Spaces:
Runtime error
Runtime error
File size: 11,148 Bytes
b334e29 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 |
import torch
import torch.nn.functional as F
from mmdet.core import bbox_overlaps
from ..builder import HEADS
from .retina_head import RetinaHead
EPS = 1e-12
@HEADS.register_module()
class FreeAnchorRetinaHead(RetinaHead):
"""FreeAnchor RetinaHead used in https://arxiv.org/abs/1909.02466.
Args:
num_classes (int): Number of categories excluding the background
category.
in_channels (int): Number of channels in the input feature map.
stacked_convs (int): Number of conv layers in cls and reg tower.
Default: 4.
conv_cfg (dict): dictionary to construct and config conv layer.
Default: None.
norm_cfg (dict): dictionary to construct and config norm layer.
Default: norm_cfg=dict(type='GN', num_groups=32,
requires_grad=True).
pre_anchor_topk (int): Number of boxes that be token in each bag.
bbox_thr (float): The threshold of the saturated linear function. It is
usually the same with the IoU threshold used in NMS.
gamma (float): Gamma parameter in focal loss.
alpha (float): Alpha parameter in focal loss.
""" # noqa: W605
def __init__(self,
num_classes,
in_channels,
stacked_convs=4,
conv_cfg=None,
norm_cfg=None,
pre_anchor_topk=50,
bbox_thr=0.6,
gamma=2.0,
alpha=0.5,
**kwargs):
super(FreeAnchorRetinaHead,
self).__init__(num_classes, in_channels, stacked_convs, conv_cfg,
norm_cfg, **kwargs)
self.pre_anchor_topk = pre_anchor_topk
self.bbox_thr = bbox_thr
self.gamma = gamma
self.alpha = alpha
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]): each item are the truth boxes for each
image in [tl_x, tl_y, br_x, br_y] format.
gt_labels (list[Tensor]): class indices corresponding to each box
img_metas (list[dict]): Meta information of each image, e.g.,
image size, scaling factor, etc.
gt_bboxes_ignore (None | list[Tensor]): specify which bounding
boxes can be ignored when computing the loss.
Returns:
dict[str, Tensor]: A dictionary of loss components.
"""
featmap_sizes = [featmap.size()[-2:] for featmap in cls_scores]
assert len(featmap_sizes) == len(self.anchor_generator.base_anchors)
anchor_list, _ = self.get_anchors(featmap_sizes, img_metas)
anchors = [torch.cat(anchor) for anchor in anchor_list]
# concatenate each level
cls_scores = [
cls.permute(0, 2, 3,
1).reshape(cls.size(0), -1, self.cls_out_channels)
for cls in cls_scores
]
bbox_preds = [
bbox_pred.permute(0, 2, 3, 1).reshape(bbox_pred.size(0), -1, 4)
for bbox_pred in bbox_preds
]
cls_scores = torch.cat(cls_scores, dim=1)
bbox_preds = torch.cat(bbox_preds, dim=1)
cls_prob = torch.sigmoid(cls_scores)
box_prob = []
num_pos = 0
positive_losses = []
for _, (anchors_, gt_labels_, gt_bboxes_, cls_prob_,
bbox_preds_) in enumerate(
zip(anchors, gt_labels, gt_bboxes, cls_prob, bbox_preds)):
with torch.no_grad():
if len(gt_bboxes_) == 0:
image_box_prob = torch.zeros(
anchors_.size(0),
self.cls_out_channels).type_as(bbox_preds_)
else:
# box_localization: a_{j}^{loc}, shape: [j, 4]
pred_boxes = self.bbox_coder.decode(anchors_, bbox_preds_)
# object_box_iou: IoU_{ij}^{loc}, shape: [i, j]
object_box_iou = bbox_overlaps(gt_bboxes_, pred_boxes)
# object_box_prob: P{a_{j} -> b_{i}}, shape: [i, j]
t1 = self.bbox_thr
t2 = object_box_iou.max(
dim=1, keepdim=True).values.clamp(min=t1 + 1e-12)
object_box_prob = ((object_box_iou - t1) /
(t2 - t1)).clamp(
min=0, max=1)
# object_cls_box_prob: P{a_{j} -> b_{i}}, shape: [i, c, j]
num_obj = gt_labels_.size(0)
indices = torch.stack([
torch.arange(num_obj).type_as(gt_labels_), gt_labels_
],
dim=0)
object_cls_box_prob = torch.sparse_coo_tensor(
indices, object_box_prob)
# image_box_iou: P{a_{j} \in A_{+}}, shape: [c, j]
"""
from "start" to "end" implement:
image_box_iou = torch.sparse.max(object_cls_box_prob,
dim=0).t()
"""
# start
box_cls_prob = torch.sparse.sum(
object_cls_box_prob, dim=0).to_dense()
indices = torch.nonzero(box_cls_prob, as_tuple=False).t_()
if indices.numel() == 0:
image_box_prob = torch.zeros(
anchors_.size(0),
self.cls_out_channels).type_as(object_box_prob)
else:
nonzero_box_prob = torch.where(
(gt_labels_.unsqueeze(dim=-1) == indices[0]),
object_box_prob[:, indices[1]],
torch.tensor([
0
]).type_as(object_box_prob)).max(dim=0).values
# upmap to shape [j, c]
image_box_prob = torch.sparse_coo_tensor(
indices.flip([0]),
nonzero_box_prob,
size=(anchors_.size(0),
self.cls_out_channels)).to_dense()
# end
box_prob.append(image_box_prob)
# construct bags for objects
match_quality_matrix = bbox_overlaps(gt_bboxes_, anchors_)
_, matched = torch.topk(
match_quality_matrix,
self.pre_anchor_topk,
dim=1,
sorted=False)
del match_quality_matrix
# matched_cls_prob: P_{ij}^{cls}
matched_cls_prob = torch.gather(
cls_prob_[matched], 2,
gt_labels_.view(-1, 1, 1).repeat(1, self.pre_anchor_topk,
1)).squeeze(2)
# matched_box_prob: P_{ij}^{loc}
matched_anchors = anchors_[matched]
matched_object_targets = self.bbox_coder.encode(
matched_anchors,
gt_bboxes_.unsqueeze(dim=1).expand_as(matched_anchors))
loss_bbox = self.loss_bbox(
bbox_preds_[matched],
matched_object_targets,
reduction_override='none').sum(-1)
matched_box_prob = torch.exp(-loss_bbox)
# positive_losses: {-log( Mean-max(P_{ij}^{cls} * P_{ij}^{loc}) )}
num_pos += len(gt_bboxes_)
positive_losses.append(
self.positive_bag_loss(matched_cls_prob, matched_box_prob))
positive_loss = torch.cat(positive_losses).sum() / max(1, num_pos)
# box_prob: P{a_{j} \in A_{+}}
box_prob = torch.stack(box_prob, dim=0)
# negative_loss:
# \sum_{j}{ FL((1 - P{a_{j} \in A_{+}}) * (1 - P_{j}^{bg})) } / n||B||
negative_loss = self.negative_bag_loss(cls_prob, box_prob).sum() / max(
1, num_pos * self.pre_anchor_topk)
# avoid the absence of gradients in regression subnet
# when no ground-truth in a batch
if num_pos == 0:
positive_loss = bbox_preds.sum() * 0
losses = {
'positive_bag_loss': positive_loss,
'negative_bag_loss': negative_loss
}
return losses
def positive_bag_loss(self, matched_cls_prob, matched_box_prob):
"""Compute positive bag loss.
:math:`-log( Mean-max(P_{ij}^{cls} * P_{ij}^{loc}) )`.
:math:`P_{ij}^{cls}`: matched_cls_prob, classification probability of matched samples.
:math:`P_{ij}^{loc}`: matched_box_prob, box probability of matched samples.
Args:
matched_cls_prob (Tensor): Classification probabilty of matched
samples in shape (num_gt, pre_anchor_topk).
matched_box_prob (Tensor): BBox probability of matched samples,
in shape (num_gt, pre_anchor_topk).
Returns:
Tensor: Positive bag loss in shape (num_gt,).
""" # noqa: E501, W605
# bag_prob = Mean-max(matched_prob)
matched_prob = matched_cls_prob * matched_box_prob
weight = 1 / torch.clamp(1 - matched_prob, 1e-12, None)
weight /= weight.sum(dim=1).unsqueeze(dim=-1)
bag_prob = (weight * matched_prob).sum(dim=1)
# positive_bag_loss = -self.alpha * log(bag_prob)
return self.alpha * F.binary_cross_entropy(
bag_prob, torch.ones_like(bag_prob), reduction='none')
def negative_bag_loss(self, cls_prob, box_prob):
"""Compute negative bag loss.
:math:`FL((1 - P_{a_{j} \in A_{+}}) * (1 - P_{j}^{bg}))`.
:math:`P_{a_{j} \in A_{+}}`: Box_probability of matched samples.
:math:`P_{j}^{bg}`: Classification probability of negative samples.
Args:
cls_prob (Tensor): Classification probability, in shape
(num_img, num_anchors, num_classes).
box_prob (Tensor): Box probability, in shape
(num_img, num_anchors, num_classes).
Returns:
Tensor: Negative bag loss in shape (num_img, num_anchors, num_classes).
""" # noqa: E501, W605
prob = cls_prob * (1 - box_prob)
# There are some cases when neg_prob = 0.
# This will cause the neg_prob.log() to be inf without clamp.
prob = prob.clamp(min=EPS, max=1 - EPS)
negative_bag_loss = prob**self.gamma * F.binary_cross_entropy(
prob, torch.zeros_like(prob), reduction='none')
return (1 - self.alpha) * negative_bag_loss
|