def main()

in main.py [0:0]


def main():

    # parse arguments
    global args
    parser = parse_arguments()
    args = parser.parse_args()

    # exp setup: logger, distributed mode and seeds
    init_distributed_mode(args)
    init_signal_handler()
    fix_random_seeds(args.seed)
    logger, training_stats = initialize_exp(args, "epoch", "loss")
    if args.rank == 0:
        writer = SummaryWriter(args.dump_path)
    else:
        writer = None

    # build data
    train_dataset = AVideoDataset(
        ds_name=args.ds_name,
        root_dir=args.root_dir,
        mode='train',
        path_to_data_dir=args.data_path,
        num_frames=args.num_frames,
        target_fps=args.target_fps,
        sample_rate=args.sample_rate,
        num_train_clips=args.num_train_clips,
        train_crop_size=args.train_crop_size,
        test_crop_size=args.test_crop_size,
        num_data_samples=args.num_data_samples,
        colorjitter=args.colorjitter,
        use_grayscale=args.use_grayscale,
        use_gaussian=args.use_gaussian,
        temp_jitter=True,
        decode_audio=True,
        aug_audio=None,
        num_sec=args.num_sec_aud,
        aud_sample_rate=args.aud_sample_rate,
        aud_spec_type=args.aud_spec_type,
        use_volume_jittering=args.use_volume_jittering,
        use_temporal_jittering=args.use_audio_temp_jittering,
        z_normalize=args.z_normalize,
        dual_data=args.dual_data
    )
    sampler = torch.utils.data.distributed.DistributedSampler(train_dataset)
    train_loader = torch.utils.data.DataLoader(
        train_dataset,
        sampler=sampler,
        batch_size=args.batch_size,
        num_workers=args.workers,
        pin_memory=True,
        drop_last=True
    )
    logger.info("Loaded data with {} videos.".format(len(train_dataset)))

    # Load model
    model = load_model(
        vid_base_arch=args.vid_base_arch,
        aud_base_arch=args.aud_base_arch,
        use_mlp=args.use_mlp,
        num_classes=args.mlp_dim,
        pretrained=False,
        norm_feat=False,
        use_max_pool=False,
        headcount=args.headcount,
    )

    # synchronize batch norm layers
    if args.sync_bn == "pytorch":
        model = nn.SyncBatchNorm.convert_sync_batchnorm(model)
    elif args.sync_bn == "apex":
        process_group = None
        if args.world_size // 8 > 0:
            process_group = apex.parallel.create_syncbn_process_group(args.world_size // 8)
        model = apex.parallel.convert_syncbn_model(model, process_group=process_group)

    # copy model to GPU
    model = model.cuda()
    if args.rank == 0:
        logger.info(model)
    logger.info("Building model done.")

    # build optimizer
    optimizer = torch.optim.SGD(
        model.parameters(),
        lr=args.base_lr,
        momentum=0.9,
        weight_decay=args.wd,
    )
    if args.use_warmup_scheduler:
        lr_scheduler = GradualWarmupScheduler(
            optimizer,
            multiplier=args.world_size,
            total_epoch=args.warmup_epochs,
            after_scheduler=None
        )
    else:
        lr_scheduler = None

    logger.info("Building optimizer done.")

    # init mixed precision
    if args.use_fp16:
        model, optimizer = apex.amp.initialize(model, optimizer, opt_level="O1")
        logger.info("Initializing mixed precision done.")

    # wrap model
    model = nn.parallel.DistributedDataParallel(
        model,
        device_ids=[args.gpu_to_work_on],
        find_unused_parameters=True,
    )

    # SK-Init
    N_dl = len(train_loader)
    N = len(train_loader.dataset)
    N_distr = N_dl * train_loader.batch_size
    selflabels = torch.zeros((N, args.headcount), dtype=torch.long, device='cuda')
    global sk_schedule
    sk_schedule = (args.epochs * N_dl * (np.linspace(0, 1, args.nopts) ** args.schedulepower)[::-1]).tolist()
    # to make sure we don't make it empty
    sk_schedule = [(args.epochs + 2) * N_dl] + sk_schedule
    logger.info(f'remaining SK opts @ epochs {[np.round(1.0 * t / N_dl, 2) for t in sk_schedule]}')

    # optionally resume from a checkpoint
    to_restore = {"epoch": 0, 'selflabels': selflabels, 'dist':args.dist}
    restart_from_checkpoint(
        os.path.join(args.dump_path, "checkpoint.pth.tar"),
        run_variables=to_restore,
        model=model,
        optimizer=optimizer,
        amp=apex.amp if args.use_fp16 else None,
    )
    start_epoch = to_restore["epoch"]
    selflabels = to_restore["selflabels"]
    args.dist = to_restore["dist"]

    # Set CuDNN benhcmark
    cudnn.benchmark = True

    # Restart schedule correctly
    if start_epoch != 0:
        include = [(qq / N_dl > start_epoch) for qq in sk_schedule]
        # (total number of sk-opts) - (number of sk-opts outstanding)
        global sk_counter
        sk_counter = len(sk_schedule) - sum(include)
        sk_schedule = (np.array(sk_schedule)[include]).tolist()
        if lr_scheduler:
            [lr_scheduler.step() for _ in range(to_restore['epoch'])]

    if start_epoch == 0:
        train_loader.sampler.set_epoch(999)
        warmup_batchnorm(args, model, train_loader, batches=20, group=group)

    for epoch in range(start_epoch, args.epochs):

        # train the network for one epoch
        logger.info("============ Starting epoch %i ... ============" % epoch)
        if writer:
            writer.add_scalar('train/epoch', epoch, epoch)

        # set sampler
        train_loader.sampler.set_epoch(epoch)

        # train the network
        scores, selflabels = train(
            train_loader, model, optimizer, epoch, writer, selflabels)
        training_stats.update(scores)

        # Update LR scheduler
        if lr_scheduler:
            lr_scheduler.step()

        # save checkpoints
        if args.rank == 0:
            save_dict = {
                "epoch": epoch + 1,
                "dist": args.dist,
                "model": model.state_dict(),
                "optimizer": optimizer.state_dict(),
                "selflabels": selflabels
            }

            if args.use_fp16:
                save_dict["amp"] = apex.amp.state_dict()
            torch.save(
                save_dict,
                os.path.join(args.dump_path, "checkpoint.pth.tar"),
            )
            if epoch % args.checkpoint_freq == 0 or epoch == args.epochs - 1:
                shutil.copyfile(
                    os.path.join(args.dump_path, "checkpoint.pth.tar"),
                    os.path.join(args.dump_checkpoints, "ckp-" + str(epoch) + ".pth")
                )