import torch
from mmcv.runner import force_fp32
from mmdet.core import images_to_levels
from ..builder import HEADS
from ..losses import carl_loss, isr_p
from .retina_head import RetinaHead
[docs]@HEADS.register_module()
class PISARetinaHead(RetinaHead):
"""PISA Retinanet Head.
The head owns the same structure with Retinanet Head, but differs in two
aspects:
1. Importance-based Sample Reweighting Positive (ISR-P) is applied to
change the positive loss weights.
2. Classification-aware regression loss is adopted as a third loss.
"""
[docs] @force_fp32(apply_to=('cls_scores', 'bbox_preds'))
def loss(self,
cls_scores,
bbox_preds,
gt_bboxes,
gt_labels,
img_metas,
gt_bboxes_ignore=None):
"""Compute losses of the head.
Args:
cls_scores (list[Tensor]): Box scores for each scale level
Has shape (N, num_anchors * num_classes, H, W)
bbox_preds (list[Tensor]): Box energies / deltas for each scale
level with shape (N, num_anchors * 4, H, W)
gt_bboxes (list[Tensor]): Ground truth bboxes of each image
with shape (num_obj, 4).
gt_labels (list[Tensor]): Ground truth labels of each image
with shape (num_obj, 4).
img_metas (list[dict]): Meta information of each image, e.g.,
image size, scaling factor, etc.
gt_bboxes_ignore (list[Tensor]): Ignored gt bboxes of each image.
Default: None.
Returns:
dict: Loss dict, comprise classification loss, regression loss and
carl loss.
"""
featmap_sizes = [featmap.size()[-2:] for featmap in cls_scores]
assert len(featmap_sizes) == self.anchor_generator.num_levels
device = cls_scores[0].device
anchor_list, valid_flag_list = self.get_anchors(
featmap_sizes, img_metas, device=device)
label_channels = self.cls_out_channels if self.use_sigmoid_cls else 1
cls_reg_targets = self.get_targets(
anchor_list,
valid_flag_list,
gt_bboxes,
img_metas,
gt_bboxes_ignore_list=gt_bboxes_ignore,
gt_labels_list=gt_labels,
label_channels=label_channels,
return_sampling_results=True)
if cls_reg_targets is None:
return None
(labels_list, label_weights_list, bbox_targets_list, bbox_weights_list,
num_total_pos, num_total_neg, sampling_results_list) = cls_reg_targets
num_total_samples = (
num_total_pos + num_total_neg if self.sampling else num_total_pos)
# anchor number of multi levels
num_level_anchors = [anchors.size(0) for anchors in anchor_list[0]]
# concat all level anchors and flags to a single tensor
concat_anchor_list = []
for i in range(len(anchor_list)):
concat_anchor_list.append(torch.cat(anchor_list[i]))
all_anchor_list = images_to_levels(concat_anchor_list,
num_level_anchors)
num_imgs = len(img_metas)
flatten_cls_scores = [
cls_score.permute(0, 2, 3, 1).reshape(num_imgs, -1, label_channels)
for cls_score in cls_scores
]
flatten_cls_scores = torch.cat(
flatten_cls_scores, dim=1).reshape(-1,
flatten_cls_scores[0].size(-1))
flatten_bbox_preds = [
bbox_pred.permute(0, 2, 3, 1).reshape(num_imgs, -1, 4)
for bbox_pred in bbox_preds
]
flatten_bbox_preds = torch.cat(
flatten_bbox_preds, dim=1).view(-1, flatten_bbox_preds[0].size(-1))
flatten_labels = torch.cat(labels_list, dim=1).reshape(-1)
flatten_label_weights = torch.cat(
label_weights_list, dim=1).reshape(-1)
flatten_anchors = torch.cat(all_anchor_list, dim=1).reshape(-1, 4)
flatten_bbox_targets = torch.cat(
bbox_targets_list, dim=1).reshape(-1, 4)
flatten_bbox_weights = torch.cat(
bbox_weights_list, dim=1).reshape(-1, 4)
# Apply ISR-P
isr_cfg = self.train_cfg.get('isr', None)
if isr_cfg is not None:
all_targets = (flatten_labels, flatten_label_weights,
flatten_bbox_targets, flatten_bbox_weights)
with torch.no_grad():
all_targets = isr_p(
flatten_cls_scores,
flatten_bbox_preds,
all_targets,
flatten_anchors,
sampling_results_list,
bbox_coder=self.bbox_coder,
loss_cls=self.loss_cls,
num_class=self.num_classes,
**self.train_cfg.isr)
(flatten_labels, flatten_label_weights, flatten_bbox_targets,
flatten_bbox_weights) = all_targets
# For convenience we compute loss once instead separating by fpn level,
# so that we don't need to separate the weights by level again.
# The result should be the same
losses_cls = self.loss_cls(
flatten_cls_scores,
flatten_labels,
flatten_label_weights,
avg_factor=num_total_samples)
losses_bbox = self.loss_bbox(
flatten_bbox_preds,
flatten_bbox_targets,
flatten_bbox_weights,
avg_factor=num_total_samples)
loss_dict = dict(loss_cls=losses_cls, loss_bbox=losses_bbox)
# CARL Loss
carl_cfg = self.train_cfg.get('carl', None)
if carl_cfg is not None:
loss_carl = carl_loss(
flatten_cls_scores,
flatten_labels,
flatten_bbox_preds,
flatten_bbox_targets,
self.loss_bbox,
**self.train_cfg.carl,
avg_factor=num_total_pos,
sigmoid=True,
num_class=self.num_classes)
loss_dict.update(loss_carl)
return loss_dict