def visualize_training(self, batched_inputs, proposals):
"""
A function used to visualize images and proposals. It shows ground truth
bounding boxes on the original image and up to 20 top-scoring predicted
object proposals on the original image. Users can implement different
visualization functions for different models.
Args:
batched_inputs (list): a list that contains input to the model.
proposals (list): a list that contains predicted proposals. Both
batched_inputs and proposals should have the same length.
"""
storage = get_event_storage()
max_vis_prop = 20
for input, prop in zip(batched_inputs, proposals):
img = input["image"]
img = convert_image_to_rgb(img.permute(1, 2, 0), self.input_format)
v_gt = Visualizer(img, None)
v_gt = v_gt.overlay_instances(boxes=input["instances"].gt_boxes)
anno_img = v_gt.get_image()
box_size = min(len(prop.proposal_boxes), max_vis_prop)
v_pred = Visualizer(img, None)
v_pred = v_pred.overlay_instances(
boxes=prop.proposal_boxes[0:box_size].tensor.cpu().numpy())
prop_img = v_pred.get_image()
vis_img = np.concatenate((anno_img, prop_img), axis=1)
vis_img = vis_img.transpose(2, 0, 1)
vis_name = "Left: GT bounding boxes; Right: Predicted proposals"
storage.put_image(vis_name, vis_img)
break # only visualize one image in a batch
def _log_accuracy(self):
"""
Log the accuracy metrics to EventStorage.
"""
num_instances = self.gt_classes.numel()
pred_classes = self.pred_class_logits.argmax(dim=1)
bg_class_ind = self.pred_class_logits.shape[1] - 1
fg_inds = (self.gt_classes >= 0) & (self.gt_classes < bg_class_ind)
num_fg = fg_inds.nonzero().numel()
fg_gt_classes = self.gt_classes[fg_inds]
fg_pred_classes = pred_classes[fg_inds]
num_false_negative = (
fg_pred_classes == bg_class_ind).nonzero().numel()
num_accurate = (pred_classes == self.gt_classes).nonzero().numel()
fg_num_accurate = (fg_pred_classes == fg_gt_classes).nonzero().numel()
storage = get_event_storage()
storage.put_scalar("fast_rcnn/cls_accuracy",
num_accurate / num_instances)
if num_fg > 0:
storage.put_scalar("fast_rcnn/fg_cls_accuracy",
fg_num_accurate / num_fg)
storage.put_scalar("fast_rcnn/false_negative",
num_false_negative / num_fg)
def forward(self, batched_inputs):
"""
Args:
batched_inputs: a list, batched outputs of :class:`DatasetMapper` .
Each item in the list contains the inputs for one image.
For now, each item in the list is a dict that contains:
* image: Tensor, image in (C, H, W) format.
* instances (optional): groundtruth :class:`Instances`
* proposals (optional): :class:`Instances`, precomputed proposals.
Other information that's included in the original dicts, such as:
* "height", "width" (int): the output resolution of the model, used in inference.
See :meth:`postprocess` for details.
Returns:
list[dict]:
Each dict is the output for one input image.
The dict contains one key "instances" whose value is a :class:`Instances`.
The :class:`Instances` object has the following keys:
"pred_boxes", "pred_classes", "scores"
"""
if not self.training:
return self.inference(batched_inputs)
# backbone FPN
images = self.preprocess_image(batched_inputs)
features = self.backbone(images.tensor) # List of L, FPN features
# RPN
if "instances" in batched_inputs[0]:
gt_instances = [
x["instances"].to(self.device) for x in batched_inputs
] # List of N
else:
gt_instances = None
if self.proposal_generator:
proposals, proposal_losses = self.proposal_generator(
images, features, gt_instances)
# proposals is the output of find_top_rpn_proposals(), i.e., post_nms_top_K
else:
assert "proposals" in batched_inputs[0]
proposals = [
x["proposals"].to(self.device) for x in batched_inputs
]
proposal_losses = {}
# tensorboard visualize, visualize top-20 RPN proposals with largest objectness
if self.vis_period > 0:
storage = get_event_storage()
if storage.iter % self.vis_period == 0:
self.visualize_training(batched_inputs, proposals)
if self.moco and self.roi_heads.__class__ == 'MoCoROIHeadsV2':
self.roi_heads.gt_instances = gt_instances
# RoI
# ROI inputs are post_nms_top_k proposals.
# detector_losses includes Contrast Loss, 和业务层的 cls loss, and reg loss
_, detector_losses = self.roi_heads(images, features, proposals,
gt_instances)
losses = {}
losses.update(detector_losses)
losses.update(proposal_losses)
return losses
def losses(self):
"""
Return the losses from a set of RPN predictions and their associated ground-truth.
Returns:
dict[loss name -> loss value]: A dict mapping from loss name to loss value.
Loss names are: `loss_rpn_cls` for objectness classification and
`loss_rpn_loc` for proposal localization.
"""
def resample(label):
"""
Randomly sample a subset of positive and negative examples by overwriting
the label vector to the ignore value (-1) for all elements that are not
included in the sample.
"""
pos_idx, neg_idx = subsample_labels(label,
self.batch_size_per_image,
self.positive_fraction, 0)
# Fill with the ignore label (-1), then set positive and negative labels
label.fill_(-1)
label.scatter_(0, pos_idx, 1)
label.scatter_(0, neg_idx, 0)
return label
gt_objectness_logits, gt_anchor_deltas = self._get_ground_truth()
"""
gt_objectness_logits: list of N tensors. Tensor i is a vector whose length is the
total number of anchors in image i (i.e., len(anchors[i]))
gt_anchor_deltas: list of N tensors. Tensor i has shape (len(anchors[i]), B),
where B is the box dimension
"""
# Collect all objectness labels and delta targets over feature maps and images
# The final ordering is L, N, H, W, A from slowest to fastest axis.
num_anchors_per_map = [
np.prod(x.shape[1:]) for x in self.pred_objectness_logits
]
num_anchors_per_image = sum(num_anchors_per_map)
# Stack to: (N, num_anchors_per_image)
gt_objectness_logits = torch.stack(
[resample(label) for label in gt_objectness_logits], dim=0)
# Log the number of positive/negative anchors per-image that's used in training
num_pos_anchors = (gt_objectness_logits == 1).sum().item()
num_neg_anchors = (gt_objectness_logits == 0).sum().item()
storage = get_event_storage()
storage.put_scalar("rpn/num_pos_anchors",
num_pos_anchors / self.num_images)
storage.put_scalar("rpn/num_neg_anchors",
num_neg_anchors / self.num_images)
assert gt_objectness_logits.shape[1] == num_anchors_per_image
# Split to tuple of L tensors, each with shape (N, num_anchors_per_map)
gt_objectness_logits = torch.split(gt_objectness_logits,
num_anchors_per_map,
dim=1)
# Concat from all feature maps
gt_objectness_logits = cat([x.flatten() for x in gt_objectness_logits],
dim=0)
# Stack to: (N, num_anchors_per_image, B)
gt_anchor_deltas = torch.stack(gt_anchor_deltas, dim=0)
assert gt_anchor_deltas.shape[1] == num_anchors_per_image
B = gt_anchor_deltas.shape[2] # box dimension (4 or 5)
# Split to tuple of L tensors, each with shape (N, num_anchors_per_image)
gt_anchor_deltas = torch.split(gt_anchor_deltas,
num_anchors_per_map,
dim=1)
# Concat from all feature maps
gt_anchor_deltas = cat([x.reshape(-1, B) for x in gt_anchor_deltas],
dim=0)
# Collect all objectness logits and delta predictions over feature maps
# and images to arrive at the same shape as the labels and targets
# The final ordering is L, N, H, W, A from slowest to fastest axis.
pred_objectness_logits = cat(
[
# Reshape: (N, A, Hi, Wi) -> (N, Hi, Wi, A) -> (N*Hi*Wi*A, )
x.permute(0, 2, 3, 1).flatten()
for x in self.pred_objectness_logits
],
dim=0,
)
pred_anchor_deltas = cat(
[
# Reshape: (N, A*B, Hi, Wi) -> (N, A, B, Hi, Wi) -> (N, Hi, Wi, A, B)
# -> (N*Hi*Wi*A, B)
x.view(x.shape[0], -1, B, x.shape[-2], x.shape[-1]).permute(
0, 3, 4, 1, 2).reshape(-1, B)
for x in self.pred_anchor_deltas
],
dim=0,
)
objectness_loss, localization_loss = rpn_losses(
gt_objectness_logits,
gt_anchor_deltas,
pred_objectness_logits,
pred_anchor_deltas,
self.smooth_l1_beta,
)
normalizer = 1.0 / (self.batch_size_per_image * self.num_images)
loss_cls = objectness_loss * normalizer # cls: classification loss
loss_loc = localization_loss * normalizer # loc: localization loss
losses = {"loss_rpn_cls": loss_cls, "loss_rpn_loc": loss_loc}
return losses
def label_and_sample_proposals(self, proposals, targets):
"""
Prepare some proposals to be used to train the ROI heads.
It performs box matching between `proposals` and `targets`, and assigns
training labels to the proposals.
It returns `self.batch_size_per_image` random samples from proposals and groundtruth boxes,
with a fraction of positives that is no larger than `self.positive_sample_fraction.
Args:
See :meth:`ROIHeads.forward`
Returns:
list[Instances]:
length `N` list of `Instances`s containing the proposals
sampled for training. Each `Instances` has the following fields:
- proposal_boxes: the proposal boxes
- gt_boxes: the ground-truth box that the proposal is assigned to
(this is only meaningful if the proposal has a label > 0; if label = 0
then the ground-truth box is random)
Other fields such as "gt_classes" that's included in `targets`.
"""
gt_boxes = [x.gt_boxes for x in targets]
# Augment proposals with ground-truth boxes.
# In the case of learned proposals (e.g., RPN), when training starts
# the proposals will be low quality due to random initialization.
# It's possible that none of these initial
# proposals have high enough overlap with the gt objects to be used
# as positive examples for the second stage components (box head,
# cls head). Adding the gt boxes to the set of proposals
# ensures that the second stage components will have some positive
# examples from the start of training. For RPN, this augmentation improves
# convergence and empirically improves box AP on COCO by about 0.5
# points (under one tested configuration).
if self.proposal_append_gt:
proposals = add_ground_truth_to_proposals(gt_boxes, proposals)
proposals_with_gt = []
num_fg_samples = []
num_bg_samples = []
for proposals_per_image, targets_per_image in zip(proposals, targets):
has_gt = len(targets_per_image) > 0
match_quality_matrix = pairwise_iou(
targets_per_image.gt_boxes, proposals_per_image.proposal_boxes)
matched_idxs, matched_labels = self.proposal_matcher(
match_quality_matrix)
sampled_idxs, gt_classes = self._sample_proposals(
matched_idxs, matched_labels, targets_per_image.gt_classes)
# Set target attributes of the sampled proposals:
proposals_per_image = proposals_per_image[sampled_idxs]
proposals_per_image.gt_classes = gt_classes
# We index all the attributes of targets that start with "gt_"
# and have not been added to proposals yet (="gt_classes").
if has_gt:
sampled_targets = matched_idxs[sampled_idxs]
# NOTE: here the indexing waste some compute, because heads
# will filter the proposals again (by foreground/background,
# etc), so we essentially index the data twice.
for (trg_name,
trg_value) in targets_per_image.get_fields().items():
if trg_name.startswith(
"gt_") and not proposals_per_image.has(trg_name):
proposals_per_image.set(trg_name,
trg_value[sampled_targets])
else:
gt_boxes = Boxes(
targets_per_image.gt_boxes.tensor.new_zeros(
(len(sampled_idxs), 4)))
proposals_per_image.gt_boxes = gt_boxes
num_bg_samples.append(
(gt_classes == self.num_classes).sum().item())
num_fg_samples.append(gt_classes.numel() - num_bg_samples[-1])
proposals_with_gt.append(proposals_per_image)
# Log the number of fg/bg samples that are selected for training ROI heads
storage = get_event_storage()
storage.put_scalar("roi_head/num_fg_samples", np.mean(num_fg_samples))
storage.put_scalar("roi_head/num_bg_samples", np.mean(num_bg_samples))
return proposals_with_gt