ColossalAI/applications/Chat/coati/trainer/ppo.py

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from typing import Dict, List
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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
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from coati.replay_buffer import NaiveReplayBuffer
from torch import Tensor
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from torch.optim import Optimizer
from torch.utils.data import DataLoader, DistributedSampler
from tqdm import tqdm
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from colossalai.utils import get_current_device
from .base import OnPolicyTrainer
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from .callbacks import Callback
from .strategies import ColossalAIStrategy, Strategy
from .utils import is_rank_0, to_device
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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
class PPOTrainer(OnPolicyTrainer):
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"""
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
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initial_model (Actor): the initial model in rlhf algorithm to generate reference logics to limit the update of actor
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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 buffer
buffer_cpu_offload (bool, defaults to True): whether to offload buffer to cpu
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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
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value_clip (float, defaults to 0.4): the clip coefficient of value loss
sample_buffer (bool, defaults to False): whether to sample from buffer
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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
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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,
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value_clip: float = 0.4,
sample_buffer: bool = False,
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dataloader_pin_memory: bool = True,
offload_inference_models: bool = True,
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callbacks: List[Callback] = [],
**generate_kwargs
) -> None:
if isinstance(strategy, ColossalAIStrategy):
from colossalai.booster.plugin import GeminiPlugin
assert not (isinstance(strategy.plugin, GeminiPlugin) and offload_inference_models), \
"GeminiPlugin is not compatible with manual model.to('cpu')"
buffer = NaiveReplayBuffer(train_batch_size, buffer_limit, buffer_cpu_offload)
super().__init__(
strategy, buffer,
sample_buffer, dataloader_pin_memory,
callbacks
)
self.generate_kwargs = _set_default_generate_kwargs(strategy, generate_kwargs, actor)
self.experience_maker = NaiveExperienceMaker(actor, critic, reward_model, initial_model, kl_coef)
self.offload_inference_models = offload_inference_models
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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()
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self.ptx_coef = ptx_coef
self.actor_optim = actor_optim
self.critic_optim = critic_optim
self.device = get_current_device()
def _make_experience(self, collect_step: int) -> Experience:
prompts = self.prompt_dataloader.next()
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)
if isinstance(prompts, Tensor):
return self.experience_maker.make_experience(prompts, **self.generate_kwargs)
elif isinstance(prompts, dict):
return self.experience_maker.make_experience(**prompts, **self.generate_kwargs)
else:
raise ValueError(f'Unsupported input type "{type(prompts)}"')
def _training_step(self, experience: Experience) -> Dict[str, float]:
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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)
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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 = self.pretrain_dataloader.next()
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'])
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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
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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 _learn(self, update_step: int):
if self.offload_inference_models:
self.experience_maker.initial_model.to('cpu')
self.experience_maker.reward_model.to('cpu')
# buffer may be empty at first, we should rebuild at each training
if self.sample_buffer:
experience = self.buffer.sample()
self._on_learn_batch_start()
experience.to_device(self.device)
metrics = self._training_step(experience)
self._on_learn_batch_end(metrics, experience)
else:
if isinstance(self.dataloader.sampler, DistributedSampler):
self.dataloader.sampler.set_epoch(update_step)
pbar = tqdm(
self.dataloader,
desc=f'Train epoch [{update_step + 1}]',
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)