from typing import Any, Callable, Dict, List, Optional, Union import torch import torch.nn as nn from coati.experience_maker import Experience, NaiveExperienceMaker from coati.models.base import Actor, Critic, get_base_model from coati.models.loss import GPTLMLoss, PolicyLoss, ValueLoss from coati.models.utils import calc_action_log_probs from coati.replay_buffer import NaiveReplayBuffer from torch import Tensor from torch.optim import Optimizer from torch.utils.data import DistributedSampler from tqdm import tqdm from transformers.tokenization_utils_base import PreTrainedTokenizerBase from colossalai.utils import get_current_device from .base import Trainer from .callbacks import Callback from .strategies import Strategy from .utils import is_rank_0, to_device class PPOTrainer(Trainer): """ Trainer for PPO algorithm. Args: strategy (Strategy): the strategy to use for training actor (Actor): the actor model in ppo algorithm critic (Critic): the critic model in ppo algorithm reward_model (nn.Module): the reward model in rlhf algorithm to make reward of sentences initial_model (Actor): the initial model in rlhf algorithm to generate reference logics to limit the update of actor actor_optim (Optimizer): the optimizer to use for actor model critic_optim (Optimizer): the optimizer to use for critic model kl_coef (float, defaults to 0.1): the coefficient of kl divergence loss train_batch_size (int, defaults to 8): the batch size to use for training buffer_limit (int, defaults to 0): the max_size limitation of replay buffer buffer_cpu_offload (bool, defaults to True): whether to offload replay buffer to cpu eps_clip (float, defaults to 0.2): the clip coefficient of policy loss vf_coef (float, defaults to 1.0): the coefficient of value loss ptx_coef (float, defaults to 0.9): the coefficient of ptx loss value_clip (float, defaults to 0.4): the clip coefficient of value loss max_epochs (int, defaults to 1): the number of epochs of training process sample_replay_buffer (bool, defaults to False): whether to sample from replay buffer dataloader_pin_memory (bool, defaults to True): whether to pin memory for data loader offload_inference_models (bool, defaults to True): whether to offload inference models to cpu during training process callbacks (List[Callback], defaults to []): the callbacks to call during training process generate_kwargs (dict, optional): the kwargs to use while model generating """ def __init__(self, strategy: Strategy, actor: Actor, critic: Critic, reward_model: nn.Module, initial_model: Actor, actor_optim: Optimizer, critic_optim: Optimizer, kl_coef: float = 0.1, ptx_coef: float = 0.9, train_batch_size: int = 8, buffer_limit: int = 0, buffer_cpu_offload: bool = True, eps_clip: float = 0.2, vf_coef: float = 1.0, value_clip: float = 0.4, max_epochs: int = 1, sample_replay_buffer: bool = False, dataloader_pin_memory: bool = True, offload_inference_models: bool = True, callbacks: List[Callback] = [], **generate_kwargs) -> None: experience_maker = NaiveExperienceMaker(actor, critic, reward_model, initial_model, kl_coef) replay_buffer = NaiveReplayBuffer(train_batch_size, buffer_limit, buffer_cpu_offload) generate_kwargs = _set_default_generate_kwargs(strategy, generate_kwargs, actor) super().__init__(strategy, max_epochs, dataloader_pin_memory, callbacks, **generate_kwargs) self.experience_maker = experience_maker self.replay_buffer = replay_buffer self.sample_replay_buffer = sample_replay_buffer self.offload_inference_models = offload_inference_models self.actor = actor self.critic = critic self.actor_loss_fn = PolicyLoss(eps_clip) self.critic_loss_fn = ValueLoss(value_clip) self.vf_coef = vf_coef self.ptx_loss_fn = GPTLMLoss() self.ptx_coef = ptx_coef self.actor_optim = actor_optim self.critic_optim = critic_optim self.device = get_current_device() def _make_experience(self, inputs: Union[Tensor, Dict[str, Tensor]]) -> Experience: if isinstance(inputs, Tensor): return self.experience_maker.make_experience(inputs, **self.generate_kwargs) elif isinstance(inputs, dict): return self.experience_maker.make_experience(**inputs, **self.generate_kwargs) else: raise ValueError(f'Unsupported input type "{type(inputs)}"') def _learn(self): # replay buffer may be empty at first, we should rebuild at each training if not self.sample_replay_buffer: dataloader = self.strategy.setup_dataloader(self.replay_buffer, self.dataloader_pin_memory) if self.sample_replay_buffer: pbar = tqdm(range(self.max_epochs), desc='Train epoch', disable=not is_rank_0()) for _ in pbar: experience = self.replay_buffer.sample() experience.to_device(self.device) metrics = self.training_step(experience) pbar.set_postfix(metrics) else: for epoch in range(self.max_epochs): self._on_learn_epoch_start(epoch) if isinstance(dataloader.sampler, DistributedSampler): dataloader.sampler.set_epoch(epoch) pbar = tqdm(dataloader, desc=f'Train epoch [{epoch+1}/{self.max_epochs}]', disable=not is_rank_0()) for experience in pbar: self._on_learn_batch_start() experience.to_device(self.device) metrics = self.training_step(experience) self._on_learn_batch_end(metrics, experience) pbar.set_postfix(metrics) self._on_learn_epoch_end(epoch) def fit(self, prompt_dataloader, pretrain_dataloader, num_episodes: int = 50000, max_timesteps: int = 500, update_timesteps: int = 5000) -> None: time = 0 self.pretrain_dataloader = pretrain_dataloader self.prompt_dataloader = prompt_dataloader self._on_fit_start() for episode in range(num_episodes): self._on_episode_start(episode) for timestep in tqdm(range(max_timesteps), desc=f'Episode [{episode+1}/{num_episodes}]', disable=not is_rank_0()): time += 1 prompts = next(iter(self.prompt_dataloader)) self._on_make_experience_start() if self.offload_inference_models: # TODO(ver217): this may be controlled by strategy if they are prepared by strategy self.experience_maker.initial_model.to(self.device) self.experience_maker.reward_model.to(self.device) experience = self._make_experience(prompts) self._on_make_experience_end(experience) self.replay_buffer.append(experience) if time % update_timesteps == 0: if self.offload_inference_models: self.experience_maker.initial_model.to('cpu') self.experience_maker.reward_model.to('cpu') self._learn() self.replay_buffer.clear() self._on_episode_end(episode) self._on_fit_end() def training_step(self, experience: Experience) -> Dict[str, float]: self.actor.train() self.critic.train() # policy loss num_actions = experience.action_mask.size(1) actor_output = self.actor(experience.sequences, attention_mask=experience.attention_mask) action_log_probs = calc_action_log_probs(actor_output, experience.sequences, num_actions) actor_loss = self.actor_loss_fn(action_log_probs, experience.action_log_probs, experience.advantages, action_mask=experience.action_mask) # ptx loss if self.ptx_coef != 0: batch = next(iter(self.pretrain_dataloader)) batch = to_device(batch, self.device) ptx_log_probs = self.actor(batch['input_ids'], attention_mask=batch['attention_mask'])['logits'] ptx_loss = self.ptx_loss_fn(ptx_log_probs, batch['labels']) actor_loss = ptx_loss * self.ptx_coef + actor_loss * (1 - self.ptx_coef) self.strategy.backward(actor_loss, self.actor, self.actor_optim) self.strategy.optimizer_step(self.actor_optim) self.actor_optim.zero_grad() # value loss values = self.critic(experience.sequences, action_mask=experience.action_mask, attention_mask=experience.attention_mask) critic_loss = self.critic_loss_fn(values, experience.values, experience.reward, action_mask=experience.action_mask) critic_loss = critic_loss * self.vf_coef self.strategy.backward(critic_loss, self.critic, self.critic_optim) self.strategy.optimizer_step(self.critic_optim) self.critic_optim.zero_grad() return {'reward': experience.reward.mean().item()} def _set_default_generate_kwargs(strategy: Strategy, generate_kwargs: dict, actor: Actor) -> Dict: unwrapper_model = strategy.unwrap_model(actor) hf_model = get_base_model(unwrapper_model) new_kwargs = {**generate_kwargs} # use huggingface models method directly if 'prepare_inputs_fn' not in generate_kwargs and hasattr(hf_model, 'prepare_inputs_for_generation'): new_kwargs['prepare_inputs_fn'] = hf_model.prepare_inputs_for_generation if 'update_model_kwargs_fn' not in generate_kwargs and hasattr(hf_model, '_update_model_kwargs_for_generation'): new_kwargs['update_model_kwargs_fn'] = hf_model._update_model_kwargs_for_generation return new_kwargs