text: # ------------------------------------------------------------------------
  # UP-DETR
  # Copyright (c) Tencent, Inc. and its affiliates. All Rights Reserved.
  # ------------------------------------------------------------------------
  # Modified from DETR (https://github.com/facebookresearch/detr)
  # Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved
  # ------------------------------------------------------------------------
  import argparse
  import datetime
  import json
  import random
  import time
  from pathlib import Path
  
  import numpy as np
  import torch
  from torch.utils.data import DataLoader, DistributedSampler
  
  import datasets
  import util.misc as utils
  from datasets import build_dataset, get_coco_api_from_dataset
  from engine import evaluate, train_one_epoch
  from models import build_model
  
  
  def get_args_parser():
      parser = argparse.ArgumentParser('Set transformer detector', add_help=False)
      parser.add_argument('--lr', default=1e-4, type=float)
      parser.add_argument('--lr_backbone', default=1e-5, type=float)
      parser.add_argument('--batch_size', default=2, type=int)
      parser.add_argument('--weight_decay', default=1e-4, type=float)
      parser.add_argument('--epochs', default=300, type=int)
      parser.add_argument('--lr_drop', default=200, type=int)
      parser.add_argument('--clip_max_norm', default=0.1, type=float,
                          help='gradient clipping max norm')
  
      # Model parameters
      parser.add_argument('--frozen_weights', type=str, default=None,
                          help="Path to the pretrained model. If set, only the mask head will be trained")
      # * Backbone
      parser.add_argument('--backbone', default='resnet50', type=str,
                          help="Name of the convolutional backbone to use")
      parser.add_argument('--dilation', action='store_true',
                          help="If true, we replace stride with dilation in the last convolutional block (DC5)")
      parser.add_argument('--position_embedding', default='sine', type=str, choices=('sine', 'learned'),
                          help="Type of positional embedding to use on top of the image features")
  
      # * Transformer
      parser.add_argument('--enc_layers', default=6, type=int,
                          help="Number of encoding layers in the transformer")
      parser.add_argument('--dec_layers', default=6, type=int,
                          help="Number of decoding layers in the transformer")
      parser.add_argument('--dim_feedforward', default=2048, type=int,
                          help="Intermediate size of the feedforward layers in the transformer blocks")
      parser.add_argument('--hidden_dim', default=256, type=int,
                          help="Size of the embeddings (dimension of the transformer)")
      parser.add_argument('--dropout', default=0.1, type=float,
                          help="Dropout applied in the transformer")
      parser.add_argument('--nheads', default=8, type=int,
                          help="Number of attention heads inside the transformer's attentions")
      parser.add_argument('--num_queries', default=100, type=int,
                          help="Number of query slots")
      parser.add_argument('--pre_norm', action='store_true')
  
      # * Segmentation
      parser.add_argument('--masks', action='store_true',
                          help="Train segmentation head if the flag is provided")
  
      # Loss
      parser.add_argument('--no_aux_loss', dest='aux_loss', action='store_false',
                          help="Disables auxiliary decoding losses (loss at each layer)")
      # * Matcher
      parser.add_argument('--set_cost_class', default=1, type=float,
                          help="Class coefficient in the matching cost")
      parser.add_argument('--set_cost_bbox', default=5, type=float,
                          help="L1 box coefficient in the matching cost")
      parser.add_argument('--set_cost_giou', default=2, type=float,
                          help="giou box coefficient in the matching cost")
      # * Loss coefficients
      parser.add_argument('--mask_loss_coef', default=1, type=float)
      parser.add_argument('--dice_loss_coef', default=1, type=float)
      parser.add_argument('--bbox_loss_coef', default=5, type=float)
      parser.add_argument('--giou_loss_coef', default=2, type=float)
      parser.add_argument('--eos_coef', default=0.1, type=float,
                          help="Relative classification weight of the no-object class")
  
      # dataset parameters
      parser.add_argument('--dataset_file', default='coco')
      parser.add_argument('--coco_path', type=str)
      parser.add_argument('--coco_panoptic_path', type=str)
      parser.add_argument('--remove_difficult', action='store_true')
  
      parser.add_argument('--output_dir', default='',
                          help='path where to save, empty for no saving')
      parser.add_argument('--device', default='cuda',
                          help='device to use for training / testing')
      parser.add_argument('--seed', default=42, type=int)
      parser.add_argument('--resume', default='', help='resume from checkpoint')
      parser.add_argument('--start_epoch', default=0, type=int, metavar='N',
                          help='start epoch')
      parser.add_argument('--eval', action='store_true')
      parser.add_argument('--num_workers', default=2, type=int)
  
      # distributed training parameters
      parser.add_argument('--world_size', default=1, type=int,
                          help='number of distributed processes')
      parser.add_argument('--dist_url', default='env://', help='url used to set up distributed training')
      parser.add_argument('--pretrain', default='', help='initialized from the pre-training model')
      return parser
  
  
  def main(args):
      utils.init_distributed_mode(args)
      print("git:\n  {}\n".format(utils.get_sha()))
  
      if args.frozen_weights is not None:
          assert args.masks, "Frozen training is meant for segmentation only"
      print(args)
  
      device = torch.device(args.device)
  
      # fix the seed for reproducibility
      seed = args.seed + utils.get_rank()
      torch.manual_seed(seed)
      np.random.seed(seed)
      random.seed(seed)
  
      model, criterion, postprocessors = build_model(args)
      model.to(device)
  
      model_without_ddp = model
      if args.distributed:
          model = torch.nn.parallel.DistributedDataParallel(model, device_ids=[args.gpu])
          model_without_ddp = model.module
      n_parameters = sum(p.numel() for p in model.parameters() if p.requires_grad)
      print('number of params:', n_parameters)
  
      param_dicts = [
          {"params": [p for n, p in model_without_ddp.named_parameters() if "backbone" not in n and p.requires_grad]},
          {
              "params": [p for n, p in model_without_ddp.named_parameters() if "backbone" in n and p.requires_grad],
              "lr": args.lr_backbone,
          },
      ]
      optimizer = torch.optim.AdamW(param_dicts, lr=args.lr,
                                    weight_decay=args.weight_decay)
      lr_scheduler = torch.optim.lr_scheduler.StepLR(optimizer, args.lr_drop)
  
      dataset_train = build_dataset(image_set='train', args=args)
      dataset_val = build_dataset(image_set='val', args=args)
  
      if args.distributed:
          sampler_train = DistributedSampler(dataset_train)
          sampler_val = DistributedSampler(dataset_val, shuffle=False)
      else:
          sampler_train = torch.utils.data.RandomSampler(dataset_train)
          sampler_val = torch.utils.data.SequentialSampler(dataset_val)
  
      batch_sampler_train = torch.utils.data.BatchSampler(
          sampler_train, args.batch_size, drop_last=True)
  
      data_loader_train = DataLoader(dataset_train, batch_sampler=batch_sampler_train,
                                     collate_fn=utils.collate_fn, num_workers=args.num_workers)
      data_loader_val = DataLoader(dataset_val, args.batch_size, sampler=sampler_val,
                                   drop_last=False, collate_fn=utils.collate_fn, num_workers=args.num_workers)
  
      if args.dataset_file == "coco_panoptic":
          # We also evaluate AP during panoptic training, on original coco DS
          coco_val = datasets.coco.build("val", args)
          base_ds = get_coco_api_from_dataset(coco_val)
      else:
          base_ds = get_coco_api_from_dataset(dataset_val)
  
      if args.frozen_weights is not None:
          checkpoint = torch.load(args.frozen_weights, map_location='cpu')
          model_without_ddp.detr.load_state_dict(checkpoint['model'])
  
      output_dir = Path(args.output_dir)
  
      if args.pretrain:
          print('Initialized from the pre-training model')
          checkpoint = torch.load(args.pretrain, map_location='cpu')
          state_dict = checkpoint['model']
          for k in list(state_dict.keys()):
              # remove useless class embed
              if 'class_embed' in k:
                  del state_dict[k]
          msg = model_without_ddp.load_state_dict(state_dict, strict=False)
          print(msg)
  
      if args.resume:
          if args.resume.startswith('https'):
              checkpoint = torch.hub.load_state_dict_from_url(
                  args.resume, map_location='cpu', check_hash=True)
          else:
              checkpoint = torch.load(args.resume, map_location='cpu')
          model_without_ddp.load_state_dict(checkpoint['model'])
          if not args.eval and 'optimizer' in checkpoint and 'lr_scheduler' in checkpoint and 'epoch' in checkpoint:
              optimizer.load_state_dict(checkpoint['optimizer'])
              lr_scheduler.load_state_dict(checkpoint['lr_scheduler'])
              args.start_epoch = checkpoint['epoch'] + 1
  
      if args.eval:
          test_stats, coco_evaluator = evaluate(model, criterion, postprocessors,
                                                data_loader_val, base_ds, device, args.output_dir)
          if args.output_dir:
              utils.save_on_master(coco_evaluator.coco_eval["bbox"].eval, output_dir / "eval.pth")
          return
  
      print("Start training")
      start_time = time.time()
      for epoch in range(args.start_epoch, args.epochs):
          if args.distributed:
              sampler_train.set_epoch(epoch)
          train_stats = train_one_epoch(
              model, criterion, data_loader_train, optimizer, device, epoch,
              args.clip_max_norm)
          lr_scheduler.step()
          if args.output_dir:
              checkpoint_paths = [output_dir / 'checkpoint.pth']
              # extra checkpoint before LR drop and every 100 epochs
              if (epoch + 1) % args.lr_drop == 0 or (epoch + 1) % 100 == 0:
                  checkpoint_paths.append(output_dir / f'checkpoint{epoch:04}.pth')
              for checkpoint_path in checkpoint_paths:
                  utils.save_on_master({
                      'model': model_without_ddp.state_dict(),
                      'optimizer': optimizer.state_dict(),
                      'lr_scheduler': lr_scheduler.state_dict(),
                      'epoch': epoch,
                      'args': args,
                  }, checkpoint_path)
  
          test_stats, coco_evaluator = evaluate(
              model, criterion, postprocessors, data_loader_val, base_ds, device, args.output_dir
          )
  
          log_stats = {**{f'train_{k}': v for k, v in train_stats.items()},
                       **{f'test_{k}': v for k, v in test_stats.items()},
                       'epoch': epoch,
                       'n_parameters': n_parameters}
  
          if args.output_dir and utils.is_main_process():
              with (output_dir / "log.txt").open("a") as f:
                  f.write(json.dumps(log_stats) + "\n")
  
              # for evaluation logs
              if coco_evaluator is not None:
                  (output_dir / 'eval').mkdir(exist_ok=True)
                  if "bbox" in coco_evaluator.coco_eval:
                      filenames = ['latest.pth']
                      if epoch % 50 == 0:
                          filenames.append(f'{epoch:03}.pth')
                      for name in filenames:
                          torch.save(coco_evaluator.coco_eval["bbox"].eval,
                                     output_dir / "eval" / name)
  
      total_time = time.time() - start_time
      total_time_str = str(datetime.timedelta(seconds=int(total_time)))
      print('Training time {}'.format(total_time_str))
  
  
  if __name__ == '__main__':
      parser = argparse.ArgumentParser('DETR training and evaluation script', parents=[get_args_parser()])
      args = parser.parse_args()
      if args.output_dir:
          Path(args.output_dir).mkdir(parents=True, exist_ok=True)
      main(args)
  