dpo.py

import os
from trl import DPOTrainer, DPOConfig
import torch
from accelerate import Accelerator
from utils import (
    ScriptArguments,
    DEFINE_PAD_TOKEN,
    create_peft,
    format_prompt,
    resolve_system_prompt,
)
from transformers import (
    AutoTokenizer,
    BitsAndBytesConfig,
    HfArgumentParser,
    AutoModelForCausalLM,
)
from data_adapter import load_preference_dataset

os.environ["WANDB_PROJECT"] = "ma-rlhf"
os.environ["WANDB_RUN_NAME"] = "dpo"

parser = HfArgumentParser(ScriptArguments)
train_args: ScriptArguments = parser.parse_args_into_dataclasses(return_remaining_strings=True)[0]

dataset_name = train_args.dataset_name
dataset_sub_name = train_args.dataset_sub_name
dataset_split = train_args.dataset_split
model_name = train_args.model_name
deepspeed_config_name = train_args.deepspeed_config_name
output_max_length = train_args.output_max_length
seq_length = train_args.seq_length
batch_size = train_args.batch_size
output_name = train_args.output_name
is_peft = train_args.use_QLora
is_use_flash_attention2 = train_args.use_flash_attention_2
num_train_epochs = train_args.num_train_epochs
beta = 0.1 # default
gradient_accumulation_steps = train_args.gradient_accumulation_steps
learning_rate = train_args.learning_rate
use_qlora_double_quant = train_args.use_qlora_double_quant
default_system_prompt = resolve_system_prompt(train_args.system_prompt)


def create_model_tokenizer(name):
    # QLoRA
    bnb_config = BitsAndBytesConfig(
        load_in_4bit=True, bnb_4bit_quant_type="nf4", bnb_4bit_compute_dtype=torch.bfloat16,
        bnb_4bit_use_double_quant=use_qlora_double_quant,
    )

    device_map = {"": Accelerator().local_process_index}
    print('device map: ', device_map)

    model = AutoModelForCausalLM.from_pretrained(
        model_name,
        quantization_config=bnb_config if is_peft else None,
        device_map=device_map,
        trust_remote_code=True,
        use_flash_attention_2=is_use_flash_attention2,
    )

    tokenizer = AutoTokenizer.from_pretrained(model_name, use_fast=True, model_max_length=seq_length,
        trust_remote_code=True,)

    tokenizer.add_special_tokens({'pad_token': DEFINE_PAD_TOKEN})
    model.pad_token_id = tokenizer.pad_token_id
    model.pad_token = tokenizer.pad_token


    return model, tokenizer


def create_dpo_datasets(datasets_name, dataset_sub_name, tokenizer):
    train_dataset = load_preference_dataset(
        datasets_name,
        dataset_sub_name=dataset_sub_name,
        split=dataset_split,
        default_system_prompt=default_system_prompt,
    )
    train_dataset = train_dataset.map(
        lambda example: {
            "prompt": format_prompt(example["prompt"], system_prompt=example["system"]),
            "chosen": example["chosen"],
            "rejected": example["rejected"],
        },
        remove_columns=["system"],
    )

    return train_dataset, None


def train():
    model, tokenizer = create_model_tokenizer(model_name)  # model is sequence classification
    train_datasets, test_datasets = create_dpo_datasets(
        dataset_name, None, tokenizer
    )

    # PEFT
    peft_config = create_peft(is_peft)

    training_args = DPOConfig(
        output_dir=output_name,
        save_strategy='epoch',
        logging_steps=1,
        num_train_epochs=num_train_epochs,
        gradient_checkpointing=True,
        bf16=True,
        learning_rate=learning_rate,
        warmup_ratio=0.05,
        per_device_train_batch_size=batch_size,
        per_device_eval_batch_size=batch_size,
        gradient_accumulation_steps=gradient_accumulation_steps,
        deepspeed=deepspeed_config_name,
        report_to='wandb',
        lr_scheduler_type='cosine',
        # max_steps=100,
        # loss_type: Literal[
        #     "sigmoid", "hinge", "ipo", "kto_pair", "bco_pair", "sppo_hard", "nca_pair", "robust"
        # ] = "sigmoid"
        loss_type='sigmoid', # standard dpo
        dataset_num_proc=64,
        max_completion_length=output_max_length,
        max_prompt_length= output_max_length,
        max_length=seq_length,
        )

    trainer = DPOTrainer(
        model,
        None,
        args=training_args,
        train_dataset=train_datasets,
        peft_config=peft_config,
        processing_class=tokenizer,
    )

    trainer.train()
    trainer.save_model(output_name)


if __name__ == "__main__":
    train()