examples/tensorflow/translation/run_translation.py/main
def main():
    # region Argument parsing
    # See all possible arguments in src/transformers/training_args.py
    # or by passing the --help flag to this script.
    # We now keep distinct sets of args, for a cleaner separation of concerns.

    parser = HfArgumentParser((ModelArguments, DataTrainingArguments, TFTrainingArguments))
    if len(sys.argv) == 2 and sys.argv[1].endswith(".json"):
        # If we pass only one argument to the script and it's the path to a json file,
        # let's parse it to get our arguments.
        model_args, data_args, training_args = parser.parse_json_file(json_file=os.path.abspath(sys.argv[1]))
    else:
        model_args, data_args, training_args = parser.parse_args_into_dataclasses()
    # endregion

    # region Logging
    logging.basicConfig(
        format="%(asctime)s - %(levelname)s - %(name)s - %(message)s",
        datefmt="%m/%d/%Y %H:%M:%S",
        handlers=[logging.StreamHandler(sys.stdout)],
    )
    logger.setLevel(logging.INFO)
    datasets.utils.logging.set_verbosity(logging.INFO)
    transformers.utils.logging.set_verbosity(logging.INFO)

    # Log on each process the small summary:
    logger.info(f"Training/evaluation parameters {training_args}")
    # endregion

    # region Detecting last checkpoint
    last_checkpoint = None
    if os.path.isdir(training_args.output_dir) and training_args.do_train and not training_args.overwrite_output_dir:
        last_checkpoint = get_last_checkpoint(training_args.output_dir)
        if last_checkpoint is None and len(os.listdir(training_args.output_dir)) > 0:
            raise ValueError(
                f"Output directory ({training_args.output_dir}) already exists and is not empty. "
                "Use --overwrite_output_dir to overcome."
            )
        elif last_checkpoint is not None and training_args.resume_from_checkpoint is None:
            logger.info(
                f"Checkpoint detected, resuming training at {last_checkpoint}. To avoid this behavior, change "
                "the `--output_dir` or add `--overwrite_output_dir` to train from scratch."
            )
    # endregion

    # Set seed before initializing model.
    set_seed(training_args.seed)

    # region Load datasets
    # Get the datasets: you can either provide your own CSV/JSON training and evaluation files (see below)
    # or just provide the name of one of the public datasets available on the hub at https://huggingface.co/datasets/
    # (the dataset will be downloaded automatically from the datasets Hub).
    #
    # For CSV/JSON files this script will use the first column for the full texts and the second column for the
    # summaries (unless you specify column names for this with the `text_column` and `summary_column` arguments).
    #
    # In distributed training, the load_dataset function guarantee that only one local process can concurrently
    # download the dataset.
    if data_args.dataset_name is not None:
        # Downloading and loading a dataset from the hub.
        raw_datasets = load_dataset(
            data_args.dataset_name, data_args.dataset_config_name, cache_dir=model_args.cache_dir
        )
    else:
        data_files = {}
        if data_args.train_file is not None:
            data_files["train"] = data_args.train_file
            extension = data_args.train_file.split(".")[-1]
        if data_args.validation_file is not None:
            data_files["validation"] = data_args.validation_file
            extension = data_args.validation_file.split(".")[-1]
        raw_datasets = load_dataset(extension, data_files=data_files, cache_dir=model_args.cache_dir)
    # See more about loading any type of standard or custom dataset (from files, python dict, pandas DataFrame, etc) at
    # https://huggingface.co/docs/datasets/loading_datasets.html.
    # endregion

    # region Load model config and tokenizer
    #
    # Distributed training:
    # The .from_pretrained methods guarantee that only one local process can concurrently
    # download model & vocab.

    config = AutoConfig.from_pretrained(
        model_args.config_name if model_args.config_name else model_args.model_name_or_path,
        cache_dir=model_args.cache_dir,
        revision=model_args.model_revision,
        use_auth_token=True if model_args.use_auth_token else None,
    )
    tokenizer = AutoTokenizer.from_pretrained(
        model_args.tokenizer_name if model_args.tokenizer_name else model_args.model_name_or_path,
        cache_dir=model_args.cache_dir,
        use_fast=model_args.use_fast_tokenizer,
        revision=model_args.model_revision,
        use_auth_token=True if model_args.use_auth_token else None,
    )

    prefix = data_args.source_prefix if data_args.source_prefix is not None else ""
    # endregion

    # region Dataset preprocessing
    # We need to tokenize inputs and targets.
    if training_args.do_train:
        column_names = raw_datasets["train"].column_names
    elif training_args.do_eval:
        column_names = raw_datasets["validation"].column_names
    else:
        logger.info("There is nothing to do. Please pass `do_train`, and/or `do_eval`.")
        return

    column_names = raw_datasets["train"].column_names

    # For translation we set the codes of our source and target languages (only useful for mBART, the others will
    # ignore those attributes).
    if isinstance(tokenizer, tuple(MULTILINGUAL_TOKENIZERS)):
        assert data_args.target_lang is not None and data_args.source_lang is not None, (
            f"{tokenizer.__class__.__name__} is a multilingual tokenizer which requires --source_lang and "
            "--target_lang arguments."
        )
        tokenizer.src_lang = data_args.source_lang
        tokenizer.tgt_lang = data_args.target_lang
        forced_bos_token_id = (
            tokenizer.lang_code_to_id[data_args.forced_bos_token] if data_args.forced_bos_token is not None else None
        )

    # Get the language codes for input/target.
    source_lang = data_args.source_lang.split("_")[0]
    target_lang = data_args.target_lang.split("_")[0]

    padding = "max_length" if data_args.pad_to_max_length else False

    # Temporarily set max_target_length for training.
    max_target_length = data_args.max_target_length
    padding = "max_length" if data_args.pad_to_max_length else False

    def preprocess_function(examples):
        inputs = [ex[source_lang] for ex in examples["translation"]]
        targets = [ex[target_lang] for ex in examples["translation"]]
        inputs = [prefix + inp for inp in inputs]
        model_inputs = tokenizer(inputs, max_length=data_args.max_source_length, padding=padding, truncation=True)

        # Setup the tokenizer for targets
        with tokenizer.as_target_tokenizer():
            labels = tokenizer(targets, max_length=max_target_length, padding=padding, truncation=True)

        # If we are padding here, replace all tokenizer.pad_token_id in the labels by -100 when we want to ignore
        # padding in the loss.
        if padding == "max_length" and data_args.ignore_pad_token_for_loss:
            labels["input_ids"] = [
                [(l if l != tokenizer.pad_token_id else -100) for l in label] for label in labels["input_ids"]
            ]

        model_inputs["labels"] = labels["input_ids"]
        return model_inputs

    if training_args.do_train:
        if "train" not in raw_datasets:
            raise ValueError("--do_train requires a train dataset")
        train_dataset = raw_datasets["train"]
        if data_args.max_train_samples is not None:
            train_dataset = train_dataset.select(range(data_args.max_train_samples))
        with training_args.main_process_first(desc="train dataset map pre-processing"):
            train_dataset = train_dataset.map(
                preprocess_function,
                batched=True,
                num_proc=data_args.preprocessing_num_workers,
                remove_columns=column_names,
                load_from_cache_file=not data_args.overwrite_cache,
                desc="Running tokenizer on train dataset",
            )
    else:
        train_dataset = None

    if training_args.do_eval:
        max_target_length = data_args.val_max_target_length
        if "validation" not in raw_datasets:
            raise ValueError("--do_eval requires a validation dataset")
        eval_dataset = raw_datasets["validation"]
        if data_args.max_eval_samples is not None:
            eval_dataset = eval_dataset.select(range(data_args.max_eval_samples))
        with training_args.main_process_first(desc="validation dataset map pre-processing"):
            eval_dataset = eval_dataset.map(
                preprocess_function,
                batched=True,
                num_proc=data_args.preprocessing_num_workers,
                remove_columns=column_names,
                load_from_cache_file=not data_args.overwrite_cache,
                desc="Running tokenizer on validation dataset",
            )
    else:
        eval_dataset = None
    # endregion

    with training_args.strategy.scope():
        # region Prepare model
        model = TFAutoModelForSeq2SeqLM.from_pretrained(
            model_args.model_name_or_path,
            config=config,
            cache_dir=model_args.cache_dir,
            revision=model_args.model_revision,
            use_auth_token=True if model_args.use_auth_token else None,
        )

        model.resize_token_embeddings(len(tokenizer))
        if isinstance(tokenizer, tuple(MULTILINGUAL_TOKENIZERS)):
            model.config.forced_bos_token_id = forced_bos_token_id
        # endregion

        # region Set decoder_start_token_id
        if model.config.decoder_start_token_id is None and isinstance(tokenizer, (MBartTokenizer, MBartTokenizerFast)):
            assert (
                data_args.target_lang is not None and data_args.source_lang is not None
            ), "mBart requires --target_lang and --source_lang"
            if isinstance(tokenizer, MBartTokenizer):
                model.config.decoder_start_token_id = tokenizer.lang_code_to_id[data_args.target_lang]
            else:
                model.config.decoder_start_token_id = tokenizer.convert_tokens_to_ids(data_args.target_lang)

        if model.config.decoder_start_token_id is None:
            raise ValueError("Make sure that `config.decoder_start_token_id` is correctly defined")
        # endregion

        # region Prepare TF Dataset objects
        num_replicas = training_args.strategy.num_replicas_in_sync
        total_train_batch_size = training_args.per_device_train_batch_size * num_replicas
        total_eval_batch_size = training_args.per_device_eval_batch_size * num_replicas
        tf_train_dataset = dataset_to_tf(
            train_dataset,
            model,
            tokenizer,
            total_batch_size=total_train_batch_size,
            num_epochs=training_args.num_train_epochs,
            shuffle=True,
        )
        tf_eval_dataset = dataset_to_tf(
            eval_dataset,
            model,
            tokenizer,
            total_eval_batch_size,
            num_epochs=1,
            shuffle=False,
        )
        # endregion

        # region Optimizer, loss and LR scheduling
        # Scheduler and math around the number of training steps.
        num_update_steps_per_epoch = len(train_dataset) // training_args.per_device_train_batch_size
        num_train_steps = training_args.num_train_epochs * num_update_steps_per_epoch
        optimizer, lr_schedule = create_optimizer(
            init_lr=training_args.learning_rate,
            num_train_steps=num_train_steps,
            num_warmup_steps=training_args.warmup_steps,
        )

        def masked_sparse_categorical_crossentropy(y_true, y_pred):
            # We clip the negative labels to 0 to avoid NaNs appearing in the output and
            # fouling up everything that comes afterwards. The loss values corresponding to clipped values
            # will be masked later anyway, but even masked NaNs seem to cause overflows for some reason.
            # 1e6 is chosen as a reasonable upper bound for the number of token indices - in the unlikely
            # event that you have more than 1 million tokens in your vocabulary, consider increasing this value.
            # More pragmatically, consider redesigning your tokenizer.
            losses = tf.keras.losses.sparse_categorical_crossentropy(
                tf.clip_by_value(y_true, 0, int(1e6)), y_pred, from_logits=True
            )
            # Compute the per-sample loss only over the unmasked tokens
            losses = tf.ragged.boolean_mask(losses, y_true != -100)
            losses = tf.reduce_mean(losses, axis=-1)
            return losses

        # endregion

        # region Metric and postprocessing
        metric = load_metric("sacrebleu")

        def postprocess_text(preds, labels):
            preds = [pred.strip() for pred in preds]
            labels = [[label.strip()] for label in labels]

            return preds, labels

        # endregion

        # region Training
        model.compile(loss={"logits": masked_sparse_categorical_crossentropy}, optimizer=optimizer)

        if training_args.do_train:
            logger.info("***** Running training *****")
            logger.info(f"  Num examples = {len(train_dataset)}")
            logger.info(f"  Num Epochs = {training_args.num_train_epochs}")
            logger.info(f"  Instantaneous batch size per device = {training_args.per_device_train_batch_size}")
            logger.info(f"  Total train batch size = {total_train_batch_size}")
            logger.info(f"  Total optimization steps = {num_train_steps}")

            model.fit(
                tf_train_dataset,
                epochs=int(training_args.num_train_epochs),
                steps_per_epoch=num_update_steps_per_epoch,
            )
        # endregion

        # region Validation
        if data_args.val_max_target_length is None:
            data_args.val_max_target_length = data_args.max_target_length

        gen_kwargs = {
            "max_length": data_args.val_max_target_length,
            "num_beams": data_args.num_beams,
        }
        if training_args.do_eval:
            logger.info("Evaluation...")
            for batch, labels in tqdm(
                tf_eval_dataset, total=len(eval_dataset) // training_args.per_device_eval_batch_size
            ):
                batch.update(gen_kwargs)
                generated_tokens = model.generate(**batch)
                if isinstance(generated_tokens, tuple):
                    generated_tokens = generated_tokens[0]
                decoded_preds = tokenizer.batch_decode(generated_tokens, skip_special_tokens=True)
                labels = np.where(labels != -100, labels, tokenizer.pad_token_id)
                decoded_labels = tokenizer.batch_decode(labels, skip_special_tokens=True)
                decoded_preds, decoded_labels = postprocess_text(decoded_preds, decoded_labels)

                metric.add_batch(predictions=decoded_preds, references=decoded_labels)
            eval_metric = metric.compute()
            logger.info({"bleu": eval_metric["score"]})
        # endregion

        if training_args.output_dir is not None:
            model.save_pretrained(training_args.output_dir)