HuggingFace: ValueError: expected sequence of length 165 at dim 1 (got 128)
I am trying to fine-tune the BERT language model on my own data. I've gone through their docs, but their tasks seem to be not quite what I need, since my end goal is embedding text. Here's my code:
from datasets import load_dataset
from transformers import BertTokenizerFast, AutoModel, TrainingArguments, Trainer
import glob
import os


base_path = '../data/'
model_name = 'bert-base-uncased'
max_length = 512
checkpoints_dir = 'checkpoints'

tokenizer = BertTokenizerFast.from_pretrained(model_name, do_lower_case=True)


def tokenize_function(examples):
    return tokenizer(examples['text'], padding=True, truncation=True, max_length=max_length)


dataset = load_dataset('text',
        data_files={
            'train': f'{base_path}train.txt',
            'test': f'{base_path}test.txt',
            'validation': f'{base_path}valid.txt'
        }
)

print('Tokenizing data. This may take a while...')
tokenized_dataset = dataset.map(tokenize_function, batched=True)
train_dataset = tokenized_dataset['train']
eval_dataset = tokenized_dataset['test']

model = AutoModel.from_pretrained(model_name)

training_args = TrainingArguments(checkpoints_dir)

print('Training the model...')
trainer = Trainer(model=model, args=training_args, train_dataset=train_dataset, eval_dataset=eval_dataset)
trainer.train()

I get the following error:
  File &quot;train_lm_hf.py&quot;, line 44, in &lt;module&gt;
    trainer.train()
...
  File &quot;/opt/conda/lib/python3.7/site-packages/transformers/data/data_collator.py&quot;, line 130, in torch_default_data_collator
    batch[k] = torch.tensor([f[k] for f in features])
ValueError: expected sequence of length 165 at dim 1 (got 128)

What am I doing wrong?

I fixed this solution by changing the tokenize function to:
def tokenize_function(examples):
    return tokenizer(examples['text'], padding='max_length', truncation=True, max_length=max_length)

(note the padding argument). Also, I used a data collator like so:
data_collator = DataCollatorForLanguageModeling(
    tokenizer=tokenizer, mlm=True, mlm_probability=0.15
)
trainer = Trainer(
        model=model,
        args=training_args,
        data_collator=data_collator,
        train_dataset=train_dataset,
        eval_dataset=eval_dataset
)

