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#!/usr/bin/env python3
# -*- coding:utf-8 -*-
# The code is based on
# https://github.com/Megvii-BaseDetection/YOLOX/blob/main/yolox/models/yolo_head.py
# Copyright (c) Megvii, Inc. and its affiliates.
import torch
import torch.nn as nn
import numpy as np
import torch.nn.functional as F
from yolov6.utils.figure_iou import IOUloss, pairwise_bbox_iou
class ComputeLoss:
'''Loss computation func.
This func contains SimOTA and siou loss.
'''
def __init__(self,
reg_weight=5.0,
iou_weight=3.0,
cls_weight=1.0,
center_radius=2.5,
eps=1e-7,
in_channels=[256, 512, 1024],
strides=[8, 16, 32],
n_anchors=1,
iou_type='ciou'
):
self.reg_weight = reg_weight
self.iou_weight = iou_weight
self.cls_weight = cls_weight
self.center_radius = center_radius
self.eps = eps
self.n_anchors = n_anchors
self.strides = strides
self.grids = [torch.zeros(1)] * len(in_channels)
# Define criteria
self.l1_loss = nn.L1Loss(reduction="none")
self.bcewithlog_loss = nn.BCEWithLogitsLoss(reduction="none")
self.iou_loss = IOUloss(iou_type=iou_type, reduction="none")
def __call__(
self,
outputs,
targets
):
dtype = outputs[0].type()
device = targets.device
loss_cls, loss_obj, loss_iou, loss_l1 = torch.zeros(1, device=device), torch.zeros(1, device=device), \
torch.zeros(1, device=device), torch.zeros(1, device=device)
num_classes = outputs[0].shape[-1] - 5
outputs, outputs_origin, gt_bboxes_scale, xy_shifts, expanded_strides = self.get_outputs_and_grids(
outputs, self.strides, dtype, device)
total_num_anchors = outputs.shape[1]
bbox_preds = outputs[:, :, :4] # [batch, n_anchors_all, 4]
bbox_preds_org = outputs_origin[:, :, :4] # [batch, n_anchors_all, 4]
obj_preds = outputs[:, :, 4].unsqueeze(-1) # [batch, n_anchors_all, 1]
cls_preds = outputs[:, :, 5:] # [batch, n_anchors_all, n_cls]
# targets
batch_size = bbox_preds.shape[0]
targets_list = np.zeros((batch_size, 1, 5)).tolist()
for i, item in enumerate(targets.cpu().numpy().tolist()):
targets_list[int(item[0])].append(item[1:])
max_len = max((len(l) for l in targets_list))
targets = torch.from_numpy(np.array(list(map(lambda l:l + [[-1,0,0,0,0]]*(max_len - len(l)), targets_list)))[:,1:,:]).to(targets.device)
num_targets_list = (targets.sum(dim=2) > 0).sum(dim=1) # number of objects
num_fg, num_gts = 0, 0
cls_targets, reg_targets, l1_targets, obj_targets, fg_masks = [], [], [], [], []
for batch_idx in range(batch_size):
num_gt = int(num_targets_list[batch_idx])
num_gts += num_gt
if num_gt == 0:
cls_target = outputs.new_zeros((0, num_classes))
reg_target = outputs.new_zeros((0, 4))
l1_target = outputs.new_zeros((0, 4))
obj_target = outputs.new_zeros((total_num_anchors, 1))
fg_mask = outputs.new_zeros(total_num_anchors).bool()
else:
gt_bboxes_per_image = targets[batch_idx, :num_gt, 1:5].mul_(gt_bboxes_scale)
gt_classes = targets[batch_idx, :num_gt, 0]
bboxes_preds_per_image = bbox_preds[batch_idx]
cls_preds_per_image = cls_preds[batch_idx]
obj_preds_per_image = obj_preds[batch_idx]
try:
(
gt_matched_classes,
fg_mask,
pred_ious_this_matching,
matched_gt_inds,
num_fg_img,
) = self.get_assignments(
batch_idx,
num_gt,
total_num_anchors,
gt_bboxes_per_image,
gt_classes,
bboxes_preds_per_image,
cls_preds_per_image,
obj_preds_per_image,
expanded_strides,
xy_shifts,
num_classes
)
except RuntimeError:
print(
"OOM RuntimeError is raised due to the huge memory cost during label assignment. \
CPU mode is applied in this batch. If you want to avoid this issue, \
try to reduce the batch size or image size."
)
torch.cuda.empty_cache()
print("------------CPU Mode for This Batch-------------")
_gt_bboxes_per_image = gt_bboxes_per_image.cpu().float()
_gt_classes = gt_classes.cpu().float()
_bboxes_preds_per_image = bboxes_preds_per_image.cpu().float()
_cls_preds_per_image = cls_preds_per_image.cpu().float()
_obj_preds_per_image = obj_preds_per_image.cpu().float()
_expanded_strides = expanded_strides.cpu().float()
_xy_shifts = xy_shifts.cpu()
(
gt_matched_classes,
fg_mask,
pred_ious_this_matching,
matched_gt_inds,
num_fg_img,
) = self.get_assignments(
batch_idx,
num_gt,
total_num_anchors,
_gt_bboxes_per_image,
_gt_classes,
_bboxes_preds_per_image,
_cls_preds_per_image,
_obj_preds_per_image,
_expanded_strides,
_xy_shifts,
num_classes
)
gt_matched_classes = gt_matched_classes.cuda()
fg_mask = fg_mask.cuda()
pred_ious_this_matching = pred_ious_this_matching.cuda()
matched_gt_inds = matched_gt_inds.cuda()
torch.cuda.empty_cache()
num_fg += num_fg_img
if num_fg_img > 0:
cls_target = F.one_hot(
gt_matched_classes.to(torch.int64), num_classes
) * pred_ious_this_matching.unsqueeze(-1)
obj_target = fg_mask.unsqueeze(-1)
reg_target = gt_bboxes_per_image[matched_gt_inds]
l1_target = self.get_l1_target(
outputs.new_zeros((num_fg_img, 4)),
gt_bboxes_per_image[matched_gt_inds],
expanded_strides[0][fg_mask],
xy_shifts=xy_shifts[0][fg_mask],
)
cls_targets.append(cls_target)
reg_targets.append(reg_target)
obj_targets.append(obj_target)
l1_targets.append(l1_target)
fg_masks.append(fg_mask)
cls_targets = torch.cat(cls_targets, 0)
reg_targets = torch.cat(reg_targets, 0)
obj_targets = torch.cat(obj_targets, 0)
l1_targets = torch.cat(l1_targets, 0)
fg_masks = torch.cat(fg_masks, 0)
num_fg = max(num_fg, 1)
# loss
loss_iou += (self.iou_loss(bbox_preds.view(-1, 4)[fg_masks].T, reg_targets)).sum() / num_fg
loss_l1 += (self.l1_loss(bbox_preds_org.view(-1, 4)[fg_masks], l1_targets)).sum() / num_fg
loss_obj += (self.bcewithlog_loss(obj_preds.view(-1, 1), obj_targets*1.0)).sum() / num_fg
loss_cls += (self.bcewithlog_loss(cls_preds.view(-1, num_classes)[fg_masks], cls_targets)).sum() / num_fg
total_losses = self.reg_weight * loss_iou + loss_l1 + loss_obj + loss_cls
return total_losses, torch.cat((self.reg_weight * loss_iou, loss_l1, loss_obj, loss_cls)).detach()
def decode_output(self, output, k, stride, dtype, device):
grid = self.grids[k].to(device)
batch_size = output.shape[0]
hsize, wsize = output.shape[2:4]
if grid.shape[2:4] != output.shape[2:4]:
yv, xv = torch.meshgrid([torch.arange(hsize), torch.arange(wsize)])
grid = torch.stack((xv, yv), 2).view(1, 1, hsize, wsize, 2).type(dtype).to(device)
self.grids[k] = grid
output = output.reshape(batch_size, self.n_anchors * hsize * wsize, -1)
output_origin = output.clone()
grid = grid.view(1, -1, 2)
output[..., :2] = (output[..., :2] + grid) * stride
output[..., 2:4] = torch.exp(output[..., 2:4]) * stride
return output, output_origin, grid, hsize, wsize
def get_outputs_and_grids(self, outputs, strides, dtype, device):
xy_shifts = []
expanded_strides = []
outputs_new = []
outputs_origin = []
for k, output in enumerate(outputs):
output, output_origin, grid, feat_h, feat_w = self.decode_output(
output, k, strides[k], dtype, device)
xy_shift = grid
expanded_stride = torch.full((1, grid.shape[1], 1), strides[k], dtype=grid.dtype, device=grid.device)
xy_shifts.append(xy_shift)
expanded_strides.append(expanded_stride)
outputs_new.append(output)
outputs_origin.append(output_origin)
xy_shifts = torch.cat(xy_shifts, 1) # [1, n_anchors_all, 2]
expanded_strides = torch.cat(expanded_strides, 1) # [1, n_anchors_all, 1]
outputs_origin = torch.cat(outputs_origin, 1)
outputs = torch.cat(outputs_new, 1)
feat_h *= strides[-1]
feat_w *= strides[-1]
gt_bboxes_scale = torch.Tensor([[feat_w, feat_h, feat_w, feat_h]]).type_as(outputs)
return outputs, outputs_origin, gt_bboxes_scale, xy_shifts, expanded_strides
def get_l1_target(self, l1_target, gt, stride, xy_shifts, eps=1e-8):
l1_target[:, 0:2] = gt[:, 0:2] / stride - xy_shifts
l1_target[:, 2:4] = torch.log(gt[:, 2:4] / stride + eps)
return l1_target
@torch.no_grad()
def get_assignments(
self,
batch_idx,
num_gt,
total_num_anchors,
gt_bboxes_per_image,
gt_classes,
bboxes_preds_per_image,
cls_preds_per_image,
obj_preds_per_image,
expanded_strides,
xy_shifts,
num_classes
):
fg_mask, is_in_boxes_and_center = self.get_in_boxes_info(
gt_bboxes_per_image,
expanded_strides,
xy_shifts,
total_num_anchors,
num_gt,
)
bboxes_preds_per_image = bboxes_preds_per_image[fg_mask]
cls_preds_ = cls_preds_per_image[fg_mask]
obj_preds_ = obj_preds_per_image[fg_mask]
num_in_boxes_anchor = bboxes_preds_per_image.shape[0]
# cost
pair_wise_ious = pairwise_bbox_iou(gt_bboxes_per_image, bboxes_preds_per_image, box_format='xywh')
pair_wise_ious_loss = -torch.log(pair_wise_ious + 1e-8)
gt_cls_per_image = (
F.one_hot(gt_classes.to(torch.int64), num_classes)
.float()
.unsqueeze(1)
.repeat(1, num_in_boxes_anchor, 1)
)
with torch.cuda.amp.autocast(enabled=False):
cls_preds_ = (
cls_preds_.float().sigmoid_().unsqueeze(0).repeat(num_gt, 1, 1)
* obj_preds_.float().sigmoid_().unsqueeze(0).repeat(num_gt, 1, 1)
)
pair_wise_cls_loss = F.binary_cross_entropy(
cls_preds_.sqrt_(), gt_cls_per_image, reduction="none"
).sum(-1)
del cls_preds_, obj_preds_
cost = (
self.cls_weight * pair_wise_cls_loss
+ self.iou_weight * pair_wise_ious_loss
+ 100000.0 * (~is_in_boxes_and_center)
)
(
num_fg,
gt_matched_classes,
pred_ious_this_matching,
matched_gt_inds,
) = self.dynamic_k_matching(cost, pair_wise_ious, gt_classes, num_gt, fg_mask)
del pair_wise_cls_loss, cost, pair_wise_ious, pair_wise_ious_loss
return (
gt_matched_classes,
fg_mask,
pred_ious_this_matching,
matched_gt_inds,
num_fg,
)
def get_in_boxes_info(
self,
gt_bboxes_per_image,
expanded_strides,
xy_shifts,
total_num_anchors,
num_gt,
):
expanded_strides_per_image = expanded_strides[0]
xy_shifts_per_image = xy_shifts[0] * expanded_strides_per_image
xy_centers_per_image = (
(xy_shifts_per_image + 0.5 * expanded_strides_per_image)
.unsqueeze(0)
.repeat(num_gt, 1, 1)
) # [n_anchor, 2] -> [n_gt, n_anchor, 2]
gt_bboxes_per_image_lt = (
(gt_bboxes_per_image[:, 0:2] - 0.5 * gt_bboxes_per_image[:, 2:4])
.unsqueeze(1)
.repeat(1, total_num_anchors, 1)
)
gt_bboxes_per_image_rb = (
(gt_bboxes_per_image[:, 0:2] + 0.5 * gt_bboxes_per_image[:, 2:4])
.unsqueeze(1)
.repeat(1, total_num_anchors, 1)
) # [n_gt, 2] -> [n_gt, n_anchor, 2]
b_lt = xy_centers_per_image - gt_bboxes_per_image_lt
b_rb = gt_bboxes_per_image_rb - xy_centers_per_image
bbox_deltas = torch.cat([b_lt, b_rb], 2)
is_in_boxes = bbox_deltas.min(dim=-1).values > 0.0
is_in_boxes_all = is_in_boxes.sum(dim=0) > 0
# in fixed center
gt_bboxes_per_image_lt = (gt_bboxes_per_image[:, 0:2]).unsqueeze(1).repeat(
1, total_num_anchors, 1
) - self.center_radius * expanded_strides_per_image.unsqueeze(0)
gt_bboxes_per_image_rb = (gt_bboxes_per_image[:, 0:2]).unsqueeze(1).repeat(
1, total_num_anchors, 1
) + self.center_radius * expanded_strides_per_image.unsqueeze(0)
c_lt = xy_centers_per_image - gt_bboxes_per_image_lt
c_rb = gt_bboxes_per_image_rb - xy_centers_per_image
center_deltas = torch.cat([c_lt, c_rb], 2)
is_in_centers = center_deltas.min(dim=-1).values > 0.0
is_in_centers_all = is_in_centers.sum(dim=0) > 0
# in boxes and in centers
is_in_boxes_anchor = is_in_boxes_all | is_in_centers_all
is_in_boxes_and_center = (
is_in_boxes[:, is_in_boxes_anchor] & is_in_centers[:, is_in_boxes_anchor]
)
return is_in_boxes_anchor, is_in_boxes_and_center
def dynamic_k_matching(self, cost, pair_wise_ious, gt_classes, num_gt, fg_mask):
matching_matrix = torch.zeros_like(cost, dtype=torch.uint8)
ious_in_boxes_matrix = pair_wise_ious
n_candidate_k = min(10, ious_in_boxes_matrix.size(1))
topk_ious, _ = torch.topk(ious_in_boxes_matrix, n_candidate_k, dim=1)
dynamic_ks = torch.clamp(topk_ious.sum(1).int(), min=1)
dynamic_ks = dynamic_ks.tolist()
for gt_idx in range(num_gt):
_, pos_idx = torch.topk(
cost[gt_idx], k=dynamic_ks[gt_idx], largest=False
)
matching_matrix[gt_idx][pos_idx] = 1
del topk_ious, dynamic_ks, pos_idx
anchor_matching_gt = matching_matrix.sum(0)
if (anchor_matching_gt > 1).sum() > 0:
_, cost_argmin = torch.min(cost[:, anchor_matching_gt > 1], dim=0)
matching_matrix[:, anchor_matching_gt > 1] *= 0
matching_matrix[cost_argmin, anchor_matching_gt > 1] = 1
fg_mask_inboxes = matching_matrix.sum(0) > 0
num_fg = fg_mask_inboxes.sum().item()
fg_mask[fg_mask.clone()] = fg_mask_inboxes
matched_gt_inds = matching_matrix[:, fg_mask_inboxes].argmax(0)
gt_matched_classes = gt_classes[matched_gt_inds]
pred_ious_this_matching = (matching_matrix * pair_wise_ious).sum(0)[
fg_mask_inboxes
]
return num_fg, gt_matched_classes, pred_ious_this_matching, matched_gt_inds