_targets = paddle.to_tensor(np.stack(bbox_target_l, axis=0))
+
+        center_and_strides_list = self._images_to_levels(
+            flatten_center_and_strides, num_level_anchors)
         labels_list = self._images_to_levels(labels, num_level_anchors)
         label_weights_list = self._images_to_levels(label_weights,
                                                     num_level_anchors)
         bbox_targets_list = self._images_to_levels(bbox_targets,
                                                    num_level_anchors)
-        num_total_pos = sum(pos_num)
+        num_total_pos = sum(pos_num_l)
         try:
             num_total_pos = paddle.distributed.all_reduce(num_total_pos.clone(
             )) / paddle.distributed.get_world_size()
@@ -198,10 +185,10 @@ class OTAHead(GFLHead):
             num_total_pos = max(num_total_pos, 1)
 
         loss_bbox_list, loss_dfl_list, loss_qfl_list, avg_factor = [], [], [], []
-        for cls_score, bbox_pred, grid_cells, labels, label_weights, bbox_targets, stride in zip(
-                cls_scores, bbox_preds, centors_list, labels_list,
+        for cls_score, bbox_pred, center_and_strides, labels, label_weights, bbox_targets, stride in zip(
+                cls_scores, bbox_preds, center_and_strides_list, labels_list,
                 label_weights_list, bbox_targets_list, self.fpn_stride):
-            grid_cells = grid_cells.reshape([-1, 4])
+            center_and_strides = center_and_strides.reshape([-1, 4])
             cls_score = cls_score.transpose([0, 2, 3, 1]).reshape(
                 [-1, self.cls_out_channels])
             bbox_pred = bbox_pred.transpose([0, 2, 3, 1]).reshape(
@@ -219,14 +206,14 @@ class OTAHead(GFLHead):
             if len(pos_inds) > 0:
                 pos_bbox_targets = paddle.gather(bbox_targets, pos_inds, axis=0)
                 pos_bbox_pred = paddle.gather(bbox_pred, pos_inds, axis=0)
-                pos_grid_cell_centers = paddle.gather(
-                    grid_cells[:, :-2], pos_inds, axis=0) / stride
+                pos_centers = paddle.gather(
+                    center_and_strides[:, :-2], pos_inds, axis=0) / stride
 
                 weight_targets = F.sigmoid(cls_score.detach())
                 weight_targets = paddle.gather(
                     weight_targets.max(axis=1, keepdim=True), pos_inds, axis=0)
                 pos_bbox_pred_corners = self.distribution_project(pos_bbox_pred)
-                pos_decode_bbox_pred = distance2bbox(pos_grid_cell_centers,
+                pos_decode_bbox_pred = distance2bbox(pos_centers,
                                                      pos_bbox_pred_corners)
                 pos_decode_bbox_targets = pos_bbox_targets / stride
                 bbox_iou = bbox_overlaps(
@@ -236,7 +223,7 @@ class OTAHead(GFLHead):
                 score[pos_inds.numpy()] = bbox_iou
 
                 pred_corners = pos_bbox_pred.reshape([-1, self.reg_max + 1])
-                target_corners = bbox2distance(pos_grid_cell_centers,
+                target_corners = bbox2distance(pos_centers,
                                                pos_decode_bbox_targets,
                                                self.reg_max).reshape([-1])
                 # regression loss
@@ -355,26 +342,24 @@ class OTAVFLHead(OTAHead):
                          for featmap in cls_scores]
 
         decode_bbox_preds = []
-        mlvl_centors = []
-        with_stride = True
+        center_and_strides = []
         for featmap_size, stride, bbox_pred in zip(featmap_sizes,
                                                    self.fpn_stride, bbox_preds):
-
+            # center in origin image
             yy, xx = self.get_single_level_center_point(featmap_size, stride,
                                                         self.cell_offset)
-            if with_stride:
-                stride_w = paddle.full((len(xx), ), stride)
-                stride_h = paddle.full((len(yy), ), stride)
-            centers = paddle.stack([xx, yy, stride_w, stride_h], -1).tile(
-                [num_imgs, 1, 1])
-            mlvl_centors.append(centers)
-            centers_in_feature = centers.reshape([-1, 4])[:, :-2] / stride
+            strides = paddle.full((len(xx), ), stride)
+            center_and_stride = paddle.stack([xx, yy, strides, strides],
+                                             -1).tile([num_imgs, 1, 1])
+            center_and_strides.append(center_and_stride)
+            center_in_feature = center_and_stride.reshape(
+                [-1, 4])[:, :-2] / stride
             bbox_pred = bbox_pred.transpose([0, 2, 3, 1]).reshape(
                 [num_imgs, -1, 4 * (self.reg_max + 1)])
-            pred_corners = self.distribution_project(bbox_pred)
-            decode_bbox_pred = distance2bbox(
-                centers_in_feature, pred_corners).reshape([num_imgs, -1, 4])
-            decode_bbox_preds.append(decode_bbox_pred * stride)
+            pred_distances = self.distribution_project(bbox_pred)
+            decode_bbox_pred_wo_stride = distance2bbox(
+                center_in_feature, pred_distances).reshape([num_imgs, -1, 4])
+            decode_bbox_preds.append(decode_bbox_pred_wo_stride * stride)
 
         flatten_cls_preds = [
             cls_pred.transpose([0, 2, 3, 1]).reshape(
@@ -383,27 +368,33 @@ class OTAVFLHead(OTAHead):
         ]
         flatten_cls_preds = paddle.concat(flatten_cls_preds, axis=1)
         flatten_bboxes = paddle.concat(decode_bbox_preds, axis=1)
-        flatten_centors = paddle.concat(mlvl_centors, axis=1)
-
-        gt_box, gt_labels = gt_meta['gt_bbox'], gt_meta['gt_class']
-        (centors, labels, label_weights, bbox_targets, pos_num) = multi_apply(
-            self._get_target_single,
-            flatten_cls_preds.detach(),
-            flatten_centors.detach(),
-            flatten_bboxes.detach(), gt_box, gt_labels)
-
-        centors = paddle.to_tensor(np.stack(centors, axis=0))
-        labels = paddle.to_tensor(np.stack(labels, axis=0))
-        label_weights = paddle.to_tensor(np.stack(label_weights, axis=0))
-        bbox_targets = paddle.to_tensor(np.stack(bbox_targets, axis=0))
-
-        centors_list = self._images_to_levels(centors, num_level_anchors)
+        flatten_center_and_strides = paddle.concat(center_and_strides, axis=1)
+
+        gt_boxes, gt_labels = gt_meta['gt_bbox'], gt_meta['gt_class']
+        pos_num_l, label_l, label_weight_l, bbox_target_l = [], [], [], []
+        for flatten_cls_pred, flatten_center_and_stride, flatten_bbox,gt_box,gt_label \
+                in zip(flatten_cls_preds.detach(), flatten_center_and_strides.detach(), \
+                       flatten_bboxes.detach(),gt_boxes,gt_labels):
+            pos_num, label, label_weight, bbox_target = self._get_target_single(
+                flatten_cls_pred, flatten_center_and_stride, flatten_bbox,
+                gt_box, gt_label)
+            pos_num_l.append(pos_num)
+            label_l.append(label)
+            label_weight_l.append(label_weight)
+            bbox_target_l.append(bbox_target)
+
+        labels = paddle.to_tensor(np.stack(label_l, axis=0))
+        label_weights = paddle.to_tensor(np.stack(label_weight_l, axis=0))
+        bbox_targets = paddle.to_tensor(np.stack(bbox_target_l, axis=0))
+
+        center_and_strides_list = self._images_to_levels(
+            flatten_center_and_strides, num_level_anchors)
         labels_list = self._images_to_levels(labels, num_level_anchors)
         label_weights_list = self._images_to_levels(label_weights,
                                                     num_level_anchors)
         bbox_targets_list = self._images_to_levels(bbox_targets,
                                                    num_level_anchors)
-        num_total_pos = sum(pos_num)
+        num_total_pos = sum(pos_num_l)
         try:
             num_total_pos = paddle.distributed.all_reduce(num_total_pos.clone(
             )) / paddle.distributed.get_world_size()
@@ -411,17 +402,16 @@ class OTAVFLHead(OTAHead):
             num_total_pos = max(num_total_pos, 1)
 
         loss_bbox_list, loss_dfl_list, loss_vfl_list, avg_factor = [], [], [], []
-        for cls_score, bbox_pred, grid_cells, labels, label_weights, bbox_targets, stride in zip(
-                cls_scores, bbox_preds, centors_list, labels_list,
+        for cls_score, bbox_pred, center_and_strides, labels, label_weights, bbox_targets, stride in zip(
+                cls_scores, bbox_preds, center_and_strides_list, labels_list,
                 label_weights_list, bbox_targets_list, self.fpn_stride):
-            grid_cells = grid_cells.reshape([-1, 4])
+            center_and_strides = center_and_strides.reshape([-1, 4])
             cls_score = cls_score.transpose([0, 2, 3, 1]).reshape(
                 [-1, self.cls_out_channels])
             bbox_pred = bbox_pred.transpose([0, 2, 3, 1]).reshape(
                 [-1, 4 * (self.reg_max + 1)])
             bbox_targets = bbox_targets.reshape([-1, 4])
             labels = labels.reshape([-1])
-            label_weights = label_weights.reshape([-1])
 
             bg_class_ind = self.num_classes
             pos_inds = paddle.nonzero(
@@ -433,14 +423,14 @@ class OTAVFLHead(OTAHead):
             if len(pos_inds) > 0:
                 pos_bbox_targets = paddle.gather(bbox_targets, pos_inds, axis=0)
                 pos_bbox_pred = paddle.gather(bbox_pred, pos_inds, axis=0)
-                pos_grid_cell_centers = paddle.gather(
-                    grid_cells[:, :-2], pos_inds, axis=0) / stride
+                pos_centers = paddle.gather(
+                    center_and_strides[:, :-2], pos_inds, axis=0) / stride
 
                 weight_targets = F.sigmoid(cls_score.detach())
                 weight_targets = paddle.gather(
                     weight_targets.max(axis=1, keepdim=True), pos_inds, axis=0)
                 pos_bbox_pred_corners = self.distribution_project(pos_bbox_pred)
-                pos_decode_bbox_pred = distance2bbox(pos_grid_cell_centers,
+                pos_decode_bbox_pred = distance2bbox(pos_centers,
                                                      pos_bbox_pred_corners)
                 pos_decode_bbox_targets = pos_bbox_targets / stride
                 bbox_iou = bbox_overlaps(
@@ -453,7 +443,7 @@ class OTAVFLHead(OTAHead):
                 vfl_score[pos_inds.numpy(), pos_labels] = bbox_iou
 
                 pred_corners = pos_bbox_pred.reshape([-1, self.reg_max + 1])
-                target_corners = bbox2distance(pos_grid_cell_centers,
+                target_corners = bbox2distance(pos_centers,
                                                pos_decode_bbox_targets,
                                                self.reg_max).reshape([-1])
                 # regression loss
diff --git a/ppdet/modeling/heads/solov2_head.py b/ppdet/modeling/heads/solov2_head.py
index 355d57e64..6989abb3a 100644
--- a/ppdet/modeling/heads/solov2_head.py
+++ b/ppdet/modeling/heads/solov2_head.py
@@ -34,7 +34,9 @@ __all__ = ['SOLOv2Head']
 @register
 class SOLOv2MaskHead(nn.Layer):
     """
-    MaskHead of SOLOv2
+    MaskHead of SOLOv2.
+    The code of this function is based on:
+        https://github.com/WXinlong/SOLO/blob/master/mmdet/models/mask_heads/mask_feat_head.py
 
     Args:
         in_channels (int): The channel number of input Tensor.
@@ -452,6 +454,10 @@ class SOLOv2Head(nn.Layer):
 
     def get_seg_single(self, cate_preds, seg_preds, kernel_preds, featmap_size,
                        im_shape, scale_factor):
+        """
+        The code of this function is based on:
+            https://github.com/WXinlong/SOLO/blob/master/mmdet/models/anchor_heads/solov2_head.py#L385
+        """
         h = paddle.cast(im_shape[0], 'int32')[0]
         w = paddle.cast(im_shape[1], 'int32')[0]
         upsampled_size_out = [featmap_size[0] * 4, featmap_size[1] * 4]
diff --git a/ppdet/modeling/losses/gfocal_loss.py b/ppdet/modeling/losses/gfocal_loss.py
index 149d30bf8..37e27f084 100644
--- a/ppdet/modeling/losses/gfocal_loss.py
+++ b/ppdet/modeling/losses/gfocal_loss.py
@@ -12,6 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# The code is based on:
+# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/models/losses/gfocal_loss.py
+
 from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
diff --git a/ppdet/modeling/losses/varifocal_loss.py b/ppdet/modeling/losses/varifocal_loss.py
index 07716a016..42d18a659 100644
--- a/ppdet/modeling/losses/varifocal_loss.py
+++ b/ppdet/modeling/losses/varifocal_loss.py
@@ -12,6 +12,9 @@
 # See the License for the specific language governing permissions and   
 # limitations under the License.
 
+# The code is based on:
+# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/models/losses/varifocal_loss.py
+
 from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
diff --git a/ppdet/modeling/necks/__init__.py b/ppdet/modeling/necks/__init__.py
index 79deaf94c..d66697caf 100644
--- a/ppdet/modeling/necks/__init__.py
+++ b/ppdet/modeling/necks/__init__.py
@@ -17,7 +17,6 @@ from . import yolo_fpn
 from . import hrfpn
 from . import ttf_fpn
 from . import centernet_fpn
-from . import pan
 from . import bifpn
 from . import csp_pan
 
@@ -27,6 +26,5 @@ from .hrfpn import *
 from .ttf_fpn import *
 from .centernet_fpn import *
 from .blazeface_fpn import *
-from .pan import *
 from .bifpn import *
 from .csp_pan import *
diff --git a/ppdet/modeling/necks/csp_pan.py b/ppdet/modeling/necks/csp_pan.py
index 6efbb1546..7417c46ab 100644
--- a/ppdet/modeling/necks/csp_pan.py
+++ b/ppdet/modeling/necks/csp_pan.py
@@ -11,10 +11,9 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  
 # See the License for the specific language governing permissions and   
 # limitations under the License.
-"""
-This code is refer from:
-https://github.com/open-mmlab/mmdetection/blob/master/mmdet/models/necks/yolox_pafpn.py
-"""
+
+# The code is based on:
+# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/models/necks/yolox_pafpn.py
 
 import paddle
 import paddle.nn as nn
diff --git a/ppdet/modeling/necks/pan.py b/ppdet/modeling/necks/pan.py
deleted file mode 100644
index 8693f29bd..000000000
--- a/ppdet/modeling/necks/pan.py
+++ /dev/null
@@ -1,127 +0,0 @@
-# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved. 
-#   
-# Licensed under the Apache License, Version 2.0 (the "License");   
-# you may not use this file except in compliance with the License.  
-# You may obtain a copy of the License at   
-#   
-#     http://www.apache.org/licenses/LICENSE-2.0    
-#   
-# Unless required by applicable law or agreed to in writing, software   
-# distributed under the License is distributed on an "AS IS" BASIS, 
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  
-# See the License for the specific language governing permissions and   
-# limitations under the License.
-
-import numpy as np
-import paddle
-import paddle.nn as nn
-import paddle.nn.functional as F
-from paddle import ParamAttr
-from paddle.nn.initializer import XavierUniform
-from paddle.regularizer import L2Decay
-from ppdet.core.workspace import register, serializable
-from ppdet.modeling.layers import ConvNormLayer
-from ..shape_spec import ShapeSpec
-
-__all__ = ['PAN']
-
-
-@register
-@serializable
-class PAN(nn.Layer):
-    """
-    Path Aggregation Network, see https://arxiv.org/abs/1803.01534
-
-    Args:
-        in_channels (list[int]): input channels of each level which can be
-            derived from the output shape of backbone by from_config
-        out_channel (list[int]): output channel of each level
-        spatial_scales (list[float]): the spatial scales between input feature
-            maps and original input image which can be derived from the output
-            shape of backbone by from_config
-        start_level (int): Index of the start input backbone level used to
-            build the feature pyramid. Default: 0.
-        end_level (int): Index of the end input backbone level (exclusive) to
-            build the feature pyramid. Default: -1, which means the last level.
-        norm_type (string|None): The normalization type in FPN module. If
-            norm_type is None, norm will not be used after conv and if
-            norm_type is string, bn, gn, sync_bn are available. default None
-    """
-
-    def __init__(self,
-                 in_channels,
-                 out_channel,
-                 spatial_scales=[0.125, 0.0625, 0.03125],
-                 start_level=0,
-                 end_level=-1,
-                 norm_type=None):
-        super(PAN, self).__init__()
-        self.out_channel = out_channel
-        self.num_ins = len(in_channels)
-        self.spatial_scales = spatial_scales
-        if end_level == -1:
-            self.end_level = self.num_ins
-        else:
-            # if end_level < inputs, no extra level is allowed
-            self.end_level = end_level
-            assert end_level <= len(in_channels)
-        self.start_level = start_level
-        self.norm_type = norm_type
-        self.lateral_convs = []
-
-        for i in range(self.start_level, self.end_level):
-            in_c = in_channels[i - self.start_level]
-            if self.norm_type is not None:
-                lateral = self.add_sublayer(
-                    'pan_lateral' + str(i),
-                    ConvNormLayer(
-                        ch_in=in_c,
-                        ch_out=self.out_channel,
-                        filter_size=1,
-                        stride=1,
-                        norm_type=self.norm_type,
-                        norm_decay=self.norm_decay,
-                        freeze_norm=self.freeze_norm,
-                        initializer=XavierUniform(fan_out=in_c)))
-            else:
-                lateral = self.add_sublayer(
-                    'pan_lateral' + str(i),
-                    nn.Conv2D(
-                        in_channels=in_c,
-                        out_channels=self.out_channel,
-                        kernel_size=1,
-                        weight_attr=ParamAttr(
-                            initializer=XavierUniform(fan_out=in_c))))
-            self.lateral_convs.append(lateral)
-
-    @classmethod
-    def from_config(cls, cfg, input_shape):
-        return {'in_channels': [i.channels for i in input_shape], }
-
-    def forward(self, body_feats):
-        laterals = []
-        for i, lateral_conv in enumerate(self.lateral_convs):
-            laterals.append(lateral_conv(body_feats[i + self.start_level]))
-        num_levels = len(laterals)
-        for i in range(1, num_levels):
-            lvl = num_levels - i
-            upsample = F.interpolate(
-                laterals[lvl],
-                scale_factor=2.,
-                mode='bilinear', )
-            laterals[lvl - 1] += upsample
-
-        outs = [laterals[i] for i in range(num_levels)]
-        for i in range(0, num_levels - 1):
-            outs[i + 1] += F.interpolate(
-                outs[i], scale_factor=0.5, mode='bilinear')
-
-        return outs
-
-    @property
-    def out_shape(self):
-        return [
-            ShapeSpec(
-                channels=self.out_channel, stride=1. / s)
-            for s in self.spatial_scales
-        ]
diff --git a/static/ppdet/modeling/anchor_heads/solov2_head.py b/static/ppdet/modeling/anchor_heads/solov2_head.py
index 74a681f01..6e592695c 100644
--- a/static/ppdet/modeling/anchor_heads/solov2_head.py
+++ b/static/ppdet/modeling/anchor_heads/solov2_head.py
@@ -12,6 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# The code is based on:
+# https://github.com/WXinlong/SOLO/blob/master/mmdet/models/anchor_heads/solov2_head.py
+
 from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
diff --git a/static/ppdet/modeling/mask_head/solo_mask_head.py b/static/ppdet/modeling/mask_head/solo_mask_head.py
index 61e8e2175..0dc439ce1 100644
--- a/static/ppdet/modeling/mask_head/solo_mask_head.py
+++ b/static/ppdet/modeling/mask_head/solo_mask_head.py
@@ -12,6 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# The code is based on:
+# https://github.com/WXinlong/SOLO/blob/master/mmdet/models/mask_heads/mask_feat_head.py
+
 from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
-- 
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