ColossalAI/colossalai/engine/ophooks/zero_hook.py

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import torch
from colossalai.registry import OPHOOKS
from colossalai.zero.shard_utils import BaseShardStrategy
from ._base_ophook import BaseOpHook
@OPHOOKS.register_module
class ZeroHook(BaseOpHook):
"""
A hook to process sharded param for ZeRO method.
"""
def __init__(self, shard_strategy: BaseShardStrategy):
super().__init__()
self.shard_strategy = shard_strategy
def pre_fwd_exec(self, module: torch.nn.Module, *args):
for param in module.parameters():
assert hasattr(param, 'col_attr')
self.shard_strategy.gather([param.col_attr.data])
param.data = param.col_attr.data.payload
def post_fwd_exec(self, module: torch.nn.Module, *args):
for param in module.parameters():
assert hasattr(param, 'col_attr')
self.shard_strategy.shard([param.col_attr.data])
param.data = torch.empty([], dtype=param.col_attr.data.dtype, device=param.col_attr.data.payload.device)
def pre_bwd_exec(self, module: torch.nn.Module, input, output):
for param in module.parameters():
assert hasattr(param, 'col_attr')
self.shard_strategy.gather([param.col_attr.data])
param.data = param.col_attr.data.payload
# Store local accumulated grad shard
if param.grad is not None:
if param.col_attr.bwd_count == 0:
# We haven't stored local accumulated grad yet
assert param.col_attr.grad is None
param.col_attr.grad = param.grad.data
param.grad = None
else:
# We have stored local accumulated grad
# The grad here must be locally computed full grad in this backward pass
assert param.grad.shape == param.col_attr.data.origin_shape
param.col_attr.bwd_count += 1
def post_bwd_exec(self, module: torch.nn.Module, input):
for param in module.parameters():
assert hasattr(param, 'col_attr')
self.shard_strategy.shard([param.col_attr.data])
param.data = torch.empty([], dtype=param.col_attr.data.dtype, device=param.col_attr.data.payload.device)
def pre_iter(self):
pass
def post_iter(self):
pass