def main()

in finetune_video.py [0:0]


def main(args, writer):

    # Create Logger
    logger, training_stats = initialize_exp(
        args, "epoch", "loss", "prec1", "prec5", 
        "loss_val", "prec1_val", "prec5_val"
    )

    # Set CudNN benchmark
    torch.backends.cudnn.benchmark = True

    # Load model
    logger.info("Loading model")
    model = load_model(
        vid_base_arch=args.vid_base_arch, 
        aud_base_arch=args.aud_base_arch, 
        pretrained=args.pretrained,
        num_classes=args.num_clusters,
        norm_feat=False,
        use_mlp=args.use_mlp,
        headcount=args.headcount,
    )

    # Load model weights
    weight_path_type = type(args.weights_path)
    if weight_path_type == str:
        weight_path_not_none = args.weights_path != 'None' 
    else:
        weight_path_not_none = args.weights_path is not None
    if not args.pretrained and weight_path_not_none:
        logger.info("Loading model weights")
        if os.path.exists(args.weights_path):
            ckpt_dict = torch.load(args.weights_path)
            model_weights = ckpt_dict["model"]
            logger.info(f"Epoch checkpoint: {args.ckpt_epoch}")
            load_model_parameters(model, model_weights)
    logger.info(f"Loading model done")

    # Add FC layer to model for fine-tuning or feature extracting
    model = Finetune_Model(
        model.video_network.base, 
        get_video_dim(vid_base_arch=args.vid_base_arch), 
        NUM_CLASSES[args.dataset], 
        use_dropout=args.use_dropout, 
        use_bn=args.use_bn, 
        use_l2_norm=args.use_l2_norm, 
        dropout=0.7
    )

    # Create DataParallel model
    model = model.cuda()
    model = torch.nn.DataParallel(model)
    model_without_ddp = model.module

    # Get params for optimization
    params = []
    if args.feature_extract: # feature_extract only classifer
        for name, param in model_without_ddp.classifier.named_parameters():
            logger.info((name, param.shape))
            params.append(
                {'params': param, 
                'lr': args.head_lr, 
                'weight_decay': args.weight_decay
            })
    else: # finetune
        for name, param in model_without_ddp.classifier.named_parameters():
            logger.info((name, param.shape))
            params.append(
                {'params': param, 
                'lr': args.head_lr, 
                'weight_decay': args.weight_decay
            })
        for name, param in model_without_ddp.base.named_parameters():
            logger.info((name, param.shape))
            params.append(
                {'params': param, 
                'lr': args.base_lr, 
                'weight_decay': args.wd_base
            })

    logger.info("Creating AV Datasets")
    dataset = AVideoDataset(
        ds_name=args.dataset,
        root_dir=args.root_dir,
        mode='train',
        num_frames=args.clip_len,
        sample_rate=args.steps_bet_clips,
        num_train_clips=args.train_clips_per_video,
        train_crop_size=128 if args.augtype == 1 else 224,
        seed=None,
        fold=args.fold,
        colorjitter=args.colorjitter,
        temp_jitter=True,
        center_crop=False,
        target_fps=30,
        decode_audio=False,
    )
    dataset_test = AVideoDataset(
        ds_name=args.dataset,
        root_dir=args.root_dir,
        mode='test',
        num_frames=args.clip_len,
        sample_rate=args.steps_bet_clips,
        test_crop_size=128 if args.augtype == 1 else 224,
        num_spatial_crops=args.num_spatial_crops,
        num_ensemble_views=args.val_clips_per_video,
        seed=None,
        fold=args.fold,
        colorjitter=args.test_time_cj,
        temp_jitter=True,
        target_fps=30,
        decode_audio=False,
    )

    # Creating dataloaders
    logger.info("Creating data loaders")
    data_loader = torch.utils.data.DataLoader(
        dataset, 
        batch_size=args.batch_size,
        sampler=None,
        num_workers=args.workers,
        pin_memory=True, 
        drop_last=True,
        shuffle=True
    )
    data_loader_test = torch.utils.data.DataLoader(
        dataset_test, 
        batch_size=args.batch_size,
        sampler=None,
        num_workers=args.workers,
        pin_memory=True, 
        drop_last=False
    )

    # linearly scale LR and set up optimizer
    if args.optim_name == 'sgd':
        optimizer = torch.optim.SGD(
            params,
            lr=args.head_lr, 
            momentum=args.momentum, 
            weight_decay=args.weight_decay
        )
    elif args.optim_name == 'adam':
        optimizer = torch.optim.Adam(
            params,
            lr=args.head_lr, 
            weight_decay=args.weight_decay
        )

    # Multi-step LR scheduler
    if args.use_scheduler:
        lr_milestones = args.lr_milestones.split(',')
        milestones = [int(lr) - args.lr_warmup_epochs for lr in lr_milestones]
        if args.lr_warmup_epochs > 0:
            scheduler_step = torch.optim.lr_scheduler.MultiStepLR(
                optimizer, 
                milestones=milestones, 
                gamma=args.lr_gamma
            )
            multiplier = 8
            lr_scheduler = GradualWarmupScheduler(
                optimizer, 
                multiplier=multiplier,
                total_epoch=args.lr_warmup_epochs, 
                after_scheduler=scheduler_step
            )
        else: # no warmp, just multi-step
            lr_scheduler = torch.optim.lr_scheduler.MultiStepLR(
                optimizer, 
                milestones=milestones, 
                gamma=args.lr_gamma
            )
    else:
        lr_scheduler = None

    # Checkpointing
    if args.resume:
        ckpt_path = os.path.join(
            args.output_dir, 'checkpoints', 'checkpoint.pth')
        checkpoint = torch.load(ckpt_path, map_location='cpu')
        model_without_ddp.load_state_dict(checkpoint['model'])
        optimizer.load_state_dict(checkpoint['optimizer'])
        if lr_scheduler is not None:
            lr_scheduler.load_state_dict(checkpoint['lr_scheduler'])
        args.start_epoch = checkpoint['epoch']
        logger.info(f"Resuming from epoch: {args.start_epoch}")

    # Only perform evalaution
    if args.test_only:
        scores_val = evaluate(
            model, 
            data_loader_test,
            epoch=args.start_epoch, 
            writer=writer,
            ds=args.dataset,
        )
        _, vid_acc1, vid_acc5 = scores_val
        return vid_acc1, vid_acc5, args.start_epoch

    start_time = time.time()
    best_vid_acc_1 = -1
    best_vid_acc_5 = -1
    best_epoch = 0
    for epoch in range(args.start_epoch, args.epochs):
        logger.info(f'Start training epoch: {epoch}')
        scores = train(
            model, 
            optimizer, 
            data_loader,
            epoch, 
            writer=writer,
            ds=args.dataset,
        )
        logger.info(f'Start evaluating epoch: {epoch}')
        lr_scheduler.step()
        scores_val = evaluate(
            model, 
            data_loader_test,
            epoch=epoch,
            writer=writer,
            ds=args.dataset,
        )
        _, vid_acc1, vid_acc5 = scores_val
        training_stats.update(scores + scores_val)
        if vid_acc1 > best_vid_acc_1:
            best_vid_acc_1 = vid_acc1
            best_vid_acc_5 = vid_acc5
            best_epoch = epoch
        if args.output_dir:
            logger.info(f'Saving checkpoint to: {args.output_dir}')
            save_checkpoint(args, epoch, model, optimizer, lr_scheduler,
                ckpt_freq=1)
    total_time = time.time() - start_time
    total_time_str = str(datetime.timedelta(seconds=int(total_time)))
    logger.info(f'Training time {total_time_str}')
    return best_vid_acc_1, best_vid_acc_5, best_epoch