import mmcv
import torch.nn as nn
import torch.nn.functional as F
from ..builder import LOSSES
from .utils import weighted_loss
@mmcv.jit(derivate=True, coderize=True)
@weighted_loss
def quality_focal_loss(pred, target, beta=2.0):
r"""Quality Focal Loss (QFL) is from `Generalized Focal Loss: Learning
Qualified and Distributed Bounding Boxes for Dense Object Detection
<https://arxiv.org/abs/2006.04388>`_.
Args:
pred (torch.Tensor): Predicted joint representation of classification
and quality (IoU) estimation with shape (N, C), C is the number of
classes.
target (tuple([torch.Tensor])): Target category label with shape (N,)
and target quality label with shape (N,).
beta (float): The beta parameter for calculating the modulating factor.
Defaults to 2.0.
Returns:
torch.Tensor: Loss tensor with shape (N,).
"""
assert len(target) == 2, """target for QFL must be a tuple of two elements,
including category label and quality label, respectively"""
# label denotes the category id, score denotes the quality score
label, score = target
# negatives are supervised by 0 quality score
pred_sigmoid = pred.sigmoid()
scale_factor = pred_sigmoid
zerolabel = scale_factor.new_zeros(pred.shape)
loss = F.binary_cross_entropy_with_logits(
pred, zerolabel, reduction='none') * scale_factor.pow(beta)
# FG cat_id: [0, num_classes -1], BG cat_id: num_classes
bg_class_ind = pred.size(1)
pos = ((label >= 0) & (label < bg_class_ind)).nonzero().squeeze(1)
pos_label = label[pos].long()
# positives are supervised by bbox quality (IoU) score
scale_factor = score[pos] - pred_sigmoid[pos, pos_label]
loss[pos, pos_label] = F.binary_cross_entropy_with_logits(
pred[pos, pos_label], score[pos],
reduction='none') * scale_factor.abs().pow(beta)
loss = loss.sum(dim=1, keepdim=False)
return loss
@mmcv.jit(derivate=True, coderize=True)
@weighted_loss
def distribution_focal_loss(pred, label):
r"""Distribution Focal Loss (DFL) is from `Generalized Focal Loss: Learning
Qualified and Distributed Bounding Boxes for Dense Object Detection
<https://arxiv.org/abs/2006.04388>`_.
Args:
pred (torch.Tensor): Predicted general distribution of bounding boxes
(before softmax) with shape (N, n+1), n is the max value of the
integral set `{0, ..., n}` in paper.
label (torch.Tensor): Target distance label for bounding boxes with
shape (N,).
Returns:
torch.Tensor: Loss tensor with shape (N,).
"""
dis_left = label.long()
dis_right = dis_left + 1
weight_left = dis_right.float() - label
weight_right = label - dis_left.float()
loss = F.cross_entropy(pred, dis_left, reduction='none') * weight_left \
+ F.cross_entropy(pred, dis_right, reduction='none') * weight_right
return loss
[docs]@LOSSES.register_module()
class QualityFocalLoss(nn.Module):
r"""Quality Focal Loss (QFL) is a variant of `Generalized Focal Loss:
Learning Qualified and Distributed Bounding Boxes for Dense Object
Detection <https://arxiv.org/abs/2006.04388>`_.
Args:
use_sigmoid (bool): Whether sigmoid operation is conducted in QFL.
Defaults to True.
beta (float): The beta parameter for calculating the modulating factor.
Defaults to 2.0.
reduction (str): Options are "none", "mean" and "sum".
loss_weight (float): Loss weight of current loss.
"""
def __init__(self,
use_sigmoid=True,
beta=2.0,
reduction='mean',
loss_weight=1.0):
super(QualityFocalLoss, self).__init__()
assert use_sigmoid is True, 'Only sigmoid in QFL supported now.'
self.use_sigmoid = use_sigmoid
self.beta = beta
self.reduction = reduction
self.loss_weight = loss_weight
[docs] def forward(self,
pred,
target,
weight=None,
avg_factor=None,
reduction_override=None):
"""Forward function.
Args:
pred (torch.Tensor): Predicted joint representation of
classification and quality (IoU) estimation with shape (N, C),
C is the number of classes.
target (tuple([torch.Tensor])): Target category label with shape
(N,) and target quality label with shape (N,).
weight (torch.Tensor, optional): The weight of loss for each
prediction. Defaults to None.
avg_factor (int, optional): Average factor that is used to average
the loss. Defaults to None.
reduction_override (str, optional): The reduction method used to
override the original reduction method of the loss.
Defaults to None.
"""
assert reduction_override in (None, 'none', 'mean', 'sum')
reduction = (
reduction_override if reduction_override else self.reduction)
if self.use_sigmoid:
loss_cls = self.loss_weight * quality_focal_loss(
pred,
target,
weight,
beta=self.beta,
reduction=reduction,
avg_factor=avg_factor)
else:
raise NotImplementedError
return loss_cls
[docs]@LOSSES.register_module()
class DistributionFocalLoss(nn.Module):
r"""Distribution Focal Loss (DFL) is a variant of `Generalized Focal Loss:
Learning Qualified and Distributed Bounding Boxes for Dense Object
Detection <https://arxiv.org/abs/2006.04388>`_.
Args:
reduction (str): Options are `'none'`, `'mean'` and `'sum'`.
loss_weight (float): Loss weight of current loss.
"""
def __init__(self, reduction='mean', loss_weight=1.0):
super(DistributionFocalLoss, self).__init__()
self.reduction = reduction
self.loss_weight = loss_weight
[docs] def forward(self,
pred,
target,
weight=None,
avg_factor=None,
reduction_override=None):
"""Forward function.
Args:
pred (torch.Tensor): Predicted general distribution of bounding
boxes (before softmax) with shape (N, n+1), n is the max value
of the integral set `{0, ..., n}` in paper.
target (torch.Tensor): Target distance label for bounding boxes
with shape (N,).
weight (torch.Tensor, optional): The weight of loss for each
prediction. Defaults to None.
avg_factor (int, optional): Average factor that is used to average
the loss. Defaults to None.
reduction_override (str, optional): The reduction method used to
override the original reduction method of the loss.
Defaults to None.
"""
assert reduction_override in (None, 'none', 'mean', 'sum')
reduction = (
reduction_override if reduction_override else self.reduction)
loss_cls = self.loss_weight * distribution_focal_loss(
pred, target, weight, reduction=reduction, avg_factor=avg_factor)
return loss_cls