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2026-07-13 12:40:42 +08:00

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Python

# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
#
# 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 __future__ import annotations
import random
from typing import TYPE_CHECKING, Any, TypedDict
import numpy as np
import paddle
from paddle import framework
from paddle.autograd import PyLayer
from paddle.framework import core
from ..meta_parallel.parallel_layers.random import get_rng_state_tracker
from ..meta_parallel.pp_utils import utils
from .recompute import (
check_recompute_necessary,
custom_state_manager,
detach_variable,
switch_rng_state_tracker,
)
if TYPE_CHECKING:
from collections.abc import Callable
from typing_extensions import NotRequired
from paddle.distributed.communication.group import Group
from paddle.nn import Layer
class _Ctx(TypedDict):
mp_group: Group
offload: NotRequired[bool]
partition: NotRequired[bool]
__all__ = []
def _split_activation(tensor, mp_group):
mp_degree = mp_group.nranks
mp_rank = mp_group.rank
if mp_degree < 2:
return tensor
tensor_numel = paddle.numel(tensor)
assert tensor_numel != 0, "can't recompute zero element"
assert tensor_numel % mp_degree == 0, (
f"The capacity of the activation ({tensor_numel}) cannot be divisible by mp_degree({mp_degree})"
)
# use inplace operation to save memory
data = tensor.flatten_()
part_size = tensor_numel // mp_degree
start = part_size * mp_rank
end = start + part_size
return data[start:end]
def _merge_activation(tensor, mp_group):
mp_degree = mp_group.nranks
mp_rank = mp_group.rank
if mp_degree < 2:
return tensor
# adapt to new dygraph
tensor_shape = list(tensor.shape)
tensor_shape[0] *= mp_group.nranks
out = paddle.empty(tensor_shape, tensor.dtype)
task = mp_group.process_group.all_gather(tensor.cuda(), out)
task.wait()
return out
class _HPRecomputeFunction(PyLayer):
"""
Compared with paddle.distributed.fleet.utils.recompute, there are the following differences:
1. In order to support PipeLineParallel, the input of recompute is modified to ensure that the input can be tuple type.
2. Offload support for activation
3. Support MP segmentation of activation to further reduce cuda memory
4. Adapt to the random state of MP
"""
@staticmethod
def forward(
ctx,
run_function,
all_outputs,
mp_group,
offload,
partition,
custom_get_state_func,
custom_set_state_func,
*args,
**kwargs,
):
# store for recomputing
ctx.run_function = run_function
ctx.kwargs = kwargs
# store the rng states
ctx.fwd_rng_state = paddle.get_rng_state()
ctx.fwd_rng_state_tracker = get_rng_state_tracker().get_states_tracker()
ctx.fwd_numpy_state = np.random.get_state()
ctx.fwd_random_state = random.getstate()
ctx.fwd_custom_state = custom_get_state_func()
ctx.custom_get_state_func = custom_get_state_func
ctx.custom_set_state_func = custom_set_state_func
# save config info
ctx.mp_group = mp_group
ctx.offload = offload
ctx.partition = partition
# save input for backward
ctx.inputs = []
ctx.tensor_indices = []
ctx.tensor_shapes = []
tensor_inputs = []
cur_device = paddle.get_device()
assert (
'gpu:' in paddle.get_device()
or 'xpu:' in paddle.get_device()
or cur_device.split(':')[0]
in paddle.device.get_all_custom_device_type()
), f"Recompute with RNG is not support current device: {cur_device}."
# TODO support AMP
tracer = framework._dygraph_tracer()
ctx.is_fw_autocast = (
False if tracer._amp_level == core.AmpLevel.O0 else True
)
if tracer._amp_level == core.AmpLevel.O2:
ctx.amp_level = 'O2'
elif tracer._amp_level in (core.AmpLevel.O1, core.AmpLevel.O0):
ctx.amp_level = 'O1'
else:
raise ValueError(f"unsupported amp level: {tracer._amp_level}")
ctx.amp_dtype = tracer._amp_dtype
ctx.amp_white_list, ctx.amp_black_list = tracer._get_amp_op_list()
with paddle.no_grad():
outputs = run_function(*args, **kwargs)
for i, arg in enumerate(args):
if paddle.is_tensor(arg):
state = arg.stop_gradient
if partition:
ctx.tensor_shapes.append(arg.shape)
partition = _split_activation(
arg.detach(), mp_group
).clone()
# TODO(shenliang03) not use calculate stream to D2H to speed
arg = partition.cpu() if offload else partition
else:
arg = arg.cpu() if offload else arg
arg.stop_gradient = state
tensor_inputs.append(arg)
ctx.tensor_indices.append(i)
ctx.inputs.append(None)
# In new dygraph mode, in some cases a subset of outputs is identity to the subset of inputs,
# which is inplace operating. When the inputs' stop_gradient is True, an
# error will occurs because the stop_gradient=True and inplace-op are not
# supported in the same time. The solution is to mark the inputs non_differentiable
# if its stop_gradient is True.
# Note:
# If not marked non_differentiable, all output tensors' attr `stop gradient`
# will be reset to `False` in c++ backend.
# See https://github.com/PaddlePaddle/Paddle/blob/9d62efb0e6e5373823039d9eda96cd5905426c0a/paddle/fluid/pybind/eager_py_layer.cc#L388
if framework.in_dynamic_mode() and state:
ctx.mark_non_differentiable(arg)
else:
ctx.inputs.append(arg)
ctx.save_for_backward(*tensor_inputs)
if paddle.is_tensor(outputs):
all_outputs += [outputs]
return outputs
else:
all_outputs += outputs
return tuple(outputs)
@staticmethod
def backward(ctx, *args):
with paddle.base.dygraph.guard():
# Restore inputs
inputs = list(ctx.inputs)
tensor_indices = ctx.tensor_indices
tensor_shapes = ctx.tensor_shapes
tensors = list(ctx.saved_tensor())
device_id = paddle.distributed.ParallelEnv().device_id
for i, idx in enumerate(tensor_indices):
if ctx.partition:
state = tensors[i].stop_gradient
tensors[i] = (
_merge_activation(tensors[i], ctx.mp_group)
.detach()
.reshape_(tensor_shapes[i])
)
tensors[i].stop_gradient = state
inputs[idx] = (
tensors[i].cuda(device_id) if ctx.offload else tensors[i]
)
tracer = framework._dygraph_tracer()
tracer._has_grad = True
# need restore auto_cast state as well as w/b list
with switch_rng_state_tracker(
ctx.fwd_rng_state,
ctx.fwd_rng_state_tracker,
ctx.fwd_numpy_state,
ctx.fwd_random_state,
ctx.fwd_custom_state,
ctx.custom_get_state_func,
ctx.custom_set_state_func,
):
if ctx.is_fw_autocast:
with paddle.amp.auto_cast(
enable=ctx.is_fw_autocast,
custom_white_list=ctx.amp_white_list,
custom_black_list=ctx.amp_black_list,
level=ctx.amp_level,
dtype=ctx.amp_dtype,
):
detached_inputs = detach_variable(tuple(inputs))
outputs = ctx.run_function(
*detached_inputs, **ctx.kwargs
)
else:
detached_inputs = detach_variable(tuple(inputs))
outputs = ctx.run_function(*detached_inputs, **ctx.kwargs)
if isinstance(outputs, core.eager.Tensor):
outputs = (outputs,)
assert len(outputs) == len(args)
forward_outputs_with_grad = []
backward_inputs = []
for i in range(len(outputs)):
if (
isinstance(outputs[i], core.eager.Tensor)
and not outputs[i].stop_gradient
):
forward_outputs_with_grad.append(outputs[i])
backward_inputs.append(args[i])
if len(forward_outputs_with_grad) == 0:
raise RuntimeError(
"none of output has stop_gradient=False, this recompute() is not necessary"
)
# actually backward
paddle.autograd.backward(forward_outputs_with_grad, backward_inputs)
grads = tuple(
inp._grad_ivar()
for inp in detached_inputs
if isinstance(inp, core.eager.Tensor)
)
return grads
def recompute_hybrid(
ctx: _Ctx, function: Layer | Callable[..., Any], *args: Any, **kwargs: Any
) -> Any:
"""
recompute intermediate activations to save the memory in hybrid parallel scene.
# NOTE(shenliang03)The current hybrid parallel recompute has limitations.
# It cannot handle the following situations:
# 1. The calculation output of recompute, there are tensors that do not require gradients.
# 2. The forward output tensor has no gradient. This problem can be solved temporarily by detach().
# 3. Here, we only use float dtype to distinguish whether a gradient is needed in output tensor
Parameters:
ctx(dict): include 'mp_group', 'offload', and 'partition' keys. the key 'mp_group' (Group), represents the activations are splitted
in which group. the key 'offload' (bool, optional, default=False), represents whether to offload to cpu. the key 'partition' (bool, optional, default=False),
represents whether to split activations in the mp_group.
function(paddle.nn.Layer): layer of sequence of layers that describes part of forward pass of the model
whose intermediate activations will be released to save memory in forward stage and will be recomputed
in backward stage for gradient calculation.
*args(Tensor): inputs(tuple) to the function.
**kwargs(Dict): inputs(dict) to the function.
Returns:
Output of function on args and kwargs.
"""
mp_group = ctx.get('mp_group', None)
assert mp_group is not None, (
"ctx must contains mp_group and mp_group can not be None."
)
offload = ctx.get('offload', False)
partition = ctx.get('partition', False)
if framework._dygraph_tracer()._has_grad:
check_recompute_necessary(args)
if custom_state_manager.custom_get_state_func is None:
assert custom_state_manager.custom_set_state_func is None
custom_get_state_func = lambda x=None: None
custom_set_state_func = lambda x=None: None
else:
custom_get_state_func = custom_state_manager.custom_get_state_func
custom_set_state_func = custom_state_manager.custom_set_state_func
all_outputs = []
_HPRecomputeFunction.apply(
function,
all_outputs,
mp_group,
offload,
partition,
custom_get_state_func,
custom_set_state_func,
*args,
**kwargs,
)
if len(all_outputs) == 1:
return all_outputs[0]
else:
for output in all_outputs:
if paddle.is_tensor(output) and not utils.is_float_tensor(output):
output.stop_gradient = True
return tuple(all_outputs)