Finetune 🤗 Transformers Models with PyTorch Lightning ⚡¶
This notebook will use HuggingFace's datasets library to get data, which will be wrapped in a LightningDataModule. Then, we write a class to perform text classification on any dataset from the GLUE Benchmark. (We just show CoLA and MRPC due to constraint on compute/disk)
HuggingFace's NLP Viewer can help you get a feel for the two datasets we will use and what tasks they are solving for.
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Setup¶
In [ ]:
!pip install pytorch-lightning datasets transformers
In [2]:
from argparse import ArgumentParser
from datetime import datetime
from typing import Optional
import datasets
import numpy as np
import pytorch_lightning as pl
import torch
from torch.utils.data import DataLoader
from transformers import (
AdamW,
AutoModelForSequenceClassification,
AutoConfig,
AutoTokenizer,
get_linear_schedule_with_warmup,
glue_compute_metrics
)
GLUE DataModule¶
In [3]:
class GLUEDataModule(pl.LightningDataModule):
task_text_field_map = {
'cola': ['sentence'],
'sst2': ['sentence'],
'mrpc': ['sentence1', 'sentence2'],
'qqp': ['question1', 'question2'],
'stsb': ['sentence1', 'sentence2'],
'mnli': ['premise', 'hypothesis'],
'qnli': ['question', 'sentence'],
'rte': ['sentence1', 'sentence2'],
'wnli': ['sentence1', 'sentence2'],
'ax': ['premise', 'hypothesis']
}
glue_task_num_labels = {
'cola': 2,
'sst2': 2,
'mrpc': 2,
'qqp': 2,
'stsb': 1,
'mnli': 3,
'qnli': 2,
'rte': 2,
'wnli': 2,
'ax': 3
}
loader_columns = [
'datasets_idx',
'input_ids',
'token_type_ids',
'attention_mask',
'start_positions',
'end_positions',
'labels'
]
def __init__(
self,
model_name_or_path: str,
task_name: str ='mrpc',
max_seq_length: int = 128,
train_batch_size: int = 32,
eval_batch_size: int = 32,
**kwargs
):
super().__init__()
self.model_name_or_path = model_name_or_path
self.task_name = task_name
self.max_seq_length = max_seq_length
self.train_batch_size = train_batch_size
self.eval_batch_size = eval_batch_size
self.text_fields = self.task_text_field_map[task_name]
self.num_labels = self.glue_task_num_labels[task_name]
self.tokenizer = AutoTokenizer.from_pretrained(self.model_name_or_path, use_fast=True)
def setup(self, stage):
self.dataset = datasets.load_dataset('glue', self.task_name)
for split in self.dataset.keys():
self.dataset[split] = self.dataset[split].map(
self.convert_to_features,
batched=True,
remove_columns=['label'],
)
self.columns = [c for c in self.dataset[split].column_names if c in self.loader_columns]
self.dataset[split].set_format(type="torch", columns=self.columns)
self.eval_splits = [x for x in self.dataset.keys() if 'validation' in x]
def prepare_data(self):
datasets.load_dataset('glue', self.task_name)
AutoTokenizer.from_pretrained(self.model_name_or_path, use_fast=True)
def train_dataloader(self):
return DataLoader(self.dataset['train'], batch_size=self.train_batch_size)
def val_dataloader(self):
if len(self.eval_splits) == 1:
return DataLoader(self.dataset['validation'], batch_size=self.eval_batch_size)
elif len(self.eval_splits) > 1:
return [DataLoader(self.dataset[x], batch_size=self.eval_batch_size) for x in self.eval_splits]
def test_dataloader(self):
if len(self.eval_splits) == 1:
return DataLoader(self.dataset['test'], batch_size=self.eval_batch_size)
elif len(self.eval_splits) > 1:
return [DataLoader(self.dataset[x], batch_size=self.eval_batch_size) for x in self.eval_splits]
def convert_to_features(self, example_batch, indices=None):
# Either encode single sentence or sentence pairs
if len(self.text_fields) > 1:
texts_or_text_pairs = list(zip(example_batch[self.text_fields[0]], example_batch[self.text_fields[1]]))
else:
texts_or_text_pairs = example_batch[self.text_fields[0]]
# Tokenize the text/text pairs
features = self.tokenizer.batch_encode_plus(
texts_or_text_pairs,
max_length=self.max_seq_length,
pad_to_max_length=True,
truncation=True
)
# Rename label to labels to make it easier to pass to model forward
features['labels'] = example_batch['label']
return features
You could use this datamodule with standalone PyTorch if you wanted...¶
In [ ]:
dm = GLUEDataModule('distilbert-base-uncased')
dm.prepare_data()
dm.setup('fit')
next(iter(dm.train_dataloader()))
GLUE Model¶
In [5]:
class GLUETransformer(pl.LightningModule):
def __init__(
self,
model_name_or_path: str,
num_labels: int,
learning_rate: float = 2e-5,
adam_epsilon: float = 1e-8,
warmup_steps: int = 0,
weight_decay: float = 0.0,
train_batch_size: int = 32,
eval_batch_size: int = 32,
eval_splits: Optional[list] = None,
**kwargs
):
super().__init__()
self.save_hyperparameters()
self.config = AutoConfig.from_pretrained(model_name_or_path, num_labels=num_labels)
self.model = AutoModelForSequenceClassification.from_pretrained(model_name_or_path, config=self.config)
self.metric = datasets.load_metric(
'glue',
self.hparams.task_name,
experiment_id=datetime.now().strftime("%d-%m-%Y_%H-%M-%S")
)
def forward(self, **inputs):
return self.model(**inputs)
def training_step(self, batch, batch_idx):
outputs = self(**batch)
loss = outputs[0]
return loss
def validation_step(self, batch, batch_idx, dataloader_idx=0):
outputs = self(**batch)
val_loss, logits = outputs[:2]
if self.hparams.num_labels >= 1:
preds = torch.argmax(logits, axis=1)
elif self.hparams.num_labels == 1:
preds = logits.squeeze()
labels = batch["labels"]
return {'loss': val_loss, "preds": preds, "labels": labels}
def validation_epoch_end(self, outputs):
if self.hparams.task_name == 'mnli':
for i, output in enumerate(outputs):
# matched or mismatched
split = self.hparams.eval_splits[i].split('_')[-1]
preds = torch.cat([x['preds'] for x in output]).detach().cpu().numpy()
labels = torch.cat([x['labels'] for x in output]).detach().cpu().numpy()
loss = torch.stack([x['loss'] for x in output]).mean()
self.log(f'val_loss_{split}', loss, prog_bar=True)
split_metrics = {f"{k}_{split}": v for k, v in self.metric.compute(predictions=preds, references=labels).items()}
self.log_dict(split_metrics, prog_bar=True)
return loss
preds = torch.cat([x['preds'] for x in outputs]).detach().cpu().numpy()
labels = torch.cat([x['labels'] for x in outputs]).detach().cpu().numpy()
loss = torch.stack([x['loss'] for x in outputs]).mean()
self.log('val_loss', loss, prog_bar=True)
self.log_dict(self.metric.compute(predictions=preds, references=labels), prog_bar=True)
return loss
def setup(self, stage):
if stage == 'fit':
# Get dataloader by calling it - train_dataloader() is called after setup() by default
train_loader = self.train_dataloader()
# Calculate total steps
self.total_steps = (
(len(train_loader.dataset) // (self.hparams.train_batch_size * max(1, self.hparams.gpus)))
// self.hparams.accumulate_grad_batches
* float(self.hparams.max_epochs)
)
def configure_optimizers(self):
"Prepare optimizer and schedule (linear warmup and decay)"
model = self.model
no_decay = ["bias", "LayerNorm.weight"]
optimizer_grouped_parameters = [
{
"params": [p for n, p in model.named_parameters() if not any(nd in n for nd in no_decay)],
"weight_decay": self.hparams.weight_decay,
},
{
"params": [p for n, p in model.named_parameters() if any(nd in n for nd in no_decay)],
"weight_decay": 0.0,
},
]
optimizer = AdamW(optimizer_grouped_parameters, lr=self.hparams.learning_rate, eps=self.hparams.adam_epsilon)
scheduler = get_linear_schedule_with_warmup(
optimizer, num_warmup_steps=self.hparams.warmup_steps, num_training_steps=self.total_steps
)
scheduler = {
'scheduler': scheduler,
'interval': 'step',
'frequency': 1
}
return [optimizer], [scheduler]
@staticmethod
def add_model_specific_args(parent_parser):
parser = ArgumentParser(parents=[parent_parser], add_help=False)
parser.add_argument("--learning_rate", default=2e-5, type=float)
parser.add_argument("--adam_epsilon", default=1e-8, type=float)
parser.add_argument("--warmup_steps", default=0, type=int)
parser.add_argument("--weight_decay", default=0.0, type=float)
return parser
⚡ Quick Tip¶
- Combine arguments from your DataModule, Model, and Trainer into one for easy and robust configuration
In [6]:
def parse_args(args=None):
parser = ArgumentParser()
parser = pl.Trainer.add_argparse_args(parser)
parser = GLUEDataModule.add_argparse_args(parser)
parser = GLUETransformer.add_model_specific_args(parser)
parser.add_argument('--seed', type=int, default=42)
return parser.parse_args(args)
def main(args):
pl.seed_everything(args.seed)
dm = GLUEDataModule.from_argparse_args(args)
dm.prepare_data()
dm.setup('fit')
model = GLUETransformer(num_labels=dm.num_labels, eval_splits=dm.eval_splits, **vars(args))
trainer = pl.Trainer.from_argparse_args(args)
return dm, model, trainer
Training¶
CoLA¶
See an interactive view of the CoLA dataset in NLP Viewer
In [ ]:
mocked_args = """
--model_name_or_path albert-base-v2
--task_name cola
--max_epochs 3
--gpus 1""".split()
args = parse_args(mocked_args)
dm, model, trainer = main(args)
trainer.fit(model, dm)
MRPC¶
See an interactive view of the MRPC dataset in NLP Viewer
In [ ]:
mocked_args = """
--model_name_or_path distilbert-base-cased
--task_name mrpc
--max_epochs 3
--gpus 1""".split()
args = parse_args(mocked_args)
dm, model, trainer = main(args)
trainer.fit(model, dm)
MNLI¶
The MNLI dataset is huge, so we aren't going to bother trying to train it here.
Let's just make sure our multi-dataloader logic is right by skipping over training and going straight to validation.
See an interactive view of the MRPC dataset in NLP Viewer
In [ ]:
mocked_args = """
--model_name_or_path distilbert-base-uncased
--task_name mnli
--max_epochs 1
--gpus 1
--limit_train_batches 10
--progress_bar_refresh_rate 20""".split()
args = parse_args(mocked_args)
dm, model, trainer = main(args)
trainer.fit(model, dm)
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Great thanks from the entire Pytorch Lightning Team for your interest !¶
