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# Copyright (c) 2022 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.
# 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
from paddlers.models.ppdet.modeling.losses.varifocal_loss import varifocal_loss
from paddlers.models.ppdet.modeling.bbox_utils import batch_bbox_overlaps
from paddlers.models.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.
candidate_topk (int, optional): The candidate top-k which used to
get top-k ious to calculate dynamic-k. Default 10.
iou_weight (int | float, optional): The scale factor for regression
iou cost. Default 3.0.
cls_weight (int | float, optional): The scale factor for classification
cost. Default 1.0.
num_classes (int): The num_classes of dataset.
use_vfl (int): Whether to use varifocal_loss when calculating the cost matrix.
"""
__shared__ = ['num_classes']
def __init__(self,
center_radius=2.5,
candidate_topk=10,
iou_weight=3.0,
cls_weight=1.0,
num_classes=80,
use_vfl=True):
self.center_radius = center_radius
self.candidate_topk = candidate_topk
self.iou_weight = iou_weight
self.cls_weight = cls_weight
self.num_classes = num_classes
self.use_vfl = use_vfl
def get_in_gt_and_in_center_info(self, flatten_center_and_stride,
gt_bboxes):
num_gt = gt_bboxes.shape[0]
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_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 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_all_inds = paddle.nonzero(
is_in_gts_or_centers_all).squeeze(1)
# 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_all_inds,
axis=0).cast('bool'),
paddle.gather(
is_in_cts.cast('int'), is_in_gts_or_centers_all_inds,
axis=0).cast('bool'))
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_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_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
# 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)
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])
neg_inds = np.unique(np.nonzero(assign_gt_inds == 0)[0])
pos_assigned_gt_inds = assign_gt_inds[pos_inds] - 1
if gt_bboxes.size == 0:
# hack for index error case
assert pos_assigned_gt_inds.size == 0
pos_gt_bboxes = np.empty_like(gt_bboxes).reshape(-1, 4)
else:
if len(gt_bboxes.shape) < 2:
gt_bboxes = gt_bboxes.resize(-1, 4)
pos_gt_bboxes = gt_bboxes[pos_assigned_gt_inds, :]
return pos_inds, neg_inds, pos_gt_bboxes, pos_assigned_gt_inds
def __call__(self,
flatten_cls_pred_scores,
flatten_center_and_stride,
flatten_bboxes,
gt_bboxes,
gt_labels,
eps=1e-7):
"""Assign gt to priors using SimOTA.
TODO: add comment.
Returns:
assign_result: The assigned result.
"""
num_gt = gt_bboxes.shape[0]
num_bboxes = flatten_bboxes.shape[0]
if num_gt == 0 or num_bboxes == 0:
# 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_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(
)] = pairwise_ious.reshape([-1])
vfl_score = paddle.to_tensor(vfl_score)
losses_vfl = varifocal_loss(
valid_pred_scores, vfl_score,
use_sigmoid=False).reshape([num_valid_bboxes, num_gt])
losses_giou = batch_bbox_overlaps(
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') *
100000000)
else:
iou_cost = -paddle.log(pairwise_ious + eps)
gt_onehot_label = (F.one_hot(
gt_labels.squeeze(-1).cast(paddle.int64),
flatten_cls_pred_scores.shape[-1]).cast('float32').unsqueeze(0)
.tile([num_valid_bboxes, 1, 1]))
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') *
100000000)
match_gt_inds_to_fg, match_fg_mask_inmatrix = \
self.dynamic_k_matching(
cost_matrix, pairwise_ious, num_gt)
# 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[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.numpy())
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_target[pos_inds, :] = pos_bbox_targets
bbox_weight[pos_inds, :] = 1.0
if not np.any(gt_labels):
label[pos_inds] = 0
else:
label[pos_inds] = gt_labels.squeeze(-1)[pos_assigned_gt_inds]
label_weight[pos_inds] = 1.0
if len(neg_inds) > 0:
label_weight[neg_inds] = 1.0
pos_num = max(pos_inds.size, 1)
return pos_num, label, label_weight, bbox_target