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PeterGriffinJin
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# Copyright 2024 Bytedance Ltd. and/or its affiliates
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from .base import BasePPOCritic
from .dp_critic import DataParallelPPOCritic
__all__ = ["BasePPOCritic", "DataParallelPPOCritic"]

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# Copyright 2024 Bytedance Ltd. and/or its affiliates
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
Base class for a critic
"""
from abc import ABC, abstractmethod
import torch
from verl import DataProto
__all__ = ['BasePPOCritic']
class BasePPOCritic(ABC):
def __init__(self, config):
super().__init__()
self.config = config
@abstractmethod
def compute_values(self, data: DataProto) -> torch.Tensor:
"""Compute values"""
pass
@abstractmethod
def update_critic(self, data: DataProto):
"""Update the critic"""
pass

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# Copyright 2024 Bytedance Ltd. and/or its affiliates
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
Implement a multiprocess PPOCritic
"""
import itertools
from typing import Iterable
import torch
import torch.distributed
from torch import nn, optim
from torch.distributed.fsdp import FullyShardedDataParallel as FSDP
from verl import DataProto
from verl.trainer.ppo import core_algos
from verl.workers.critic import BasePPOCritic
from verl.utils.py_functional import append_to_dict
from verl.utils.torch_functional import masked_mean
from verl.utils.ulysses import ulysses_pad_and_slice_inputs, gather_outpus_and_unpad
from verl.utils.seqlen_balancing import rearrange_micro_batches, get_reverse_idx
from flash_attn.bert_padding import pad_input, unpad_input, rearrange, index_first_axis
__all__ = ['DataParallelPPOCritic']
class DataParallelPPOCritic(BasePPOCritic):
def __init__(self, config, critic_module: nn.Module, critic_optimizer: optim.Optimizer):
super().__init__(config=config)
self.critic_module = critic_module
self.critic_optimizer = critic_optimizer
self.use_remove_padding = self.config.model.get('use_remove_padding', False)
print(f'Critic use_remove_padding={self.use_remove_padding}')
assert self.config.ppo_mini_batch_size % self.config.ppo_micro_batch_size == 0
self.gradient_accumulation = self.config.ppo_mini_batch_size // self.config.ppo_micro_batch_size
self.ulysses_sequence_parallel_size = self.config.get('ulysses_sequence_parallel_size', 1)
def _forward_micro_batch(self, micro_batch):
response_length = micro_batch['responses'].size(-1)
with torch.autocast(device_type='cuda', dtype=torch.bfloat16):
input_ids = micro_batch['input_ids']
batch, seqlen = input_ids.shape
attention_mask = micro_batch['attention_mask']
position_ids = micro_batch['position_ids']
if self.use_remove_padding:
input_ids_rmpad, indices, *_ = unpad_input(input_ids.unsqueeze(-1),
attention_mask) # input_ids_rmpad (total_nnz, ...)
input_ids_rmpad = input_ids_rmpad.transpose(0, 1) # (1, total_nnz)
# unpad the position_ids to align the rotary
position_ids_rmpad = index_first_axis(rearrange(position_ids.unsqueeze(-1), "b s ... -> (b s) ..."),
indices).transpose(0, 1)
# pad and slice the inputs if sp > 1
if self.ulysses_sequence_parallel_size > 1:
input_ids_rmpad, position_ids_rmpad, pad_size = ulysses_pad_and_slice_inputs(input_ids_rmpad, \
position_ids_rmpad, \
sp_size=self.ulysses_sequence_parallel_size)
# only pass input_ids and position_ids to enable flash_attn_varlen
output = self.critic_module(input_ids=input_ids_rmpad,
attention_mask=None,
position_ids=position_ids_rmpad,
use_cache=False) # prevent model thinks we are generating
values_rmpad = output.logits
values_rmpad = values_rmpad.squeeze(0) # (total_nnz)
# gather output if sp > 1
if self.ulysses_sequence_parallel_size > 1:
values_rmpad = gather_outpus_and_unpad(values_rmpad,
gather_dim=0,
unpad_dim=0,
padding_size=pad_size)
# pad it back
values = pad_input(values_rmpad, indices=indices, batch=batch, seqlen=seqlen).squeeze(-1)
values = values[:, -response_length - 1:-1]
else:
output = self.critic_module(input_ids=input_ids,
attention_mask=attention_mask,
position_ids=position_ids,
use_cache=False) # prevent model thinks we are generating
values = output.logits
values = values[:, -response_length - 1:-1].squeeze(-1)
return values
def _optimizer_step(self):
assert self.config.grad_clip is not None
if isinstance(self.critic_module, FSDP):
grad_norm = self.critic_module.clip_grad_norm_(self.config.grad_clip)
else:
grad_norm = torch.nn.utils.clip_grad_norm_(self.critic_module.parameters(), max_norm=self.config.grad_clip)
self.critic_optimizer.step()
return grad_norm
def compute_values(self, data: DataProto) -> torch.Tensor:
self.critic_module.eval()
micro_batch_size = data.meta_info['micro_batch_size']
select_keys = ['responses', 'input_ids', 'attention_mask', 'position_ids']
batch = data.select(batch_keys=select_keys).batch
use_dynamic_bsz = data.meta_info['use_dynamic_bsz']
if use_dynamic_bsz:
# split using dynamic bsz
max_token_len = data.meta_info['max_token_len'] * self.ulysses_sequence_parallel_size
micro_batches, indices = rearrange_micro_batches(batch=batch, max_token_len=max_token_len)
else:
micro_batches = batch.split(micro_batch_size)
values_lst = []
for micro_batch in micro_batches:
with torch.no_grad():
values = self._forward_micro_batch(micro_batch)
values_lst.append(values)
values = torch.concat(values_lst, dim=0)
responses = data.batch['responses']
attention_mask = data.batch['attention_mask']
response_length = responses.size(1)
values = values * attention_mask[:, -response_length - 1:-1]
if use_dynamic_bsz:
indices = list(itertools.chain.from_iterable(indices))
assert len(indices) == values.size(0), f"{len(indices)} vs. {values.size()}"
revert_indices = torch.tensor(get_reverse_idx(indices), dtype=torch.long)
values = values[revert_indices]
return values
def update_critic(self, data: DataProto):
# make sure we are in training mode
self.critic_module.train()
metrics = {}
select_keys = ['input_ids', 'responses', 'attention_mask', 'position_ids', 'values', 'returns']
batch = data.select(batch_keys=select_keys).batch
# Split to make minibatch iterator for updating the actor
# See PPO paper for details. https://arxiv.org/abs/1707.06347
dataloader = batch.split(self.config.ppo_mini_batch_size)
for batch_idx, data in enumerate(dataloader):
# split batch into micro_batches
mini_batch = data
if self.config.use_dynamic_bsz:
max_token_len = self.config.ppo_max_token_len_per_gpu * self.ulysses_sequence_parallel_size
micro_batches, _ = rearrange_micro_batches(batch=mini_batch, max_token_len=max_token_len)
else:
micro_batches = mini_batch.split(self.config.ppo_micro_batch_size)
self.critic_optimizer.zero_grad()
for data in micro_batches:
data = data.cuda() # critic device is cpu when using offload
input_ids = data['input_ids']
responses = data['responses']
attention_mask = data['attention_mask']
position_ids = data['position_ids']
values = data['values']
returns = data['returns']
response_length = responses.size(1)
eos_mask = attention_mask[:, -response_length - 1:-1]
vpreds = self._forward_micro_batch(data)
# assert not torch.any(torch.isnan(vpreds)).item()
vf_loss, vf_clipfrac = core_algos.compute_value_loss(vpreds=vpreds,
values=values,
returns=returns,
eos_mask=eos_mask,
cliprange_value=self.config.cliprange_value)
loss = vf_loss / self.gradient_accumulation
loss.backward()
data = {
'critic/vf_loss': vf_loss.detach().item(),
'critic/vf_clipfrac': vf_clipfrac.detach().item(),
'critic/vpred_mean': masked_mean(vpreds, eos_mask).detach().item(),
}
append_to_dict(metrics, data)
grad_norm = self._optimizer_step()
data = {'critic/grad_norm': grad_norm.detach().item()}
append_to_dict(metrics, data)
self.critic_optimizer.zero_grad()
return metrics

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# Copyright 2024 Bytedance Ltd. and/or its affiliates
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
Implement a multiprocess PPOCritic
"""
from functools import partial
from typing import Iterable
import torch
import torch.distributed
from omegaconf import OmegaConf
from torch import nn
from verl import DataProto
from verl.trainer.ppo import core_algos
from verl.workers.critic import BasePPOCritic
from verl.utils.megatron.pipeline_parallel import (compute_transformers_input_shapes, make_batch_generator)
from verl.utils.py_functional import append_to_dict
from verl.utils.torch_dtypes import PrecisionType
from verl.utils.torch_functional import masked_mean, broadcast_dict_tensor, split_dict_tensor_into_batches
from verl.utils.megatron import sequence_parallel as sp_utils
from verl.utils.megatron.optimizer_config import OptimizerConfig
from megatron.optimizer import DistributedOptimizer
from megatron.core import parallel_state as mpu
from megatron.core.pipeline_parallel import get_forward_backward_func
class MegatronPPOCritic(BasePPOCritic):
def __init__(self, config, model_config, megatron_config, critic_module: nn.ModuleList,
critic_optimizer: DistributedOptimizer, critic_optimizer_config: OptimizerConfig):
super().__init__(config=config)
self.model_config = model_config
self.megatron_config = megatron_config
self.critic_module = critic_module
self.critic_optimizer = critic_optimizer
self.critic_optimizer_config = critic_optimizer_config
# we create a separate nametuple for optimizer step so that global args won't affect it.
self.optimizer_step_args = OmegaConf.create({
'skip_grad': None,
'overlap_dp_param_comm': False,
'overlap_dp_grad_comm': False,
'gradient_accumulation_steps': 1,
'sequence_parallel': self.megatron_config.sequence_parallel,
'DDP_impl': 'local',
'layernorm_allreduce_bucket_threshold': 0,
'pipeline_model_parallel_split_rank': None,
'reduce_grads_use_alltoall': False
})
if self.config.kl_ctrl.type == 'fixed':
self.kl_ctrl = core_algos.FixedKLController(kl_coef=self.config.kl_ctrl.kl_coef)
elif self.config.kl_ctrl.type == 'adaptive':
assert self.config.kl_ctrl.horizon > 0, f'horizon must be larger than 0. Got {self.config.kl_ctrl.horizon}'
self.kl_ctrl = core_algos.AdaptiveKLController(init_kl_coef=self.config.kl_ctrl.kl_coef,
target_kl=self.config.kl_ctrl.target_kl,
horizon=self.config.kl_ctrl.horizon)
else:
raise NotImplementedError
def compute_values(self, data: DataProto) -> DataProto:
# data.batch = data.batch.to(self.critic_module.module.device)
responses = data.batch['responses']
attention_mask = data.batch['attention_mask']
response_length = responses.size(1)
with torch.no_grad():
output = self.forward_backward_batch(data=data, forward_only=True)
if mpu.is_pipeline_last_stage(ignore_virtual=True):
# only on last rank. It should be on every tp rank
values = torch.cat([o['vpreds'] for o in output], dim=0) # (bs, seq_size, vocal_size)
values = values.to(torch.float32)
else:
values = torch.empty_like(attention_mask, dtype=torch.float32)
# each tp ranks should contain the same value
values = values * attention_mask
values = values[:, -response_length - 1:-1]
values = values.contiguous()
# sync among pp ranks
torch.distributed.broadcast(tensor=values,
src=mpu.get_pipeline_model_parallel_last_rank(),
group=mpu.get_pipeline_model_parallel_group())
# add empty cache after each compute
torch.cuda.empty_cache()
return values
def make_minibatch_iterator(self, data: DataProto) -> Iterable[DataProto]:
select_keys = ['input_ids', 'responses', 'attention_mask', 'position_ids', 'values', 'returns']
data = data.select(batch_keys=select_keys)
return data.make_iterator(mini_batch_size=self.config.ppo_mini_batch_size,
epochs=self.config.ppo_epochs,
dataloader_kwargs={'shuffle': self.config.shuffle})
def forward_backward_batch(self, data: DataProto, forward_only=False):
# broadcast from last pp rank to all other pp ranks
data.batch = data.batch.contiguous()
broadcast_dict_tensor(data.batch,
src=mpu.get_pipeline_model_parallel_last_rank(),
group=mpu.get_pipeline_model_parallel_group())
# split into micro-batches
data.batch['attention_mask'] = data.batch['attention_mask'].to(bool)
batches = split_dict_tensor_into_batches(data.batch, batch_size=self.config.ppo_micro_batch_size)
n_micro_batch = len(batches)
seq_len = batches[0]['input_ids'].shape[1]
# compute input shapes for pp stages
input_shapes = compute_transformers_input_shapes(
batches,
meta_info={
'sequence_parallel': self.megatron_config.sequence_parallel,
'hidden_size': self.model_config.hidden_size
})
forward_backward_func = get_forward_backward_func()
def loss_func(output, data, meta_info):
if forward_only:
return 1.0, {'vpreds': output.logits}
responses = data['responses']
attention_mask = data['attention_mask']
values = data['values']
returns = data['returns']
response_length = responses.size(1)
eos_mask = attention_mask[:, -response_length:]
cliprange_value = self.config.cliprange_value
vpreds = output.logits # (bs, sequence_length)
vpreds = vpreds[:, -response_length - 1:-1]
vf_loss, vf_clipfrac = core_algos.compute_value_loss(vpreds=vpreds,
values=values,
returns=returns,
eos_mask=eos_mask,
cliprange_value=cliprange_value)
stats = {
'critic/vf_loss': vf_loss.detach().item(),
'critic/vf_clipfrac': vf_clipfrac.detach().item(),
'critic/vpred_mean': masked_mean(vpreds, eos_mask).detach().item(),
}
return vf_loss, stats
def forward_step(batch_iter, model):
batch = next(batch_iter)
input_ids = batch['input_ids']
attention_mask = batch['attention_mask']
position_ids = batch['position_ids']
output = model(input_ids=input_ids, attention_mask=attention_mask, position_ids=position_ids)
return output, partial(loss_func, data=batch, meta_info={})
# batch should be a list of batches inside micro-batches
batch_generator = make_batch_generator(batches, vpp_size=len(self.critic_module))
# TODO: we may use the new schedule instead
# for flash-attn: (seq_len, batch_size, hidden_size) = (mbs*seq_len, 1, hidden_size)
if mpu.get_pipeline_model_parallel_world_size() > 1:
losses_reduced = forward_backward_func(
forward_step_func=forward_step,
data_iterator=batch_generator,
model=self.critic_module,
num_microbatches=n_micro_batch,
input_shapes=input_shapes, # must set for flash-attn sequence packing
seq_length=self.config.ppo_micro_batch_size * seq_len, # no use when input_shapes was set
hidden_size=self.model_config.hidden_size, # no use when input_shapes was set
micro_batch_size=1, # no use when input_shapes was set
forward_only=forward_only,
)
else:
losses_reduced = forward_backward_func(
forward_step_func=forward_step,
data_iterator=batch_generator,
model=self.critic_module,
num_microbatches=n_micro_batch,
seq_length=self.config.ppo_micro_batch_size * seq_len, # in use for pp = 1
hidden_size=self.model_config.hidden_size, # in use for pp = 1
micro_batch_size=1, # in use for pp = 1
forward_only=forward_only,
)
# loss_reduces contains the stats returned from loss_func
return losses_reduced
def update_critic(self, dataloader: Iterable[DataProto]):
metrics = {}
for data in dataloader:
# data = data.batch.to(self.critic_module.device)
self.critic_optimizer.zero_grad()
# use use_contiguous_buffers_in_local_ddp and no overlap_dp_param_comm
for chunk in self.critic_module:
chunk.zero_grad_buffer(zero_buffer=(not self.critic_optimizer_config.use_distributed_optimizer))
metric_micro_batch = self.forward_backward_batch(data)
update_successful, grad_norm, num_zeros_in_grad = self.critic_optimizer.step(
self.megatron_config, self.megatron_config.timers)
if update_successful:
# allgather already execute in optimizer.step in new megatron
pass
else:
raise NotImplementedError
for metric in metric_micro_batch:
append_to_dict(metrics, metric) # append the metric from this micro-batch to global metrics.
# add empty cache after each compute
torch.cuda.empty_cache()
return metrics