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2026-07-13 12:47:19 +08:00

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4.9 KiB
Python

# Copyright Lightning AI. Licensed under the Apache License 2.0, see LICENSE file.
import lightning as L
import torch
from litgpt import LLM
from litgpt.data import Alpaca2k
class LitLLM(L.LightningModule):
def __init__(self, checkpoint_dir, tokenizer_dir=None, trainer_ckpt_path=None):
super().__init__()
self.llm = LLM.load(checkpoint_dir, tokenizer_dir=tokenizer_dir, distribute=None)
self.trainer_ckpt_path = trainer_ckpt_path
def setup(self, stage):
self.llm.trainer_setup(trainer_ckpt=self.trainer_ckpt_path)
def training_step(self, batch):
logits, loss = self.llm(input_ids=batch["input_ids"], target_ids=batch["labels"])
self.log("train_loss", loss, prog_bar=True)
return loss
def validation_step(self, batch):
logits, loss = self.llm(input_ids=batch["input_ids"], target_ids=batch["labels"])
self.log("validation_loss", loss, prog_bar=True)
return loss
def configure_optimizers(self):
warmup_steps = 10
optimizer = torch.optim.AdamW(self.llm.model.parameters(), lr=0.0002, weight_decay=0.0, betas=(0.9, 0.95))
scheduler = torch.optim.lr_scheduler.LambdaLR(optimizer, lambda step: step / warmup_steps)
return [optimizer], [scheduler]
if __name__ == "__main__":
batch_size = 8
accumulate_grad_batches = 1
#########################################################
# Use case 1: Pretraining from random weights
#########################################################
llm = LLM.load("EleutherAI/pythia-160m", tokenizer_dir="EleutherAI/pythia-160m", init="random")
llm.save("pythia-160m-random-weights")
del llm
lit_model = LitLLM(checkpoint_dir="pythia-160m-random-weights", tokenizer_dir="EleutherAI/pythia-160m")
data = Alpaca2k()
data.connect(lit_model.llm.tokenizer, batch_size=batch_size, max_seq_length=512)
trainer = L.Trainer(
devices=1,
accelerator="cuda",
max_epochs=1,
accumulate_grad_batches=accumulate_grad_batches,
precision="bf16-true",
)
trainer.fit(lit_model, data)
lit_model.llm.model.to(lit_model.llm.preprocessor.device)
lit_model.llm.generate("hello world")
del lit_model
#############################################################################
# Use case 2: Continued pretraining / finetuning from downloaded checkpoint
#############################################################################
lit_model = LitLLM(checkpoint_dir="EleutherAI/pythia-160m")
data = Alpaca2k()
data.connect(lit_model.llm.tokenizer, batch_size=batch_size, max_seq_length=512)
trainer = L.Trainer(
devices=1,
accelerator="cuda",
max_epochs=1,
accumulate_grad_batches=accumulate_grad_batches,
precision="bf16-true",
)
trainer.fit(lit_model, data)
lit_model.llm.model.to(lit_model.llm.preprocessor.device)
lit_model.llm.generate("hello world")
del lit_model
#########################################################
# Use case 3: Resume training from Trainer checkpoint
#########################################################
import os
def find_latest_checkpoint(directory):
latest_checkpoint = None
latest_time = 0
for root, _, files in os.walk(directory):
for file in files:
if file.endswith(".ckpt"):
file_path = os.path.join(root, file)
file_time = os.path.getmtime(file_path)
if file_time > latest_time:
latest_time = file_time
latest_checkpoint = file_path
return latest_checkpoint
lit_model = LitLLM(
checkpoint_dir="EleutherAI/pythia-160m", trainer_ckpt_path=find_latest_checkpoint("lightning_logs")
)
data.connect(lit_model.llm.tokenizer, batch_size=batch_size, max_seq_length=512)
trainer = L.Trainer(
devices=1,
accelerator="cuda",
max_epochs=1,
accumulate_grad_batches=accumulate_grad_batches,
precision="bf16-true",
)
trainer.fit(lit_model, data)
lit_model.llm.model.to(lit_model.llm.preprocessor.device)
lit_model.llm.generate("hello world")
#################################################################
# Use case 4: Resume training after saving a checkpoint manually
#################################################################
lit_model.llm.save("finetuned_checkpoint")
del lit_model
lit_model = LitLLM(checkpoint_dir="finetuned_checkpoint")
data.connect(lit_model.llm.tokenizer, batch_size=batch_size, max_seq_length=512)
trainer = L.Trainer(
devices=1,
accelerator="cuda",
max_epochs=1,
accumulate_grad_batches=accumulate_grad_batches,
precision="bf16-true",
)
trainer.fit(lit_model, data)
lit_model.llm.model.to(lit_model.llm.preprocessor.device)
lit_model.llm.generate("hello world")