classifier.py

from classifier_utils import *


TQDM_DISABLE=True


class BertSentimentClassifier(torch.nn.Module):
    def __init__(self, config, custom_bert = None):
        super(BertSentimentClassifier, self).__init__()
        self.num_labels = config.num_labels
        self.bert: BertModel = custom_bert or BertModel.from_pretrained('bert-base-uncased')

        # Pretrain mode does not require updating BERT paramters.
        assert config.fine_tune_mode in ["last-linear-layer", "full-model"]
        for param in self.bert.parameters():
            if config.fine_tune_mode == 'last-linear-layer':
                param.requires_grad = False
            elif config.fine_tune_mode == 'full-model':
                param.requires_grad = True

        # Classifier = Dropout + Linear
        self.dropout = torch.nn.Dropout(config.hidden_dropout_prob)
        self.classifier = torch.nn.Linear(config.hidden_size, self.num_labels)


    def forward(self, input_ids, attention_mask):
        outputs = self.bert(input_ids, attention_mask)
        pooler_output = outputs['pooler_output']

        return self.classifier(self.dropout(pooler_output))


# Evaluate the model on dev examples.
def model_eval(dataloader, model: BertSentimentClassifier, device):
    model.eval() # Switch to eval model, will turn off randomness like dropout.
    y_true = []
    y_pred = []
    sents = []
    sent_ids = []
    for step, batch in enumerate(tqdm(dataloader, desc=f'eval', leave=False, disable=TQDM_DISABLE)):
        b_labels, b_sents, b_sent_ids = batch['labels'], batch['sents'], batch['sent_ids']

        b_ids = batch['token_ids'].to(device)
        b_mask = batch['attention_mask'].to(device)

        logits = model(b_ids, b_mask)
        logits = logits.detach().cpu().numpy()
        preds = np.argmax(logits, axis=1).flatten()

        b_labels = b_labels.flatten()
        y_true.extend(b_labels)
        y_pred.extend(preds)
        sents.extend(b_sents)
        sent_ids.extend(b_sent_ids)

    f1 = f1_score(y_true, y_pred, average='macro')
    acc = accuracy_score(y_true, y_pred)

    return acc, f1, y_pred, y_true, sents, sent_ids


# Evaluate the model on test examples.
def model_test_eval(dataloader, model, device):
    model.eval() # Switch to eval model, will turn off randomness like dropout.
    y_pred = []
    sents = []
    sent_ids = []
    for step, batch in enumerate(tqdm(dataloader, desc=f'eval', leave=False, disable=TQDM_DISABLE)):
        b_sents, b_sent_ids = batch['sents'], batch['sent_ids']

        b_ids = batch['token_ids'].to(device)
        b_mask = batch['attention_mask'].to(device)

        logits = model(b_ids, b_mask)
        logits = logits.detach().cpu().numpy()
        preds = np.argmax(logits, axis=1).flatten()

        y_pred.extend(preds)
        sents.extend(b_sents)
        sent_ids.extend(b_sent_ids)

    return y_pred, sents, sent_ids


def save_model(model, args, config, filepath):
    save_info = {
        'model': model.state_dict(),
        'args': args,
        'model_config': config,
        'system_rng': random.getstate(),
        'numpy_rng': np.random.get_state(),
        'torch_rng': torch.random.get_rng_state(),
    }

    torch.save(save_info, filepath)
    print(f"save the model to {filepath}")


def train(args, custom_bert=None):
    device = torch.device('cuda') if USE_GPU else torch.device('cpu')
    # Create the data and its corresponding datasets and dataloader.
    train_data, num_labels = load_data(args.train, 'train')
    dev_data = load_data(args.dev, 'valid')

    train_dataset = SentimentDataset(train_data)
    dev_dataset = SentimentDataset(dev_data)

    train_dataloader = DataLoader(train_dataset, shuffle=True, batch_size=args.batch_size,
                                  num_workers=NUM_CPU_CORES, collate_fn=train_dataset.collate_fn)
    dev_dataloader = DataLoader(dev_dataset, shuffle=False, batch_size=args.batch_size,
                                num_workers=NUM_CPU_CORES, collate_fn=dev_dataset.collate_fn)

    # Init model.
    config = {'hidden_dropout_prob': HIDDEN_DROPOUT_PROB,
              'num_labels': num_labels,
              'hidden_size': 768,
              'data_dir': '.',
              'fine_tune_mode': args.fine_tune_mode}

    config = SimpleNamespace(**config)

    model = BertSentimentClassifier(config, custom_bert)
    model = model.to(device)

    lr = args.lr
    optimizer = AdamW(model.parameters(), lr=lr)
    best_dev_acc = 0

    # Run for the specified number of epochs.
    for epoch in range(EPOCHS):
        model.train()
        train_loss = 0
        num_batches = 0
        for batch in tqdm(train_dataloader, desc=f'train-{epoch}', leave=False, disable=TQDM_DISABLE):
            b_ids = batch['token_ids'].to(device)
            b_mask = batch['attention_mask'].to(device)
            b_labels = batch['labels'].to(device)

            optimizer.zero_grad()
            logits = model(b_ids, b_mask)
            loss = F.cross_entropy(logits, b_labels.view(-1), reduction='sum') / args.batch_size

            loss.backward()
            optimizer.step()

            train_loss += loss.item()
            num_batches += 1

        train_loss = train_loss / (num_batches)

        train_acc, train_f1, *_  = model_eval(train_dataloader, model, device)
        dev_acc, dev_f1, *_ = model_eval(dev_dataloader, model, device)

        if dev_acc > best_dev_acc:
            best_dev_acc = dev_acc
            save_model(model, args, config, args.filepath)

        print(f"Epoch {epoch}: train loss :: {train_loss :.3f}, train acc :: {train_acc :.3f}, dev acc :: {dev_acc :.3f}")


def test(args):
    with torch.no_grad():
        device = torch.device('cuda') if USE_GPU else torch.device('cpu')
        saved = torch.load(args.filepath, weights_only=False)
        config = saved['model_config']
        model = BertSentimentClassifier(config)
        model.load_state_dict(saved['model'])
        model = model.to(device)
        print(f"load model from {args.filepath}")
        
        dev_data = load_data(args.dev, 'valid')
        dev_dataset = SentimentDataset(dev_data)
        dev_dataloader = DataLoader(dev_dataset, shuffle=False, batch_size=args.batch_size,
                                    num_workers=NUM_CPU_CORES, collate_fn=dev_dataset.collate_fn)

        dev_acc, dev_f1, dev_pred, dev_true, dev_sents, dev_sent_ids = model_eval(dev_dataloader, model, device)
        print('DONE DEV')
        print(f"dev acc :: {dev_acc :.3f}")


def classifier_run(args, custom_bert=None):
    seed_everything(SEED)
    torch.set_num_threads(NUM_CPU_CORES)
    
    print(f'Training Sentiment Classifier on {args.dataset}...')
    config = SimpleNamespace(
        filepath=f'{args.dataset}-classifier.pt',
        lr=args.lr,
        batch_size=args.batch_size,
        fine_tune_mode=args.fine_tune_mode,
        train=args.train, dev=args.dev, test=args.test,
        dev_out  = f'/predictions/{args.fine_tune_mode}-{args.dataset}-dev-out.csv',
        test_out = f'/predictions/{args.fine_tune_mode}-{args.dataset}-test-out.csv'
    )

    train(config, custom_bert)

    print(f'Evaluating on {args.dataset}...')
    test(config)