def kmeans_anchors(self):
self.logger.info(
f'Start cluster {self.num_anchors} YOLO anchors with K-means...')
bboxes = self.get_zero_center_bbox_tensor()
cluster_center_idx = torch.randint(
0, bboxes.shape[0], (self.num_anchors, )).to(self.device)
assignments = torch.zeros((bboxes.shape[0], )).to(self.device)
cluster_centers = bboxes[cluster_center_idx]
if self.num_anchors == 1:
cluster_centers = self.kmeans_maximization(bboxes, assignments,
cluster_centers)
anchors = bbox_xyxy_to_cxcywh(cluster_centers)[:, 2:].cpu().numpy()
anchors = sorted(anchors, key=lambda x: x[0] * x[1])
return anchors
prog_bar = mmcv.ProgressBar(self.iters)
for i in range(self.iters):
converged, assignments = self.kmeans_expectation(
bboxes, assignments, cluster_centers)
if converged:
self.logger.info(f'K-means process has converged at iter {i}.')
break
cluster_centers = self.kmeans_maximization(bboxes, assignments,
cluster_centers)
prog_bar.update()
print('\n')
avg_iou = bbox_overlaps(bboxes,
cluster_centers).max(1)[0].mean().item()
anchors = bbox_xyxy_to_cxcywh(cluster_centers)[:, 2:].cpu().numpy()
anchors = sorted(anchors, key=lambda x: x[0] * x[1])
self.logger.info(f'Anchor cluster finish. Average IOU: {avg_iou}')
return anchors
def _get_target_single(self,
cls_score,
bbox_pred,
gt_bboxes,
gt_labels,
img_meta,
gt_bboxes_ignore=None):
""""Compute regression and classification targets for one image.
Outputs from a single decoder layer of a single feature level are used.
Args:
cls_score (Tensor): Box score logits from a single decoder layer
for one image. Shape [num_query, cls_out_channels].
bbox_pred (Tensor): Sigmoid outputs from a single decoder layer
for one image, with normalized coordinate (cx, cy, w, h) and
shape [num_query, 4].
gt_bboxes (Tensor): Ground truth bboxes for one image with
shape (num_gts, 4) in [tl_x, tl_y, br_x, br_y] format.
gt_labels (Tensor): Ground truth class indices for one image
with shape (num_gts, ).
img_meta (dict): Meta information for one image.
gt_bboxes_ignore (Tensor, optional): Bounding boxes
which can be ignored. Default None.
Returns:
tuple[Tensor]: a tuple containing the following for one image.
- labels (Tensor): Labels of each image.
- label_weights (Tensor]): Label weights of each image.
- bbox_targets (Tensor): BBox targets of each image.
- bbox_weights (Tensor): BBox weights of each image.
- pos_inds (Tensor): Sampled positive indices for each image.
- neg_inds (Tensor): Sampled negative indices for each image.
"""
num_bboxes = bbox_pred.size(0)
# assigner and sampler
assign_result = self.assigner.assign(bbox_pred, cls_score, gt_bboxes,
gt_labels, img_meta,
gt_bboxes_ignore)
sampling_result = self.sampler.sample(assign_result, bbox_pred,
gt_bboxes)
pos_inds = sampling_result.pos_inds
neg_inds = sampling_result.neg_inds
# label targets
labels = gt_bboxes.new_full((num_bboxes, ),
self.num_classes,
dtype=torch.long)
labels[pos_inds] = gt_labels[sampling_result.pos_assigned_gt_inds]
label_weights = gt_bboxes.new_ones(num_bboxes)
# bbox targets
bbox_targets = torch.zeros_like(bbox_pred)
bbox_weights = torch.zeros_like(bbox_pred)
bbox_weights[pos_inds] = 1.0
img_h, img_w, _ = img_meta['img_shape']
# DETR regress the relative position of boxes (cxcywh) in the image.
# Thus the learning target should be normalized by the image size, also
# the box format should be converted from defaultly x1y1x2y2 to cxcywh.
factor = bbox_pred.new_tensor([img_w, img_h, img_w,
img_h]).unsqueeze(0)
pos_gt_bboxes_normalized = sampling_result.pos_gt_bboxes / factor
pos_gt_bboxes_targets = bbox_xyxy_to_cxcywh(pos_gt_bboxes_normalized)
bbox_targets[pos_inds] = pos_gt_bboxes_targets
return (labels, label_weights, bbox_targets, bbox_weights, pos_inds,
neg_inds)
def forward_train(self,
x,
proposal_boxes,
proposal_features,
img_metas,
gt_bboxes,
gt_labels,
gt_bboxes_ignore=None,
imgs_whwh=None,
gt_masks=None):
"""Forward function in training stage.
Args:
x (list[Tensor]): list of multi-level img features.
proposals (Tensor): Decoded proposal bboxes, has shape
(batch_size, num_proposals, 4)
proposal_features (Tensor): Expanded proposal
features, has shape
(batch_size, num_proposals, proposal_feature_channel)
img_metas (list[dict]): list of image info dict where
each dict has: 'img_shape', 'scale_factor', 'flip',
and may also contain 'filename', 'ori_shape',
'pad_shape', and 'img_norm_cfg'. For details on the
values of these keys see
`mmdet/datasets/pipelines/formatting.py:Collect`.
gt_bboxes (list[Tensor]): Ground truth bboxes for each image with
shape (num_gts, 4) in [tl_x, tl_y, br_x, br_y] format.
gt_labels (list[Tensor]): class indices corresponding to each box
gt_bboxes_ignore (None | list[Tensor]): specify which bounding
boxes can be ignored when computing the loss.
imgs_whwh (Tensor): Tensor with shape (batch_size, 4),
the dimension means
[img_width,img_height, img_width, img_height].
gt_masks (None | Tensor) : true segmentation masks for each box
used if the architecture supports a segmentation task.
Returns:
dict[str, Tensor]: a dictionary of loss components of all stage.
"""
num_imgs = len(img_metas)
num_proposals = proposal_boxes.size(1)
imgs_whwh = imgs_whwh.repeat(1, num_proposals, 1)
all_stage_bbox_results = []
proposal_list = [proposal_boxes[i] for i in range(len(proposal_boxes))]
object_feats = proposal_features
all_stage_loss = {}
for stage in range(self.num_stages):
rois = bbox2roi(proposal_list)
bbox_results = self._bbox_forward(stage, x, rois, object_feats,
img_metas)
all_stage_bbox_results.append(bbox_results)
if gt_bboxes_ignore is None:
# TODO support ignore
gt_bboxes_ignore = [None for _ in range(num_imgs)]
sampling_results = []
cls_pred_list = bbox_results['detach_cls_score_list']
proposal_list = bbox_results['detach_proposal_list']
for i in range(num_imgs):
normalize_bbox_ccwh = bbox_xyxy_to_cxcywh(proposal_list[i] /
imgs_whwh[i])
assign_result = self.bbox_assigner[stage].assign(
normalize_bbox_ccwh, cls_pred_list[i], gt_bboxes[i],
gt_labels[i], img_metas[i])
sampling_result = self.bbox_sampler[stage].sample(
assign_result, proposal_list[i], gt_bboxes[i])
sampling_results.append(sampling_result)
bbox_targets = self.bbox_head[stage].get_targets(
sampling_results, gt_bboxes, gt_labels, self.train_cfg[stage],
True)
cls_score = bbox_results['cls_score']
decode_bbox_pred = bbox_results['decode_bbox_pred']
single_stage_loss = self.bbox_head[stage].loss(
cls_score.view(-1, cls_score.size(-1)),
decode_bbox_pred.view(-1, 4),
*bbox_targets,
imgs_whwh=imgs_whwh)
for key, value in single_stage_loss.items():
all_stage_loss[f'stage{stage}_{key}'] = value * \
self.stage_loss_weights[stage]
object_feats = bbox_results['object_feats']
return all_stage_loss
def _get_l1_target(self, l1_target, gt_bboxes, priors, eps=1e-8):
"""Convert gt bboxes to center offset and log width height."""
gt_cxcywh = bbox_xyxy_to_cxcywh(gt_bboxes)
l1_target[:, :2] = (gt_cxcywh[:, :2] - priors[:, :2]) / priors[:, 2:]
l1_target[:, 2:] = torch.log(gt_cxcywh[:, 2:] / priors[:, 2:] + eps)
return l1_target
