train.py

# Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

from functools import partial
import argparse
import os
import random
import time

import numpy as np
import paddle
import paddle.nn.functional as F

from paddlenlp.data import Stack, Tuple, Pad
import paddlenlp as ppnlp

MODEL_CLASSES = {
    "bert": (ppnlp.transformers.BertForSequenceClassification,
             ppnlp.transformers.BertTokenizer),
    'ernie': (ppnlp.transformers.ErnieForSequenceClassification,
              ppnlp.transformers.ErnieTokenizer),
    'roberta': (ppnlp.transformers.RobertaForSequenceClassification,
                ppnlp.transformers.RobertaTokenizer),
}


def parse_args():
    parser = argparse.ArgumentParser()
    # Required parameters
    parser.add_argument(
        "--model_type",
        default='ernie',
        required=True,
        type=str,
        help="Model type selected in the list: " +
        ", ".join(MODEL_CLASSES.keys()))
    parser.add_argument(
        "--model_name",
        default='ernie-tiny',
        required=True,
        type=str,
        help="Path to pre-trained model or shortcut name selected in the list: "
        + ", ".join(
            sum([
                list(classes[-1].pretrained_init_configuration.keys())
                for classes in MODEL_CLASSES.values()
            ], [])))
    parser.add_argument(
        "--save_dir",
        default='./checkpoint',
        required=True,
        type=str,
        help="The output directory where the model checkpoints will be written.")

    parser.add_argument(
        "--max_seq_length",
        default=128,
        type=int,
        help="The maximum total input sequence length after tokenization. "
        "Sequences longer than this will be truncated, sequences shorter will be padded."
    )
    parser.add_argument(
        "--batch_size",
        default=32,
        type=int,
        help="Batch size per GPU/CPU for training.")
    parser.add_argument(
        "--learning_rate",
        default=5e-5,
        type=float,
        help="The initial learning rate for Adam.")
    parser.add_argument(
        "--weight_decay",
        default=0.0,
        type=float,
        help="Weight decay if we apply some.")
    parser.add_argument(
        "--epochs",
        default=3,
        type=int,
        help="Total number of training epochs to perform.")
    parser.add_argument(
        "--warmup_proption",
        default=0.0,
        type=float,
        help="Linear warmup proption over the training process.")
    parser.add_argument(
        "--init_from_ckpt",
        type=str,
        default=None,
        help="The path of checkpoint to be loaded.")
    parser.add_argument(
        "--seed", type=int, default=1000, help="random seed for initialization")
    parser.add_argument(
        "--n_gpu",
        type=int,
        default=1,
        help="Number of GPUs to use, 0 for CPU.")
    args = parser.parse_args()
    return args


def set_seed(args):
    """sets random seed"""
    random.seed(args.seed)
    np.random.seed(args.seed)
    paddle.seed(args.seed)


@paddle.no_grad()
def evaluate(model, criterion, metric, data_loader):
    """
    Given a dataset, it evals model and computes the metric.

    Args:
        model(obj:`paddle.nn.Layer`): A model to classify texts.
        data_loader(obj:`paddle.io.DataLoader`): The dataset loader which generates batches.
        criterion(obj:`paddle.nn.Layer`): It can compute the loss.
        metric(obj:`paddle.metric.Metric`): The evaluation metric.
    """
    model.eval()
    metric.reset()
    losses = []
    for batch in data_loader:
        input_ids, segment_ids, labels = batch
        logits = model(input_ids, segment_ids)
        loss = criterion(logits, labels)
        losses.append(loss.numpy())
        correct = metric.compute(logits, labels)
        metric.update(correct)
        accu = metric.accumulate()
    print("eval loss: %.5f, accu: %.5f" % (np.mean(losses), accu))
    model.train()
    metric.reset()


def convert_example(example,
                    tokenizer,
                    label_list,
                    max_seq_length=512,
                    is_test=False):
    """
    Builds model inputs from a sequence or a pair of sequence for sequence classification tasks
    by concatenating and adding special tokens. And creates a mask from the two sequences passed 
    to be used in a sequence-pair classification task.
        
    A BERT sequence has the following format:

    - single sequence: ``[CLS] X [SEP]``
    - pair of sequences: ``[CLS] A [SEP] B [SEP]``

    A BERT sequence pair mask has the following format:
    ::
        0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1
        | first sequence    | second sequence |

    If only one sequence, only returns the first portion of the mask (0's).


    Args:
        example(obj:`list[str]`): List of input data, containing text and label if it have label.
        tokenizer(obj:`PretrainedTokenizer`): This tokenizer inherits from :class:`~paddlenlp.transformers.PretrainedTokenizer` 
            which contains most of the methods. Users should refer to the superclass for more information regarding methods.
        label_list(obj:`list[str]`): All the labels that the data has.
        max_seq_len(obj:`int`): The maximum total input sequence length after tokenization. 
            Sequences longer than this will be truncated, sequences shorter will be padded.
        is_test(obj:`False`, defaults to `False`): Whether the example contains label or not.

    Returns:
        input_ids(obj:`list[int]`): The list of token ids.
        segment_ids(obj: `list[int]`): List of sequence pair mask.
        label(obj:`numpy.array`, data type of int64, optional): The input label if not is_test.
    """
    text, label = example
    encoded_inputs = tokenizer.encode(text=text, max_seq_len=max_seq_length)
    input_ids = encoded_inputs["input_ids"]
    segment_ids = encoded_inputs["segment_ids"]

    if not is_test:
        #create label maps if classification task
        if label_list:
            label_map = {}
            for (i, l) in enumerate(label_list):
                label_map[l] = i
            label = label_map[label]
        label = np.array([label], dtype="int64")
        return input_ids, segment_ids, label
    else:
        return input_ids, segment_ids


def create_dataloader(dataset,
                      mode='train',
                      batch_size=1,
                      batchify_fn=None,
                      trans_fn=None):
    if trans_fn:
        dataset = dataset.apply(trans_fn, lazy=True)

    shuffle = True if mode == 'train' else False
    if mode == 'train':
        batch_sampler = paddle.io.DistributedBatchSampler(
            dataset, batch_size=batch_size, shuffle=shuffle)
    else:
        batch_sampler = paddle.io.BatchSampler(
            dataset, batch_size=batch_size, shuffle=shuffle)

    return paddle.io.DataLoader(
        dataset=dataset,
        batch_sampler=batch_sampler,
        collate_fn=batchify_fn,
        return_list=True)


def do_train(args):
    set_seed(args)
    paddle.set_device("gpu" if args.n_gpu else "cpu")
    world_size = paddle.distributed.get_world_size()
    if world_size > 1:
        paddle.distributed.init_parallel_env()

    args.model_type = args.model_type.lower()
    model_class, tokenizer_class = MODEL_CLASSES[args.model_type]

    train_dataset, dev_dataset, test_dataset = ppnlp.datasets.ChnSentiCorp.get_datasets(
        ['train', 'dev', 'test'])
    if args.model_name == 'ernie_tiny':
        # ErnieTinyTokenizer is special for ernie_tiny pretained model.
        tokenizer = ppnlp.transformers.ErnieTinyTokenizer.from_pretrained(
            args.model_name)
    else:
        tokenizer = tokenizer_class.from_pretrained(args.model_name)

    trans_func = partial(
        convert_example,
        tokenizer=tokenizer,
        label_list=train_dataset.get_labels(),
        max_seq_length=args.max_seq_length)
    batchify_fn = lambda samples, fn=Tuple(
        Pad(axis=0, pad_val=tokenizer.pad_token_id),  # input
        Pad(axis=0, pad_val=tokenizer.pad_token_id),  # segment
        Stack(dtype="int64")  # label
    ): [data for data in fn(samples)]
    train_data_loader = create_dataloader(
        train_dataset,
        mode='train',
        batch_size=args.batch_size,
        batchify_fn=batchify_fn,
        trans_fn=trans_func)
    dev_data_loader = create_dataloader(
        dev_dataset,
        mode='dev',
        batch_size=args.batch_size,
        batchify_fn=batchify_fn,
        trans_fn=trans_func)
    test_data_loader = create_dataloader(
        test_dataset,
        mode='test',
        batch_size=args.batch_size,
        batchify_fn=batchify_fn,
        trans_fn=trans_func)

    model = model_class.from_pretrained(
        args.model_name, num_classes=len(train_dataset.get_labels()))

    if args.init_from_ckpt and os.path.isfile(args.init_from_ckpt):
        state_dict = paddle.load(args.init_from_ckpt)
        model.set_dict(state_dict)
    model = paddle.DataParallel(model)

    num_training_steps = len(train_data_loader) * args.epochs
    num_warmup_steps = int(args.warmup_proption * num_training_steps)

    def get_lr_factor(current_step):
        if current_step < num_warmup_steps:
            return float(current_step) / float(max(1, num_warmup_steps))
        else:
            return max(0.0,
                       float(num_training_steps - current_step) /
                       float(max(1, num_training_steps - num_warmup_steps)))

    lr_scheduler = paddle.optimizer.lr.LambdaDecay(
        args.learning_rate,
        lr_lambda=lambda current_step: get_lr_factor(current_step))
    optimizer = paddle.optimizer.AdamW(
        learning_rate=lr_scheduler,
        parameters=model.parameters(),
        weight_decay=args.weight_decay,
        apply_decay_param_fun=lambda x: x in [
            p.name for n, p in model.named_parameters()
            if not any(nd in n for nd in ["bias", "norm"])
        ])

    criterion = paddle.nn.loss.CrossEntropyLoss()
    metric = paddle.metric.Accuracy()

    global_step = 0
    tic_train = time.time()
    for epoch in range(1, args.epochs + 1):
        for step, batch in enumerate(train_data_loader, start=1):
            input_ids, segment_ids, labels = batch
            logits = model(input_ids, segment_ids)
            loss = criterion(logits, labels)
            probs = F.softmax(logits, axis=1)
            correct = metric.compute(probs, labels)
            metric.update(correct)
            acc = metric.accumulate()

            global_step += 1
            if global_step % 10 == 0 and paddle.distributed.get_rank() == 0:
                print(
                    "global step %d, epoch: %d, batch: %d, loss: %.5f, accu: %.5f, speed: %.2f step/s"
                    % (global_step, epoch, step, loss, acc,
                       10 / (time.time() - tic_train)))
                tic_train = time.time()
            loss.backward()
            optimizer.step()
            lr_scheduler.step()
            optimizer.clear_gradients()
            if global_step % 100 == 0 and paddle.distributed.get_rank() == 0:
                save_dir = os.path.join(args.save_dir, "model_%d" % global_step)
                if not os.path.exists(save_dir):
                    os.makedirs(save_dir)
                evaluate(model, criterion, metric, dev_data_loader)
                model._layers.save_pretrained(save_dir)
                tokenizer.save_pretrained(save_dir)

    if paddle.distributed.get_rank() == 0:
        print('Evaluating on test data.')
        evaluate(model, criterion, metric, test_data_loader)


if __name__ == "__main__":
    args = parse_args()
    if args.n_gpu > 1:
        paddle.distributed.spawn(do_train, args=(args, ), nprocs=args.n_gpu)
    else:
        do_train(args)