def forward(self, anchors, objectness, box_regression, targets=None):
"""
Arguments:
anchors: list[list[BoxList]]
objectness: list[tensor]
box_regression: list[tensor]
Returns:
boxlists (list[BoxList]): the post-processed anchors, after
applying box decoding and NMS
"""
sampled_boxes = []
num_levels = len(objectness)
anchors = list(zip(*anchors))
for a, o, b in zip(anchors, objectness, box_regression):
sampled_boxes.append(self.forward_for_single_feature_map(a, o, b))
boxlists = list(zip(*sampled_boxes))
boxlists = [cat_boxlist(boxlist) for boxlist in boxlists]
if num_levels > 1:
boxlists = self.select_over_all_levels(boxlists)
# append ground-truth bboxes to proposals
if self.training and targets is not None:
boxlists = self.add_gt_proposals(boxlists, targets)
return boxlists
def cat_boxlist_with_keypoints(boxlists):
assert all(boxlist.has_field("keypoints") for boxlist in boxlists)
kp = [boxlist.get_field("keypoints").keypoints for boxlist in boxlists]
kp = cat(kp, 0)
fields = boxlists[0].get_fields()
fields = [field for field in fields if field != "keypoints"]
boxlists = [boxlist.copy_with_fields(fields) for boxlist in boxlists]
boxlists = cat_boxlist(boxlists)
boxlists.add_field("keypoints", kp)
return boxlists
def forward(self, box_cls, box_regression, centerness, anchors):
sampled_boxes = []
anchors = list(zip(*anchors))
for _, (o, b, c, a) in enumerate(
zip(box_cls, box_regression, centerness, anchors)):
sampled_boxes.append(
self.forward_for_single_feature_map(o, b, c, a))
boxlists = list(zip(*sampled_boxes))
boxlists = [cat_boxlist(boxlist) for boxlist in boxlists]
if not (self.bbox_aug_enabled and not self.bbox_aug_vote):
boxlists = self.select_over_all_levels(boxlists)
return boxlists
def select_over_all_levels(self, boxlists):
num_images = len(boxlists)
results = []
for i in range(num_images):
scores = boxlists[i].get_field("scores")
labels = boxlists[i].get_field("labels")
boxes = boxlists[i].bbox
boxlist = boxlists[i]
result = []
# skip the background
for j in range(1, self.num_classes):
inds = (labels == j).nonzero().view(-1)
scores_j = scores[inds]
boxes_j = boxes[inds, :].view(-1, 4)
boxlist_for_class = BoxList(boxes_j, boxlist.size, mode="xyxy")
boxlist_for_class.add_field("scores", scores_j)
boxlist_for_class = boxlist_nms(boxlist_for_class,
self.nms_thresh,
score_field="scores")
num_labels = len(boxlist_for_class)
boxlist_for_class.add_field(
"labels",
torch.full((num_labels, ),
j,
dtype=torch.int64,
device=scores.device))
result.append(boxlist_for_class)
result = cat_boxlist(result)
number_of_detections = len(result)
# Limit to max_per_image detections **over all classes**
if number_of_detections > self.fpn_post_nms_top_n > 0:
cls_scores = result.get_field("scores")
image_thresh, _ = torch.kthvalue(
cls_scores.cpu(),
number_of_detections - self.fpn_post_nms_top_n + 1)
keep = cls_scores >= image_thresh.item()
keep = torch.nonzero(keep).squeeze(1)
result = result[keep]
results.append(result)
return results
def filter_results(self, boxlist, num_classes):
"""Returns bounding-box detection results by thresholding on scores and
applying non-maximum suppression (NMS).
"""
# unwrap the boxlist to avoid additional overhead.
# if we had multi-class NMS, we could perform this directly on the boxlist
boxes = boxlist.bbox.reshape(-1, num_classes * 4)
scores = boxlist.get_field("scores").reshape(-1, num_classes)
device = scores.device
result = []
# Apply threshold on detection probabilities and apply NMS
# Skip j = 0, because it's the background class
inds_all = scores > self.score_thresh
for j in range(1, num_classes):
inds = inds_all[:, j].nonzero().squeeze(1)
scores_j = scores[inds, j]
boxes_j = boxes[inds, j * 4:(j + 1) * 4]
boxlist_for_class = BoxList(boxes_j, boxlist.size, mode="xyxy")
boxlist_for_class.add_field("scores", scores_j)
boxlist_for_class = boxlist_nms(boxlist_for_class, self.nms)
num_labels = len(boxlist_for_class)
boxlist_for_class.add_field(
"labels",
torch.full((num_labels, ), j, dtype=torch.int64,
device=device))
result.append(boxlist_for_class)
result = cat_boxlist(result)
number_of_detections = len(result)
# Limit to max_per_image detections **over all classes**
if number_of_detections > self.detections_per_img > 0:
cls_scores = result.get_field("scores")
image_thresh, _ = torch.kthvalue(
cls_scores.cpu(),
number_of_detections - self.detections_per_img + 1)
keep = cls_scores >= image_thresh.item()
keep = torch.nonzero(keep).squeeze(1)
result = result[keep]
return result
def __call__(self, anchors, objectness, box_regression, targets):
"""
Arguments:
anchors (list[BoxList])
objectness (list[Tensor])
box_regression (list[Tensor])
targets (list[BoxList])
Returns:
objectness_loss (Tensor)
box_loss (Tensor
"""
anchors = [cat_boxlist(anchors_per_image) for anchors_per_image in anchors]
labels, regression_targets = self.prepare_targets(anchors, targets)
sampled_pos_inds, sampled_neg_inds = self.fg_bg_sampler(labels)
sampled_pos_inds = torch.nonzero(torch.cat(sampled_pos_inds, dim=0)).squeeze(1)
sampled_neg_inds = torch.nonzero(torch.cat(sampled_neg_inds, dim=0)).squeeze(1)
sampled_inds = torch.cat([sampled_pos_inds, sampled_neg_inds], dim=0)
objectness, box_regression = \
concat_box_prediction_layers(objectness, box_regression)
objectness = objectness.squeeze()
labels = torch.cat(labels, dim=0)
regression_targets = torch.cat(regression_targets, dim=0)
box_loss = smooth_l1_loss(
box_regression[sampled_pos_inds],
regression_targets[sampled_pos_inds],
beta=1.0 / 9,
size_average=False,
) / (sampled_inds.numel())
objectness_loss = F.binary_cross_entropy_with_logits(
objectness[sampled_inds], labels[sampled_inds]
)
return objectness_loss, box_loss
def prepare_iou_based_targets(self, targets, anchors):
"""Compute IoU-based targets"""
cls_labels = []
reg_targets = []
matched_idx_all = []
for im_i in range(len(targets)):
targets_per_im = targets[im_i]
assert targets_per_im.mode == "xyxy"
bboxes_per_im = targets_per_im.bbox
labels_per_im = targets_per_im.get_field("labels")
anchors_per_im = cat_boxlist(anchors[im_i])
num_gt = bboxes_per_im.shape[0]
match_quality_matrix = boxlist_iou(targets_per_im, anchors_per_im)
matched_idxs = self.matcher(match_quality_matrix)
targets_per_im = targets_per_im.copy_with_fields(['labels'])
matched_targets = targets_per_im[matched_idxs.clamp(min=0)]
cls_labels_per_im = matched_targets.get_field("labels")
cls_labels_per_im = cls_labels_per_im.to(dtype=torch.float32)
# Background (negative examples)
bg_indices = matched_idxs == Matcher.BELOW_LOW_THRESHOLD
cls_labels_per_im[bg_indices] = 0
# discard indices that are between thresholds
inds_to_discard = matched_idxs == Matcher.BETWEEN_THRESHOLDS
cls_labels_per_im[inds_to_discard] = -1
matched_gts = matched_targets.bbox
matched_idx_all.append(matched_idxs.view(1, -1))
reg_targets_per_im = self.box_coder.encode(matched_gts,
anchors_per_im.bbox)
cls_labels.append(cls_labels_per_im)
reg_targets.append(reg_targets_per_im)
return cls_labels, reg_targets, matched_idx_all
def merge_result_from_multi_scales(boxlists, nms_type='nms', vote_thresh=0.65):
num_images = len(boxlists)
results = []
for i in range(num_images):
scores = boxlists[i].get_field("scores")
labels = boxlists[i].get_field("labels")
boxes = boxlists[i].bbox
boxlist = boxlists[i]
result = []
# skip the background
for j in range(1, cfg.MODEL.RETINANET.NUM_CLASSES):
inds = (labels == j).nonzero().view(-1)
scores_j = scores[inds]
boxes_j = boxes[inds, :].view(-1, 4)
boxlist_for_class = BoxList(boxes_j, boxlist.size, mode="xyxy")
boxlist_for_class.add_field("scores", scores_j)
boxlist_for_class = boxlist_nms(boxlist_for_class, cfg.MODEL.ATSS.NMS_TH, score_field="scores",
nms_type=nms_type, vote_thresh=vote_thresh)
num_labels = len(boxlist_for_class)
boxlist_for_class.add_field("labels", torch.full((num_labels,), j, dtype=torch.int64, device=scores.device))
result.append(boxlist_for_class)
result = cat_boxlist(result)
number_of_detections = len(result)
# Limit to max_per_image detections **over all classes**
if number_of_detections > cfg.MODEL.ATSS.PRE_NMS_TOP_N > 0:
cls_scores = result.get_field("scores")
image_thresh, _ = torch.kthvalue(
cls_scores.cpu(),
number_of_detections - cfg.MODEL.ATSS.PRE_NMS_TOP_N + 1
)
keep = cls_scores >= image_thresh.item()
keep = torch.nonzero(keep).squeeze(1)
result = result[keep]
results.append(result)
return results
def add_gt_proposals(self, proposals, targets):
"""
Arguments:
proposals: list[BoxList]
targets: list[BoxList]
"""
# Get the device we're operating on
device = proposals[0].bbox.device
gt_boxes = [target.copy_with_fields([]) for target in targets]
# later cat of bbox requires all fields to be present for all bbox
# so we need to add a dummy for objectness that's missing
for gt_box in gt_boxes:
gt_box.add_field("objectness",
torch.ones(len(gt_box), device=device))
proposals = [
cat_boxlist((proposal, gt_box))
for proposal, gt_box in zip(proposals, gt_boxes)
]
return proposals
def forward(self, locations, box_cls, box_regression, centerness,
image_sizes):
"""
Arguments:
anchors: list[list[BoxList]]
box_cls: list[tensor]
box_regression: list[tensor]
image_sizes: list[(h, w)]
Returns:
boxlists (list[BoxList]): the post-processed anchors, after
applying box decoding and NMS
"""
sampled_boxes = []
for _, (l, o, b, c) in enumerate(
zip(locations, box_cls, box_regression, centerness)):
sampled_boxes.append(
self.forward_for_single_feature_map(l, o, b, c, image_sizes))
boxlists = list(zip(*sampled_boxes))
boxlists = [cat_boxlist(boxlist) for boxlist in boxlists]
if not self.bbox_aug_enabled:
boxlists = self.select_over_all_levels(boxlists)
return boxlists
def __call__(self, box_cls, box_regression, centerness, targets, anchors):
labels, reg_targets = self.prepare_targets(targets, anchors)
N = len(labels)
box_cls_flatten, box_regression_flatten = concat_box_prediction_layers(box_cls, box_regression)
centerness_flatten = [ct.permute(0, 2, 3, 1).reshape(N, -1, 1) for ct in centerness]
centerness_flatten = torch.cat(centerness_flatten, dim=1).reshape(-1)
labels_flatten = torch.cat(labels, dim=0)
reg_targets_flatten = torch.cat(reg_targets, dim=0)
anchors_flatten = torch.cat([cat_boxlist(anchors_per_image).bbox for anchors_per_image in anchors], dim=0)
pos_inds = torch.nonzero(labels_flatten > 0).squeeze(1)
num_gpus = get_num_gpus()
total_num_pos = reduce_sum(pos_inds.new_tensor([pos_inds.numel()])).item()
num_pos_avg_per_gpu = max(total_num_pos / float(num_gpus), 1.0)
cls_loss = self.cls_loss_func(box_cls_flatten, labels_flatten.int()) / num_pos_avg_per_gpu
if pos_inds.numel() > 0:
box_regression_flatten = box_regression_flatten[pos_inds]
reg_targets_flatten = reg_targets_flatten[pos_inds]
anchors_flatten = anchors_flatten[pos_inds]
centerness_flatten = centerness_flatten[pos_inds]
centerness_targets = self.compute_centerness_targets(reg_targets_flatten, anchors_flatten)
sum_centerness_targets_avg_per_gpu = reduce_sum(centerness_targets.sum()).item() / float(num_gpus)
reg_loss = self.GIoULoss(box_regression_flatten, reg_targets_flatten, anchors_flatten,
weight=centerness_targets) / sum_centerness_targets_avg_per_gpu
centerness_loss = self.centerness_loss_func(centerness_flatten, centerness_targets) / num_pos_avg_per_gpu
else:
reg_loss = box_regression_flatten.sum()
centerness_loss = reg_loss * 0
return cls_loss, reg_loss * self.cfg.MODEL.ATSS.REG_LOSS_WEIGHT, centerness_loss
def __call__(self, box_cls, box_regression, iou_pred, targets, anchors, locations):
# get IoU-based anchor assignment first to compute anchor scores
(iou_based_labels,
iou_based_reg_targets,
matched_idx_all) = self.prepare_iou_based_targets(targets, anchors)
matched_idx_all = torch.cat(matched_idx_all, dim=0)
N = len(iou_based_labels)
iou_based_labels_flatten = torch.cat(iou_based_labels, dim=0).int()
iou_based_reg_targets_flatten = torch.cat(iou_based_reg_targets, dim=0)
box_cls_flatten, box_regression_flatten = concat_box_prediction_layers(
box_cls, box_regression)
anchors_flatten = torch.cat([cat_boxlist(anchors_per_image).bbox
for anchors_per_image in anchors], dim=0)
if iou_pred is not None:
iou_pred_flatten = [ip.permute(0, 2, 3, 1).reshape(N, -1, 1) for ip in iou_pred]
iou_pred_flatten = torch.cat(iou_pred_flatten, dim=1).reshape(-1)
pos_inds = torch.nonzero(iou_based_labels_flatten > 0).squeeze(1)
if pos_inds.numel() > 0:
n_anchors = box_regression[0].shape[1] // 4
n_loss_per_box = 1 if 'iou' in self.reg_loss_type else 4
# compute anchor scores (losses) for all anchors
iou_based_cls_loss = self.cls_loss_func(box_cls_flatten.detach(),
iou_based_labels_flatten,
sum=False)
iou_based_reg_loss = self.compute_reg_loss(iou_based_reg_targets_flatten,
box_regression_flatten.detach(),
anchors_flatten,
iou_based_labels_flatten,
locations,
n_anchors,
weights=None,
N=N)
iou_based_reg_loss_full = torch.full((iou_based_cls_loss.shape[0],),
fill_value=INF,
device=iou_based_cls_loss.device)
iou_based_reg_loss_full[pos_inds] = iou_based_reg_loss.view(-1, n_loss_per_box).mean(1)
combined_loss = iou_based_cls_loss.sum(dim=1) + iou_based_reg_loss_full
assert not torch.isnan(combined_loss).any()
# compute labels and targets using PAA
labels, reg_targets = self.compute_paa(
targets,
anchors,
iou_based_labels_flatten.view(N, -1),
combined_loss.view(N, -1),
matched_idx_all)
num_gpus = get_num_gpus()
labels_flatten = torch.cat(labels, dim=0).int()
reg_targets_flatten = torch.cat(reg_targets, dim=0)
pos_inds = torch.nonzero(labels_flatten > 0).squeeze(1)
total_num_pos = reduce_sum(pos_inds.new_tensor([pos_inds.numel()])).item()
num_pos_avg_per_gpu = max(total_num_pos / float(num_gpus), 1.0)
box_regression_flatten = box_regression_flatten[pos_inds]
reg_targets_flatten = reg_targets_flatten[pos_inds]
anchors_flatten = anchors_flatten[pos_inds]
if iou_pred is not None:
# compute iou prediction targets
iou_pred_flatten = iou_pred_flatten[pos_inds]
gt_boxes = self.box_coder.decode(reg_targets_flatten, anchors_flatten)
boxes = self.box_coder.decode(box_regression_flatten, anchors_flatten).detach()
ious = self.compute_ious(gt_boxes, boxes)
# compute iou losses
iou_pred_loss = self.iou_pred_loss_func(
iou_pred_flatten, ious) / num_pos_avg_per_gpu * self.iou_loss_weight
sum_ious_targets_avg_per_gpu = reduce_sum(ious.sum()).item() / float(num_gpus)
# set regression loss weights to ious between predicted boxes and GTs
reg_loss_weight = ious
else:
reg_loss_weight = None
reg_loss = self.compute_reg_loss(reg_targets_flatten,
box_regression_flatten,
anchors_flatten,
labels_flatten[pos_inds],
locations,
n_anchors,
weights=reg_loss_weight,
N=N)
cls_loss = self.cls_loss_func(box_cls_flatten, labels_flatten.int(), sum=False)
else:
reg_loss = box_regression_flatten.sum()
reg_norm = sum_ious_targets_avg_per_gpu if iou_pred is not None else num_pos_avg_per_gpu
res = [cls_loss.sum() / num_pos_avg_per_gpu,
reg_loss.sum() / reg_norm * self.cfg.MODEL.PAA.REG_LOSS_WEIGHT]
if iou_pred is not None:
res.append(iou_pred_loss)
return res
def compute_paa(self, targets, anchors, labels_all, loss_all, matched_idx_all):
"""
Args:
targets (batch_size): list of BoxLists for GT bboxes
anchors (batch_size, feature_lvls): anchor boxes per feature level
labels_all (batch_size x num_anchors): assigned labels
loss_all (batch_size x numa_nchors): calculated loss
matched_idx_all (batch_size x numa_nchors): best-matched GG bbox indexes
"""
device = loss_all.device
cls_labels = []
reg_targets = []
for im_i in range(len(targets)):
targets_per_im = targets[im_i]
assert targets_per_im.mode == "xyxy"
bboxes_per_im = targets_per_im.bbox
labels_per_im = targets_per_im.get_field("labels")
anchors_per_im = cat_boxlist(anchors[im_i])
labels_all_per_im = labels_all[im_i]
loss_all_per_im = loss_all[im_i]
matched_idx_all_per_im = matched_idx_all[im_i]
assert labels_all_per_im.shape == matched_idx_all_per_im.shape
num_anchors_per_level = [len(anchors_per_level.bbox)
for anchors_per_level in anchors[im_i]]
# select candidates based on IoUs between anchors and GTs
candidate_idxs = []
num_gt = bboxes_per_im.shape[0]
for gt in range(num_gt):
candidate_idxs_per_gt = []
star_idx = 0
for level, anchors_per_level in enumerate(anchors[im_i]):
end_idx = star_idx + num_anchors_per_level[level]
loss_per_level = loss_all_per_im[star_idx:end_idx]
labels_per_level = labels_all_per_im[star_idx:end_idx]
matched_idx_per_level = matched_idx_all_per_im[star_idx:end_idx]
match_idx = ((matched_idx_per_level == gt) &(labels_per_level > 0)).nonzero()[:, 0]
if match_idx.numel() > 0:
_, topk_idxs = loss_per_level[match_idx].topk(
min(match_idx.numel(), self.cfg.MODEL.PAA.TOPK), largest=False)
topk_idxs_per_level_per_gt = match_idx[topk_idxs]
candidate_idxs_per_gt.append(topk_idxs_per_level_per_gt + star_idx)
star_idx = end_idx
if candidate_idxs_per_gt:
candidate_idxs.append(torch.cat(candidate_idxs_per_gt))
else:
candidate_idxs.append(None)
# fit 2-mode GMM per GT box
n_labels = anchors_per_im.bbox.shape[0]
cls_labels_per_im = torch.zeros(n_labels, dtype=torch.long).to(device)
matched_gts = torch.zeros_like(anchors_per_im.bbox)
fg_inds = matched_idx_all_per_im >= 0
matched_gts[fg_inds] = bboxes_per_im[matched_idx_all_per_im[fg_inds]]
is_grey = None
for gt in range(num_gt):
if candidate_idxs[gt] is not None:
if candidate_idxs[gt].numel() > 1:
candidate_loss = loss_all_per_im[candidate_idxs[gt]]
candidate_loss, inds = candidate_loss.sort()
candidate_loss = candidate_loss.view(-1, 1).cpu().numpy()
min_loss, max_loss = candidate_loss.min(), candidate_loss.max()
means_init=[[min_loss], [max_loss]]
weights_init = [0.5, 0.5]
precisions_init=[[[1.0]], [[1.0]]]
gmm = skm.GaussianMixture(2,
weights_init=weights_init,
means_init=means_init,
precisions_init=precisions_init)
gmm.fit(candidate_loss)
components = gmm.predict(candidate_loss)
scores = gmm.score_samples(candidate_loss)
components = torch.from_numpy(components).to(device)
scores = torch.from_numpy(scores).to(device)
fgs = components == 0
bgs = components == 1
if fgs.nonzero().numel() > 0:
fg_max_score = scores[fgs].max().item()
fg_max_idx = (fgs & (scores == fg_max_score)).nonzero().min()
is_pos = inds[:fg_max_idx+1]
# half half (Fig 2. (a))
# probs = gmm.predict_proba(candidate_loss)
# pos_high = probs[:, 0] >= probs[:, 1]
# is_pos = inds[pos_high]
# half half end
# ignore middle (Fig 2. (b))
if bgs.nonzero().numel() > 0:
is_grey = inds[fgs | bgs]
bg_max_score = scores[bgs].max().item()
bg_max_idx = (bgs & (scores == bg_max_score)).nonzero().min()
is_neg = inds[-bg_max_idx-1:]
else:
is_neg = is_grey = None
# ignore middle end
# ignore middlehalf (Fig 2. (d))
# probs = gmm.predict_proba(candidate_loss)
# pos_high = probs[:, 0] >= probs[:, 1]
# is_grey = inds[pos_high]
# if bgs.nonzero().numel() > 0:
# pos_neg = probs[:, 0] < probs[:, 1]
# is_neg = inds[pos_neg]
# else:
# is_neg = None
# ignore middlehalf end
else:
# just treat all samples as positive for high recall.
is_pos = inds
is_neg = is_grey = None
else:
is_pos = 0
is_neg = None
is_grey = None
if is_grey is not None:
grey_idx = candidate_idxs[gt][is_grey]
cls_labels_per_im[grey_idx] = -1
if is_neg is not None:
neg_idx = candidate_idxs[gt][is_neg]
cls_labels_per_im[neg_idx] = 0
pos_idx = candidate_idxs[gt][is_pos]
cls_labels_per_im[pos_idx] = labels_per_im[gt].view(-1, 1)
matched_gts[pos_idx] = bboxes_per_im[gt].view(-1, 4)
reg_targets_per_im = self.box_coder.encode(matched_gts, anchors_per_im.bbox)
cls_labels.append(cls_labels_per_im)
reg_targets.append(reg_targets_per_im)
return cls_labels, reg_targets
def prepare_targets(self, targets, anchors):
cls_labels = []
reg_targets = []
for im_i in range(len(targets)):
targets_per_im = targets[im_i]
assert targets_per_im.mode == "xyxy"
bboxes_per_im = targets_per_im.bbox
labels_per_im = targets_per_im.get_field("labels")
anchors_per_im = cat_boxlist(anchors[im_i])
num_gt = bboxes_per_im.shape[0]
if self.cfg.MODEL.ATSS.POSITIVE_TYPE == 'SSC':
object_sizes_of_interest = [[-1, 64], [64, 128], [128, 256], [256, 512], [512, INF]]
area_per_im = targets_per_im.area()
expanded_object_sizes_of_interest = []
points = []
for l, anchors_per_level in enumerate(anchors[im_i]):
anchors_per_level = anchors_per_level.bbox
anchors_cx_per_level = (anchors_per_level[:, 2] + anchors_per_level[:, 0]) / 2.0
anchors_cy_per_level = (anchors_per_level[:, 3] + anchors_per_level[:, 1]) / 2.0
points_per_level = torch.stack((anchors_cx_per_level, anchors_cy_per_level), dim=1)
points.append(points_per_level)
object_sizes_of_interest_per_level = \
points_per_level.new_tensor(object_sizes_of_interest[l])
expanded_object_sizes_of_interest.append(
object_sizes_of_interest_per_level[None].expand(len(points_per_level), -1)
)
expanded_object_sizes_of_interest = torch.cat(expanded_object_sizes_of_interest, dim=0)
points = torch.cat(points, dim=0)
xs, ys = points[:, 0], points[:, 1]
l = xs[:, None] - bboxes_per_im[:, 0][None]
t = ys[:, None] - bboxes_per_im[:, 1][None]
r = bboxes_per_im[:, 2][None] - xs[:, None]
b = bboxes_per_im[:, 3][None] - ys[:, None]
reg_targets_per_im = torch.stack([l, t, r, b], dim=2)
is_in_boxes = reg_targets_per_im.min(dim=2)[0] > 0.01
max_reg_targets_per_im = reg_targets_per_im.max(dim=2)[0]
is_cared_in_the_level = \
(max_reg_targets_per_im >= expanded_object_sizes_of_interest[:, [0]]) & \
(max_reg_targets_per_im <= expanded_object_sizes_of_interest[:, [1]])
locations_to_gt_area = area_per_im[None].repeat(len(points), 1)
locations_to_gt_area[is_in_boxes == 0] = INF
locations_to_gt_area[is_cared_in_the_level == 0] = INF
locations_to_min_area, locations_to_gt_inds = locations_to_gt_area.min(dim=1)
cls_labels_per_im = labels_per_im[locations_to_gt_inds]
cls_labels_per_im[locations_to_min_area == INF] = 0
matched_gts = bboxes_per_im[locations_to_gt_inds]
elif self.cfg.MODEL.ATSS.POSITIVE_TYPE == 'ATSS':
num_anchors_per_level = [len(anchors_per_level.bbox) for anchors_per_level in anchors[im_i]]
ious = boxlist_iou(anchors_per_im, targets_per_im)
gt_cx = (bboxes_per_im[:, 2] + bboxes_per_im[:, 0]) / 2.0
gt_cy = (bboxes_per_im[:, 3] + bboxes_per_im[:, 1]) / 2.0
gt_points = torch.stack((gt_cx, gt_cy), dim=1)
anchors_cx_per_im = (anchors_per_im.bbox[:, 2] + anchors_per_im.bbox[:, 0]) / 2.0
anchors_cy_per_im = (anchors_per_im.bbox[:, 3] + anchors_per_im.bbox[:, 1]) / 2.0
anchor_points = torch.stack((anchors_cx_per_im, anchors_cy_per_im), dim=1)
distances = (anchor_points[:, None, :] - gt_points[None, :, :]).pow(2).sum(-1).sqrt()
# Selecting candidates based on the center distance between anchor box and object
candidate_idxs = []
star_idx = 0
for level, anchors_per_level in enumerate(anchors[im_i]):
end_idx = star_idx + num_anchors_per_level[level]
distances_per_level = distances[star_idx:end_idx, :]
_, topk_idxs_per_level = distances_per_level.topk(self.cfg.MODEL.ATSS.TOPK, dim=0, largest=False)
candidate_idxs.append(topk_idxs_per_level + star_idx)
star_idx = end_idx
candidate_idxs = torch.cat(candidate_idxs, dim=0)
# Using the sum of mean and standard deviation as the IoU threshold to select final positive samples
candidate_ious = ious[candidate_idxs, torch.arange(num_gt)]
iou_mean_per_gt = candidate_ious.mean(0)
iou_std_per_gt = candidate_ious.std(0)
iou_thresh_per_gt = iou_mean_per_gt + iou_std_per_gt
is_pos = candidate_ious >= iou_thresh_per_gt[None, :]
# Limiting the final positive samples’ center to object
anchor_num = anchors_cx_per_im.shape[0]
for ng in range(num_gt):
candidate_idxs[:, ng] += ng * anchor_num
e_anchors_cx = anchors_cx_per_im.view(1, -1).expand(num_gt, anchor_num).contiguous().view(-1)
e_anchors_cy = anchors_cy_per_im.view(1, -1).expand(num_gt, anchor_num).contiguous().view(-1)
candidate_idxs = candidate_idxs.view(-1)
l = e_anchors_cx[candidate_idxs].view(-1, num_gt) - bboxes_per_im[:, 0]
t = e_anchors_cy[candidate_idxs].view(-1, num_gt) - bboxes_per_im[:, 1]
r = bboxes_per_im[:, 2] - e_anchors_cx[candidate_idxs].view(-1, num_gt)
b = bboxes_per_im[:, 3] - e_anchors_cy[candidate_idxs].view(-1, num_gt)
is_in_gts = torch.stack([l, t, r, b], dim=1).min(dim=1)[0] > 0.01
is_pos = is_pos & is_in_gts
# if an anchor box is assigned to multiple gts, the one with the highest IoU will be selected.
ious_inf = torch.full_like(ious, -INF).t().contiguous().view(-1)
index = candidate_idxs.view(-1)[is_pos.view(-1)]
ious_inf[index] = ious.t().contiguous().view(-1)[index]
ious_inf = ious_inf.view(num_gt, -1).t()
anchors_to_gt_values, anchors_to_gt_indexs = ious_inf.max(dim=1)
cls_labels_per_im = labels_per_im[anchors_to_gt_indexs]
cls_labels_per_im[anchors_to_gt_values == -INF] = 0
matched_gts = bboxes_per_im[anchors_to_gt_indexs]
elif self.cfg.MODEL.ATSS.POSITIVE_TYPE == 'IoU':
match_quality_matrix = boxlist_iou(targets_per_im, anchors_per_im)
matched_idxs = self.matcher(match_quality_matrix)
targets_per_im = targets_per_im.copy_with_fields(['labels'])
matched_targets = targets_per_im[matched_idxs.clamp(min=0)]
cls_labels_per_im = matched_targets.get_field("labels")
cls_labels_per_im = cls_labels_per_im.to(dtype=torch.float32)
# Background (negative examples)
bg_indices = matched_idxs == Matcher.BELOW_LOW_THRESHOLD
cls_labels_per_im[bg_indices] = 0
# discard indices that are between thresholds
inds_to_discard = matched_idxs == Matcher.BETWEEN_THRESHOLDS
cls_labels_per_im[inds_to_discard] = -1
matched_gts = matched_targets.bbox
# Limiting positive samples’ center to object
# in order to filter out poor positives and use the centerness branch
pos_idxs = torch.nonzero(cls_labels_per_im > 0).squeeze(1)
pos_anchors_cx = (anchors_per_im.bbox[pos_idxs, 2] + anchors_per_im.bbox[pos_idxs, 0]) / 2.0
pos_anchors_cy = (anchors_per_im.bbox[pos_idxs, 3] + anchors_per_im.bbox[pos_idxs, 1]) / 2.0
l = pos_anchors_cx - matched_gts[pos_idxs, 0]
t = pos_anchors_cy - matched_gts[pos_idxs, 1]
r = matched_gts[pos_idxs, 2] - pos_anchors_cx
b = matched_gts[pos_idxs, 3] - pos_anchors_cy
is_in_gts = torch.stack([l, t, r, b], dim=1).min(dim=1)[0] > 0.01
cls_labels_per_im[pos_idxs[is_in_gts == 0]] = -1
else:
raise NotImplementedError
reg_targets_per_im = self.box_coder.encode(matched_gts, anchors_per_im.bbox)
cls_labels.append(cls_labels_per_im)
reg_targets.append(reg_targets_per_im)
return cls_labels, reg_targets
