RPNHead继承了AnchorHead(AnchorHead定义在mmdetection/mmdet/models/dense_heads/anchor_head.py文件里面),前面介绍的forward_single(),_get_bboxes_single(),loss()等函数都是重载的AnchorHead的方法.
anchor_head.py文件内容如下:
import numpy as np import torch import torch.nn as nn from mmcv.cnn import normal_init from mmcv.runner import force_fp32 from mmdet.core import (anchor_inside_flags, build_anchor_generator, build_assigner, build_bbox_coder, build_sampler, images_to_levels, multi_apply, multiclass_nms, unmap) from ..builder import HEADS, build_loss from .base_dense_head import BaseDenseHead from .dense_test_mixins import BBoxTestMixin @HEADS.register_module() class AnchorHead(BaseDenseHead, BBoxTestMixin): """Anchor-based head (RPN, RetinaNet, SSD, etc.). Args: num_classes (int): Number of categories excluding the background category. in_channels (int): Number of channels in the input feature map. feat_channels (int): Number of hidden channels. Used in child classes. anchor_generator (dict): Config dict for anchor generator bbox_coder (dict): Config of bounding box coder. reg_decoded_bbox (bool): If true, the regression loss would be applied on decoded bounding boxes. Default: False loss_cls (dict): Config of classification loss. loss_bbox (dict): Config of localization loss. train_cfg (dict): Training config of anchor head. test_cfg (dict): Testing config of anchor head. """ # noqa: W605 def __init__(self, num_classes, in_channels, feat_channels=256, anchor_generator=dict( type='AnchorGenerator', scales=[8, 16, 32], ratios=[0.5, 1.0, 2.0], strides=[4, 8, 16, 32, 64]), bbox_coder=dict( type='DeltaXYWHBBoxCoder', target_means=(.0, .0, .0, .0), target_stds=(1.0, 1.0, 1.0, 1.0)), reg_decoded_bbox=False, loss_cls=dict( type='CrossEntropyLoss', use_sigmoid=True, loss_weight=1.0), loss_bbox=dict( type='SmoothL1Loss', beta=1.0 / 9.0, loss_weight=1.0), train_cfg=None, test_cfg=None): super(AnchorHead, self).__init__() self.in_channels = in_channels self.num_classes = num_classes self.feat_channels = feat_channels self.use_sigmoid_cls = loss_cls.get('use_sigmoid', False) # TODO better way to determine whether sample or not self.sampling = loss_cls['type'] not in [ 'FocalLoss', 'GHMC', 'QualityFocalLoss' ] if self.use_sigmoid_cls: self.cls_out_channels = num_classes else: self.cls_out_channels = num_classes + 1 if self.cls_out_channels <= 0: raise ValueError(f'num_classes={num_classes} is too small') self.reg_decoded_bbox = reg_decoded_bbox self.bbox_coder = build_bbox_coder(bbox_coder) self.loss_cls = build_loss(loss_cls) self.loss_bbox = build_loss(loss_bbox) self.train_cfg = train_cfg self.test_cfg = test_cfg if self.train_cfg: self.assigner = build_assigner(self.train_cfg.assigner) # use PseudoSampler when sampling is False if self.sampling and hasattr(self.train_cfg, 'sampler'): sampler_cfg = self.train_cfg.sampler else: sampler_cfg = dict(type='PseudoSampler') self.sampler = build_sampler(sampler_cfg, context=self) self.fp16_enabled = False self.anchor_generator = build_anchor_generator(anchor_generator) # usually the numbers of anchors for each level are the same # except SSD detectors self.num_anchors = self.anchor_generator.num_base_anchors[0] self._init_layers() def _init_layers(self): """Initialize layers of the head.""" self.conv_cls = nn.Conv2d(self.in_channels, self.num_anchors * self.cls_out_channels, 1) self.conv_reg = nn.Conv2d(self.in_channels, self.num_anchors * 4, 1) def init_weights(self): """Initialize weights of the head.""" normal_init(self.conv_cls, std=0.01) normal_init(self.conv_reg, std=0.01) def forward_single(self, x): """Forward feature of a single scale level. Args: x (Tensor): Features of a single scale level. Returns: tuple: cls_score (Tensor): Cls scores for a single scale level the channels number is num_anchors * num_classes. bbox_pred (Tensor): Box energies / deltas for a single scale level, the channels number is num_anchors * 4. """ cls_score = self.conv_cls(x) bbox_pred = self.conv_reg(x) return cls_score, bbox_pred def forward(self, feats): """Forward features from the upstream network. Args: feats (tuple[Tensor]): Features from the upstream network, each is a 4D-tensor. Returns: tuple: A tuple of classification scores and bbox prediction. - cls_scores (list[Tensor]): Classification scores for all scale levels, each is a 4D-tensor, the channels number is num_anchors * num_classes. - bbox_preds (list[Tensor]): Box energies / deltas for all scale levels, each is a 4D-tensor, the channels number is num_anchors * 4. """ return multi_apply(self.forward_single, feats) def get_anchors(self, featmap_sizes, img_metas, device='cuda'): """Get anchors according to feature map sizes. Args: featmap_sizes (list[tuple]): Multi-level feature map sizes. img_metas (list[dict]): Image meta info. device (torch.device | str): Device for returned tensors Returns: tuple: anchor_list (list[Tensor]): Anchors of each image. valid_flag_list (list[Tensor]): Valid flags of each image. """ num_imgs = len(img_metas) # since feature map sizes of all images are the same, we only compute # anchors for one time multi_level_anchors = self.anchor_generator.grid_anchors( featmap_sizes, device) anchor_list = [multi_level_anchors for _ in range(num_imgs)] # for each image, we compute valid flags of multi level anchors valid_flag_list = [] for img_id, img_meta in enumerate(img_metas): multi_level_flags = self.anchor_generator.valid_flags( featmap_sizes, img_meta['pad_shape'], device) valid_flag_list.append(multi_level_flags) return anchor_list, valid_flag_list def _get_targets_single(self, flat_anchors, valid_flags, gt_bboxes, gt_bboxes_ignore, gt_labels, img_meta, label_channels=1, unmap_outputs=True): """Compute regression and classification targets for anchors in a single image. Args: flat_anchors (Tensor): Multi-level anchors of the image, which are concatenated into a single tensor of shape (num_anchors ,4) valid_flags (Tensor): Multi level valid flags of the image, which are concatenated into a single tensor of shape (num_anchors,). gt_bboxes (Tensor): Ground truth bboxes of the image, shape (num_gts, 4). img_meta (dict): Meta info of the image. gt_bboxes_ignore (Tensor): Ground truth bboxes to be ignored, shape (num_ignored_gts, 4). img_meta (dict): Meta info of the image. gt_labels (Tensor): Ground truth labels of each box, shape (num_gts,). label_channels (int): Channel of label. unmap_outputs (bool): Whether to map outputs back to the original set of anchors. Returns: tuple: labels_list (list[Tensor]): Labels of each level label_weights_list (list[Tensor]): Label weights of each level bbox_targets_list (list[Tensor]): BBox targets of each level bbox_weights_list (list[Tensor]): BBox weights of each level num_total_pos (int): Number of positive samples in all images num_total_neg (int): Number of negative samples in all images """ inside_flags = anchor_inside_flags(flat_anchors, valid_flags, img_meta['img_shape'][:2], self.train_cfg.allowed_border) if not inside_flags.any(): return (None, ) * 7 # assign gt and sample anchors anchors = flat_anchors[inside_flags, :] assign_result = self.assigner.assign( anchors, gt_bboxes, gt_bboxes_ignore, None if self.sampling else gt_labels) sampling_result = self.sampler.sample(assign_result, anchors, gt_bboxes) num_valid_anchors = anchors.shape[0] bbox_targets = torch.zeros_like(anchors) bbox_weights = torch.zeros_like(anchors) labels = anchors.new_full((num_valid_anchors, ), self.num_classes, dtype=torch.long) label_weights = anchors.new_zeros(num_valid_anchors, dtype=torch.float) pos_inds = sampling_result.pos_inds neg_inds = sampling_result.neg_inds if len(pos_inds) > 0: if not self.reg_decoded_bbox: pos_bbox_targets = self.bbox_coder.encode( sampling_result.pos_bboxes, sampling_result.pos_gt_bboxes) else: pos_bbox_targets = sampling_result.pos_gt_bboxes bbox_targets[pos_inds, :] = pos_bbox_targets bbox_weights[pos_inds, :] = 1.0 if gt_labels is None: # Only rpn gives gt_labels as None # Foreground is the first class since v2.5.0 labels[pos_inds] = 0 else: labels[pos_inds] = gt_labels[ sampling_result.pos_assigned_gt_inds] if self.train_cfg.pos_weight <= 0: label_weights[pos_inds] = 1.0 else: label_weights[pos_inds] = self.train_cfg.pos_weight if len(neg_inds) > 0: label_weights[neg_inds] = 1.0 # map up to original set of anchors if unmap_outputs: num_total_anchors = flat_anchors.size(0) labels = unmap( labels, num_total_anchors, inside_flags, fill=self.num_classes) # fill bg label label_weights = unmap(label_weights, num_total_anchors, inside_flags) bbox_targets = unmap(bbox_targets, num_total_anchors, inside_flags) bbox_weights = unmap(bbox_weights, num_total_anchors, inside_flags) return (labels, label_weights, bbox_targets, bbox_weights, pos_inds, neg_inds, sampling_result) def get_targets(self, anchor_list, valid_flag_list, gt_bboxes_list, img_metas, gt_bboxes_ignore_list=None, gt_labels_list=None, label_channels=1, unmap_outputs=True, return_sampling_results=False): """Compute regression and classification targets for anchors in multiple images. Args: anchor_list (list[list[Tensor]]): Multi level anchors of each image. The outer list indicates images, and the inner list corresponds to feature levels of the image. Each element of the inner list is a tensor of shape (num_anchors, 4). valid_flag_list (list[list[Tensor]]): Multi level valid flags of each image. The outer list indicates images, and the inner list corresponds to feature levels of the image. Each element of the inner list is a tensor of shape (num_anchors, ) gt_bboxes_list (list[Tensor]): Ground truth bboxes of each image. img_metas (list[dict]): Meta info of each image. gt_bboxes_ignore_list (list[Tensor]): Ground truth bboxes to be ignored. gt_labels_list (list[Tensor]): Ground truth labels of each box. label_channels (int): Channel of label. unmap_outputs (bool): Whether to map outputs back to the original set of anchors. Returns: tuple: Usually returns a tuple containing learning targets. - labels_list (list[Tensor]): Labels of each level. - label_weights_list (list[Tensor]): Label weights of each level. - bbox_targets_list (list[Tensor]): BBox targets of each level. - bbox_weights_list (list[Tensor]): BBox weights of each level. - num_total_pos (int): Number of positive samples in all images. - num_total_neg (int): Number of negative samples in all images. additional_returns: This function enables user-defined returns from `self._get_targets_single`. These returns are currently refined to properties at each feature map (i.e. having HxW dimension). The results will be concatenated after the end """ num_imgs = len(img_metas) assert len(anchor_list) == len(valid_flag_list) == num_imgs # anchor number of multi levels num_level_anchors = [anchors.size(0) for anchors in anchor_list[0]] # concat all level anchors to a single tensor concat_anchor_list = [] concat_valid_flag_list = [] for i in range(num_imgs): assert len(anchor_list[i]) == len(valid_flag_list[i]) concat_anchor_list.append(torch.cat(anchor_list[i])) concat_valid_flag_list.append(torch.cat(valid_flag_list[i])) # compute targets for each image if gt_bboxes_ignore_list is None: gt_bboxes_ignore_list = [None for _ in range(num_imgs)] if gt_labels_list is None: gt_labels_list = [None for _ in range(num_imgs)] results = multi_apply( self._get_targets_single, concat_anchor_list, concat_valid_flag_list, gt_bboxes_list, gt_bboxes_ignore_list, gt_labels_list, img_metas, label_channels=label_channels, unmap_outputs=unmap_outputs) (all_labels, all_label_weights, all_bbox_targets, all_bbox_weights, pos_inds_list, neg_inds_list, sampling_results_list) = results[:7] # t1 = all_labels[0].cpu().numpy() # t2 = all_label_weights[0].cpu().numpy() # t3 = all_bbox_targets[0].cpu().numpy() # t4 = all_bbox_weights[0].cpu().numpy() rest_results = list(results[7:]) # user-added return values # no valid anchors if any([labels is None for labels in all_labels]): return None # sampled anchors of all images num_total_pos = sum([max(inds.numel(), 1) for inds in pos_inds_list]) num_total_neg = sum([max(inds.numel(), 1) for inds in neg_inds_list]) # split targets to a list w.r.t. multiple levels labels_list = images_to_levels(all_labels, num_level_anchors) label_weights_list = images_to_levels(all_label_weights, num_level_anchors) bbox_targets_list = images_to_levels(all_bbox_targets, num_level_anchors) bbox_weights_list = images_to_levels(all_bbox_weights, num_level_anchors) res = (labels_list, label_weights_list, bbox_targets_list, bbox_weights_list, num_total_pos, num_total_neg) if return_sampling_results: res = res + (sampling_results_list, ) for i, r in enumerate(rest_results): # user-added return values rest_results[i] = images_to_levels(r, num_level_anchors) return res + tuple(rest_results) def loss_single(self, cls_score, bbox_pred, anchors, labels, label_weights, bbox_targets, bbox_weights, num_total_samples): """Compute loss of a single scale level. Args: cls_score (Tensor): Box scores for each scale level Has shape (N, num_anchors * num_classes, H, W). bbox_pred (Tensor): Box energies / deltas for each scale level with shape (N, num_anchors * 4, H, W). anchors (Tensor): Box reference for each scale level with shape (N, num_total_anchors, 4). labels (Tensor): Labels of each anchors with shape (N, num_total_anchors). label_weights (Tensor): Label weights of each anchor with shape (N, num_total_anchors) bbox_targets (Tensor): BBox regression targets of each anchor wight shape (N, num_total_anchors, 4). bbox_weights (Tensor): BBox regression loss weights of each anchor with shape (N, num_total_anchors, 4). num_total_samples (int): If sampling, num total samples equal to the number of total anchors; Otherwise, it is the number of positive anchors. Returns: dict[str, Tensor]: A dictionary of loss components. """ # classification loss labels = labels.reshape(-1) label_weights = label_weights.reshape(-1) # t1 = labels.cpu().numpy() # t2 = label_weights.cpu().numpy() cls_score = cls_score.permute(0, 2, 3, 1).reshape(-1, self.cls_out_channels) loss_cls = self.loss_cls( cls_score, labels, label_weights, avg_factor=num_total_samples) # regression loss bbox_targets = bbox_targets.reshape(-1, 4) bbox_weights = bbox_weights.reshape(-1, 4) bbox_pred = bbox_pred.permute(0, 2, 3, 1).reshape(-1, 4) if self.reg_decoded_bbox: anchors = anchors.reshape(-1, 4) bbox_pred = self.bbox_coder.decode(anchors, bbox_pred) loss_bbox = self.loss_bbox( bbox_pred, bbox_targets, bbox_weights, avg_factor=num_total_samples) return loss_cls, loss_bbox @force_fp32(apply_to=('cls_scores', 'bbox_preds')) 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]): 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 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. Default: None Returns: dict[str, Tensor]: A dictionary of loss components. """ featmap_sizes = [featmap.size()[-2:] for featmap in cls_scores] assert len(featmap_sizes) == self.anchor_generator.num_levels device = cls_scores[0].device anchor_list, valid_flag_list = self.get_anchors( featmap_sizes, img_metas, device=device) label_channels = self.cls_out_channels if self.use_sigmoid_cls else 1 cls_reg_targets = self.get_targets( anchor_list, valid_flag_list, gt_bboxes, img_metas, gt_bboxes_ignore_list=gt_bboxes_ignore, gt_labels_list=gt_labels, label_channels=label_channels) if cls_reg_targets is None: return None (labels_list, label_weights_list, bbox_targets_list, bbox_weights_list, num_total_pos, num_total_neg) = cls_reg_targets num_total_samples = ( num_total_pos + num_total_neg if self.sampling else num_total_pos) # anchor number of multi levels num_level_anchors = [anchors.size(0) for anchors in anchor_list[0]] # concat all level anchors and flags to a single tensor concat_anchor_list = [] for i in range(len(anchor_list)): concat_anchor_list.append(torch.cat(anchor_list[i])) all_anchor_list = images_to_levels(concat_anchor_list, num_level_anchors) losses_cls, losses_bbox = multi_apply( self.loss_single, cls_scores, bbox_preds, all_anchor_list, labels_list, label_weights_list, bbox_targets_list, bbox_weights_list, num_total_samples=num_total_samples) return dict(loss_cls=losses_cls, loss_bbox=losses_bbox) @force_fp32(apply_to=('cls_scores', 'bbox_preds')) def get_bboxes(self, cls_scores, bbox_preds, img_metas, cfg=None, rescale=False, with_nms=True): """Transform network output for a batch into bbox predictions. 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) img_metas (list[dict]): Meta information of each image, e.g., image size, scaling factor, etc. cfg (mmcv.Config | None): Test / postprocessing configuration, if None, test_cfg would be used rescale (bool): If True, return boxes in original image space. Default: False. with_nms (bool): If True, do nms before return boxes. Default: True. Returns: list[tuple[Tensor, Tensor]]: Each item in result_list is 2-tuple. The first item is an (n, 5) tensor, where the first 4 columns are bounding box positions (tl_x, tl_y, br_x, br_y) and the 5-th column is a score between 0 and 1. The second item is a (n,) tensor where each item is the predicted class labelof the corresponding box. Example: >>> import mmcv >>> self = AnchorHead( >>> num_classes=9, >>> in_channels=1, >>> anchor_generator=dict( >>> type='AnchorGenerator', >>> scales=[8], >>> ratios=[0.5, 1.0, 2.0], >>> strides=[4,])) >>> img_metas = [{'img_shape': (32, 32, 3), 'scale_factor': 1}] >>> cfg = mmcv.Config(dict( >>> score_thr=0.00, >>> nms=dict(type='nms', iou_thr=1.0), >>> max_per_img=10)) >>> feat = torch.rand(1, 1, 3, 3) >>> cls_score, bbox_pred = self.forward_single(feat) >>> # note the input lists are over different levels, not images >>> cls_scores, bbox_preds = [cls_score], [bbox_pred] >>> result_list = self.get_bboxes(cls_scores, bbox_preds, >>> img_metas, cfg) >>> det_bboxes, det_labels = result_list[0] >>> assert len(result_list) == 1 >>> assert det_bboxes.shape[1] == 5 >>> assert len(det_bboxes) == len(det_labels) == cfg.max_per_img """ assert len(cls_scores) == len(bbox_preds) num_levels = len(cls_scores) device = cls_scores[0].device featmap_sizes = [cls_scores[i].shape[-2:] for i in range(num_levels)] mlvl_anchors = self.anchor_generator.grid_anchors( featmap_sizes, device=device) result_list = [] for img_id in range(len(img_metas)): cls_score_list = [ cls_scores[i][img_id].detach() for i in range(num_levels) ] bbox_pred_list = [ bbox_preds[i][img_id].detach() for i in range(num_levels) ] img_shape = img_metas[img_id]['img_shape'] scale_factor = img_metas[img_id]['scale_factor'] if with_nms: # some heads don't support with_nms argument proposals = self._get_bboxes_single(cls_score_list, bbox_pred_list, mlvl_anchors, img_shape, scale_factor, cfg, rescale) else: proposals = self._get_bboxes_single(cls_score_list, bbox_pred_list, mlvl_anchors, img_shape, scale_factor, cfg, rescale, with_nms) result_list.append(proposals) return result_list def _get_bboxes_single(self, cls_score_list, bbox_pred_list, mlvl_anchors, img_shape, scale_factor, cfg, rescale=False, with_nms=True): """Transform outputs for a single batch item into bbox predictions. Args: cls_score_list (list[Tensor]): Box scores for a single scale level Has shape (num_anchors * num_classes, H, W). bbox_pred_list (list[Tensor]): Box energies / deltas for a single scale level with shape (num_anchors * 4, H, W). mlvl_anchors (list[Tensor]): Box reference for a single scale level with shape (num_total_anchors, 4). img_shape (tuple[int]): Shape of the input image, (height, width, 3). scale_factor (ndarray): Scale factor of the image arange as (w_scale, h_scale, w_scale, h_scale). cfg (mmcv.Config): Test / postprocessing configuration, if None, test_cfg would be used. rescale (bool): If True, return boxes in original image space. Default: False. with_nms (bool): If True, do nms before return boxes. Default: True. Returns: Tensor: Labeled boxes in shape (n, 5), where the first 4 columns are bounding box positions (tl_x, tl_y, br_x, br_y) and the 5-th column is a score between 0 and 1. """ cfg = self.test_cfg if cfg is None else cfg assert len(cls_score_list) == len(bbox_pred_list) == len(mlvl_anchors) mlvl_bboxes = [] mlvl_scores = [] for cls_score, bbox_pred, anchors in zip(cls_score_list, bbox_pred_list, mlvl_anchors): assert cls_score.size()[-2:] == bbox_pred.size()[-2:] cls_score = cls_score.permute(1, 2, 0).reshape(-1, self.cls_out_channels) if self.use_sigmoid_cls: scores = cls_score.sigmoid() else: scores = cls_score.softmax(-1) bbox_pred = bbox_pred.permute(1, 2, 0).reshape(-1, 4) nms_pre = cfg.get('nms_pre', -1) if nms_pre > 0 and scores.shape[0] > nms_pre: # Get maximum scores for foreground classes. if self.use_sigmoid_cls: max_scores, _ = scores.max(dim=1) else: # remind that we set FG labels to [0, num_class-1] # since mmdet v2.0 # BG cat_id: num_class max_scores, _ = scores[:, :-1].max(dim=1) _, topk_inds = max_scores.topk(nms_pre) anchors = anchors[topk_inds, :] bbox_pred = bbox_pred[topk_inds, :] scores = scores[topk_inds, :] bboxes = self.bbox_coder.decode( anchors, bbox_pred, max_shape=img_shape) mlvl_bboxes.append(bboxes) mlvl_scores.append(scores) mlvl_bboxes = torch.cat(mlvl_bboxes) if rescale: mlvl_bboxes /= mlvl_bboxes.new_tensor(scale_factor) mlvl_scores = torch.cat(mlvl_scores) if self.use_sigmoid_cls: # Add a dummy background class to the backend when using sigmoid # remind that we set FG labels to [0, num_class-1] since mmdet v2.0 # BG cat_id: num_class padding = mlvl_scores.new_zeros(mlvl_scores.shape[0], 1) mlvl_scores = torch.cat([mlvl_scores, padding], dim=1) t = mlvl_scores.detach().cpu().numpy() if with_nms: det_bboxes, det_labels = multiclass_nms(mlvl_bboxes, mlvl_scores, cfg.score_thr, cfg.nms, cfg.max_per_img) return det_bboxes, det_labels else: return mlvl_bboxes, mlvl_scores def aug_test(self, feats, img_metas, rescale=False): """Test function with test time augmentation. Args: feats (list[Tensor]): the outer list indicates test-time augmentations and inner Tensor should have a shape NxCxHxW, which contains features for all images in the batch. img_metas (list[list[dict]]): the outer list indicates test-time augs (multiscale, flip, etc.) and the inner list indicates images in a batch. each dict has image information. rescale (bool, optional): Whether to rescale the results. Defaults to False. Returns: list[ndarray]: bbox results of each class """ return self.aug_test_bboxes(feats, img_metas, rescale=rescale)
AnchorHead除了__init__(),_init_layers(),init_weights()等函数外,还包括以下函数:
(1)get_anchors(),根据特征图的尺寸获得Anchor;
(2)get_bboxes(),获得所有bboxes的预测值,通过调用_get_bboxes_single()函数来实现;
(3)_get_bboxes_single(),获得FPN一个层次的特征图bboxes的预测值;
(4)get_targets(),获得目标值,通过调用_get_targets_single()函数来实现;
(5)_get_targets_single(),获得FPN一个层次的特征图目标值;
(6)forward(),神经网络的前向传播,通过调用forward_single()来实现;
(7)forward_single(),FPN一个层次的特征图的前向传播;
(8)loss(),计算损失函数值,通过调用loss_single()来实现;
(9)loss_single(),计算FPN一个层次的特征图的损失函数值.
训练时,这些函数的执行/调用顺序如下所示:
forward()-->
forward_single()(RPNHead重载)-->
get_anchors()-->
get_targets()-->
_get_targets_single()-->
get_bboxes()-->
_get_bboxes_single()(RPNHead重载)
loss()-->
loss_single()-->