[tensor] use communication autograd func (#1617)

* [tensor] use communication autograd func

* change all to all comm spec info

* rename pattern and distinguish fwd/bwd

* polish code
This commit is contained in:
YuliangLiu0306
2022-09-23 13:31:15 +08:00
committed by GitHub
parent c7ac0f4ab2
commit 702dbc5288
5 changed files with 348 additions and 109 deletions

View File

@@ -18,11 +18,225 @@ __all__ = [
]
def _all_gather(tensor, comm_spec):
'''
Implement all gather operation on device mesh based on information provided by comm_spec.
'''
process_groups_list = comm_spec.device_mesh.process_groups_dict[comm_spec.logical_process_axis]
for rank_list, process_group in process_groups_list:
if dist.get_rank() in rank_list:
tensor_list = [
torch.zeros(tensor.shape, dtype=tensor.dtype, device=tensor.device)
for _ in range(comm_spec.device_mesh.mesh_shape[comm_spec.logical_process_axis])
]
tensor = tensor
group = process_group
dist.all_gather(tensor_list, tensor, group=group)
output = torch.cat(tuple(tensor_list), comm_spec.gather_dim).contiguous()
return output
def _split(tensor, comm_spec):
'''
Implement shard operation on device mesh based on information provided by comm_spec.
'''
process_groups_list = comm_spec.device_mesh.process_groups_dict[comm_spec.logical_process_axis]
for rank_list, _ in process_groups_list:
if dist.get_rank() in rank_list:
tensor = tensor
dim = comm_spec.shard_dim
length = tensor.shape[comm_spec.shard_dim] // len(rank_list)
start = length * rank_list.index(dist.get_rank())
output = torch.narrow(tensor, dim, start, length)
return output
def _all_to_all(tensor, comm_spec):
'''
Implement all to all operation on device mesh based on information provided by comm_spec.
'''
process_groups_list = comm_spec.device_mesh.process_groups_dict[comm_spec.logical_process_axis]
for rank_list, process_group in process_groups_list:
if dist.get_rank() in rank_list:
new_shape = list(tensor.shape)
new_shape[comm_spec.shard_dim] = new_shape[comm_spec.shard_dim] // len(rank_list)
new_shape = torch.Size(new_shape)
output_tensor_list = [
torch.zeros(new_shape, dtype=tensor.dtype, device=tensor.device) for _ in range(len(rank_list))
]
dim = comm_spec.shard_dim
length = tensor.shape[comm_spec.shard_dim] // len(rank_list)
input_tensor_list = [
torch.narrow(tensor, dim, length * i, length).contiguous() for i in range(len(rank_list))
]
group = process_group
dist.all_to_all(output_tensor_list, input_tensor_list, group)
output = torch.cat(tuple(output_tensor_list), comm_spec.gather_dim).contiguous()
return output
def _all_reduce(tensor, comm_spec):
'''
Implement all reduce operation on device mesh based on information provided by comm_spec.
'''
process_groups_list = comm_spec.device_mesh.process_groups_dict[comm_spec.logical_process_axis]
for rank_list, process_group in process_groups_list:
if dist.get_rank() in rank_list:
dist.all_reduce(tensor, op=ReduceOp.SUM, group=process_group)
return tensor
class _ReduceGrad(torch.autograd.Function):
"""
A customized communication operation which forward is an identity operation,
backward is all_reduce operation.
Args:
input_: input matrix.
comm_spec: comm_spec will give information like process group, rank list, etc.
"""
@staticmethod
def symbolic(graph, input_):
return input_
@staticmethod
def forward(ctx, input_, comm_spec):
ctx.comm_spec = comm_spec
return input_
@staticmethod
def backward(ctx, grad_output):
return _all_reduce(grad_output, ctx.comm_spec), None
class _ReduceInput(torch.autograd.Function):
"""
A customized communication operation which forward is all_reduce operation,
backward is an identity operation.
Args:
input_: input matrix.
comm_spec: comm_spec will give information like process group, rank list, etc.
"""
@staticmethod
def symbolic(graph, input_):
return _all_reduce(input_)
@staticmethod
def forward(ctx, input_, comm_spec):
return _all_reduce(input_, comm_spec)
@staticmethod
def backward(ctx, grad_output):
return grad_output, None
class _SplitForwardGatherBackward(torch.autograd.Function):
"""
A customized communication operation which forward is split operation,
backward is an all gather operation.
Args:
input_: input matrix.
comm_spec: comm_spec will give information like process group, rank list, etc.
"""
@staticmethod
def symbolic(graph, input_):
return _split(input_)
@staticmethod
def forward(ctx, input_, comm_spec):
ctx.comm_spec = comm_spec
return _split(input_, comm_spec)
@staticmethod
def backward(ctx, grad_output):
return _all_gather(grad_output, ctx.comm_spec), None
class _GatherForwardSplitBackward(torch.autograd.Function):
"""
A customized communication operation which forward is an all gather operation,
backward is split operation.
Args:
input_: input matrix.
comm_spec: comm_spec will give information like process group, rank list, etc.
"""
@staticmethod
def symbolic(graph, input_):
return _all_gather(input_)
@staticmethod
def forward(ctx, input_, comm_spec):
ctx.comm_spec = comm_spec
return _all_gather(input_, comm_spec)
@staticmethod
def backward(ctx, grad_output):
return _split(grad_output, ctx.comm_spec), None
class _AllToAll(torch.autograd.Function):
"""
A customized communication operation which forward is an all to all operation,
backward is an all to all operation.
Args:
input_: input matrix.
comm_spec: comm_spec will give information like process group, rank list, etc.
"""
@staticmethod
def symbolic(graph, input_):
return _all_to_all(input_)
@staticmethod
def forward(ctx, input_, comm_spec):
output = _all_to_all(input_, comm_spec)
comm_spec_for_backward = CommSpec(comm_pattern=comm_spec.comm_pattern,
sharding_spec=comm_spec.sharding_spec,
gather_dim=comm_spec.shard_dim,
shard_dim=comm_spec.gather_dim,
logical_process_axis=comm_spec.logical_process_axis)
ctx.comm_spec = comm_spec_for_backward
return output
@staticmethod
def backward(ctx, grad_outputs):
return _all_to_all(grad_outputs, ctx.comm_spec), None
def reduce_grad(input_, comm_spec):
return _ReduceGrad.apply(input_, comm_spec)
def reduce_input(input_, comm_spec):
return _ReduceInput.apply(input_, comm_spec)
def split_forward_gather_backward(input_, comm_spec):
return _SplitForwardGatherBackward.apply(input_, comm_spec)
def gather_forward_split_backward(input_, comm_spec):
return _GatherForwardSplitBackward.apply(input_, comm_spec)
def all_to_all(input_, comm_spec):
return _AllToAll.apply(input_, comm_spec)
class CollectiveCommPattern(Enum):
ALLGATHER = 'all_gather'
ALLTOALL = 'all_to_all'
SHARD = 'shard'
ALLREDUCE = 'all_reduce'
GATHER_FWD_SPLIT_BWD = 'gather_fwd_split_bwd'
ALL2ALL_FWD_ALL2ALL_BWD = 'all2all_fwd_all2all_bwd'
SPLIT_FWD_GATHER_BWD = 'split_fwd_gather_bwd'
REDUCE_FWD_IDENTITY_BWD = 'all_reduce_fwd_identity_bwd'
IDENTITY_FWD_ALLREDUCE_BWD = 'identity_fwd_all_reduce_bwd'
class CommSpec:
@@ -42,12 +256,19 @@ class CommSpec:
logical_process_axis(Union(int, List[int]), Optional): The mesh_dim to implement the communication action.
'''
def __init__(self, comm_pattern, sharding_spec, gather_dim=None, shard_dim=None, logical_process_axis=None):
def __init__(self,
comm_pattern,
sharding_spec,
gather_dim=None,
shard_dim=None,
logical_process_axis=None,
forward_only=False):
self.comm_pattern = comm_pattern
self.sharding_spec = sharding_spec
self.gather_dim = gather_dim
self.shard_dim = shard_dim
self.logical_process_axis = logical_process_axis
self.forward_only = forward_only
if isinstance(self.logical_process_axis, list):
self.device_mesh = self.sharding_spec.device_mesh.flatten_device_mesh
self.logical_process_axis = 0
@@ -56,21 +277,24 @@ class CommSpec:
def __repr__(self):
res_list = ["CommSpec:("]
if self.comm_pattern == CollectiveCommPattern.ALLGATHER:
res_list.append(f"comm_pattern:all_gather, ")
if self.comm_pattern == CollectiveCommPattern.GATHER_FWD_SPLIT_BWD:
res_list.append(f"comm_pattern:GATHER_FWD_SPLIT_BWD, ")
res_list.append(f"gather_dim:{self.gather_dim}, ")
res_list.append(f"logical_process_axis:{self.logical_process_axis})")
elif self.comm_pattern == CollectiveCommPattern.ALLTOALL:
res_list.append(f"comm_pattern:all2all, ")
elif self.comm_pattern == CollectiveCommPattern.ALL2ALL_FWD_ALL2ALL_BWD:
res_list.append(f"comm_pattern:ALL2ALL_FWD_ALL2ALL_BWD, ")
res_list.append(f"gather_dim:{self.gather_dim}, ")
res_list.append(f"shard_dim:{self.shard_dim}, ")
res_list.append(f"logical_process_axis: {self.logical_process_axis})")
elif self.comm_pattern == CollectiveCommPattern.SHARD:
res_list.append(f"comm_pattern:shard, ")
elif self.comm_pattern == CollectiveCommPattern.SPLIT_FWD_GATHER_BWD:
res_list.append(f"comm_pattern:SPLIT_FWD_GATHER_BWD, ")
res_list.append(f"shard_dim:{self.shard_dim}, ")
res_list.append(f"logical_process_axis:{self.logical_process_axis})")
elif self.comm_pattern == CollectiveCommPattern.ALLREDUCE:
res_list.append(f"comm_pattern:all_reduce, ")
elif self.comm_pattern == CollectiveCommPattern.REDUCE_FWD_IDENTITY_BWD:
res_list.append(f"comm_pattern:REDUCE_FWD_IDENTITY_BWD, ")
res_list.append(f"logical_process_axis:{self.logical_process_axis})")
elif self.comm_pattern == CollectiveCommPattern.IDENTITY_FWD_ALLREDUCE_BWD:
res_list.append(f"comm_pattern:IDENTITY_FWD_ALLREDUCE_BWD, ")
res_list.append(f"logical_process_axis:{self.logical_process_axis})")
return ''.join(res_list)
@@ -82,16 +306,38 @@ class CommSpec:
For shard operation, it is an on-chip operation, so the communication cost is zero.
'''
comm_size = reduce(operator.mul, self.sharding_spec.get_sharded_shape_per_device(), 1)
if self.comm_pattern == CollectiveCommPattern.ALLGATHER:
return self.device_mesh.all_gather_cost(comm_size, self.logical_process_axis)
if self.comm_pattern == CollectiveCommPattern.ALLTOALL:
return self.device_mesh.all_to_all_cost(comm_size, self.logical_process_axis)
if self.comm_pattern == CollectiveCommPattern.ALLREDUCE:
return self.device_mesh.all_reduce_cost(comm_size, self.logical_process_axis)
if self.comm_pattern == CollectiveCommPattern.SHARD:
if self.comm_pattern == CollectiveCommPattern.GATHER_FWD_SPLIT_BWD:
forward_communication_cost = self.device_mesh.all_gather_cost(comm_size, self.logical_process_axis)
# give a tiny cost to shard
return 10
raise RuntimeError(f"Could not find a matching CollectiveCommPattern for {self.comm_pattern}.")
backward_communication_cost = 10
if self.comm_pattern == CollectiveCommPattern.ALL2ALL_FWD_ALL2ALL_BWD:
forward_communication_cost = self.device_mesh.all_to_all_cost(comm_size, self.logical_process_axis)
# grad should have same shape as input tensor
# all to all operation has same logical process axis as forward.
backward_communication_cost = self.device_mesh.all_to_all_cost(comm_size, self.logical_process_axis)
if self.comm_pattern == CollectiveCommPattern.REDUCE_FWD_IDENTITY_BWD:
forward_communication_cost = self.device_mesh.all_reduce_cost(comm_size, self.logical_process_axis)
backward_communication_cost = 0
if self.comm_pattern == CollectiveCommPattern.IDENTITY_FWD_ALLREDUCE_BWD:
forward_communication_cost = 0
backward_communication_cost = self.device_mesh.all_reduce_cost(comm_size, self.logical_process_axis)
if self.comm_pattern == CollectiveCommPattern.SPLIT_FWD_GATHER_BWD:
# give a tiny cost to shard
forward_communication_cost = 10
backward_communication_cost = self.device_mesh.all_gather_cost(comm_size, self.logical_process_axis)
try:
if self.forward_only:
total_communication_cost = forward_communication_cost
else:
total_communication_cost = forward_communication_cost + backward_communication_cost
except:
raise RuntimeError(f"Could not find a matching CollectiveCommPattern for {self.comm_pattern}.")
return total_communication_cost
def covert_spec_to_action(self, tensor):
'''
@@ -101,64 +347,21 @@ class CommSpec:
Argument:
tensor(torch.Tensor): Tensor stored in each device, which could be different in different ranks.
'''
process_groups_list = self.device_mesh.process_groups_dict[self.logical_process_axis]
if self.comm_pattern == CollectiveCommPattern.ALLGATHER:
for rank_list, process_group in process_groups_list:
if dist.get_rank() in rank_list:
tensor_list = [
torch.zeros(tensor.shape, dtype=tensor.dtype, device=tensor.device)
for _ in range(self.device_mesh.mesh_shape[self.logical_process_axis])
]
tensor = tensor
group = process_group
dist.all_gather(tensor_list, tensor, group=group)
tensor.data = torch.cat(tuple(tensor_list), self.gather_dim)
elif self.comm_pattern == CollectiveCommPattern.SHARD:
for rank_list, process_group in process_groups_list:
if dist.get_rank() in rank_list:
tensor = tensor
dim = self.shard_dim
length = tensor.shape[self.shard_dim] // len(rank_list)
start = length * rank_list.index(dist.get_rank())
tensor.data = torch.narrow(tensor, dim, start, length)
elif self.comm_pattern == CollectiveCommPattern.ALLTOALL:
for rank_list, process_group in process_groups_list:
if dist.get_rank() in rank_list:
new_shape = list(tensor.shape)
new_shape[self.shard_dim] = new_shape[self.shard_dim] // len(rank_list)
new_shape = torch.Size(new_shape)
output_tensor_list = [
torch.zeros(new_shape, dtype=tensor.dtype, device=tensor.device) for _ in range(len(rank_list))
]
dim = self.shard_dim
length = tensor.shape[self.shard_dim] // len(rank_list)
input_tensor_list = [
torch.narrow(tensor, dim, length * i, length).contiguous() for i in range(len(rank_list))
]
group = process_group
dist.all_to_all(output_tensor_list, input_tensor_list, group)
tensor.data = torch.cat(tuple(output_tensor_list), self.gather_dim)
elif self.comm_pattern == CollectiveCommPattern.ALLREDUCE:
# For the consistency of collective communication operation, we temporally do not
# allow all_reduce two different mesh dimensions in the same time.
# e.g.: MatMul[(R, S01), (S01, R)] -> Partial(R, R),
# all_reduce(Partial, logical_pg=(0, 1)) is NOT allowed, instead
# we need to do this in two steps:
# 1. all_reduce(Partial, logical_pg=1)
# 2. all_reduce(Partial, logical_pg=0)
for rank_list, process_group in process_groups_list:
if dist.get_rank() in rank_list:
dist.all_reduce(tensor, op=ReduceOp.SUM, group=process_group)
tensor.data = tensor
if self.comm_pattern in pattern_to_func_dict:
tensor.data = pattern_to_func_dict[self.comm_pattern](tensor, self)
else:
tensor.data = tensor
pattern_to_func_dict = {
CollectiveCommPattern.GATHER_FWD_SPLIT_BWD: gather_forward_split_backward,
CollectiveCommPattern.ALL2ALL_FWD_ALL2ALL_BWD: all_to_all,
CollectiveCommPattern.SPLIT_FWD_GATHER_BWD: split_forward_gather_backward,
CollectiveCommPattern.REDUCE_FWD_IDENTITY_BWD: reduce_input,
CollectiveCommPattern.IDENTITY_FWD_ALLREDUCE_BWD: reduce_grad,
}
@dataclass
class ShapeConsistencyOptions:
"""
@@ -180,6 +383,7 @@ class ShapeConsistencyManager(metaclass=SingletonMeta):
def __init__(self):
self._options = None
self._forward_only = False
self.total_communication_cost = 0
self.total_transform_steps = 0
self.cached_spec_pairs_transform_path = {}
@@ -193,6 +397,15 @@ class ShapeConsistencyManager(metaclass=SingletonMeta):
assert isinstance(options_, ShapeConsistencyOptions)
self._options = options_
@property
def forward_only(self):
return self._forward_only
@forward_only.setter
def forward_only(self, value):
assert isinstance(value, bool)
self._forward_only = value
def get_all_all_gather_spec(self, source_spec, orig_cost):
'''
Get all valid sharding specs from source_spec with single all-gather operation, and
@@ -224,7 +437,7 @@ class ShapeConsistencyManager(metaclass=SingletonMeta):
device_mesh_shape: (4, 4): 0}
'''
valid_spec_dict = {}
comm_pattern = CollectiveCommPattern.ALLGATHER
comm_pattern = CollectiveCommPattern.GATHER_FWD_SPLIT_BWD
for target_pair in source_spec.dim_partition_dict.items():
shard_list = all_gather_simulator(target_pair)
index = target_pair[0]
@@ -240,10 +453,14 @@ class ShapeConsistencyManager(metaclass=SingletonMeta):
# generate the CommSpec to record the action of source_sharding_spec->new_sharding_spec
gather_dim = index
logical_process_axis = target_pair[1][-1]
comm_spec = CommSpec(comm_pattern,
sharding_spec=source_spec,
gather_dim=gather_dim,
logical_process_axis=logical_process_axis)
comm_spec = CommSpec(
comm_pattern,
sharding_spec=source_spec,
gather_dim=gather_dim,
# shard_dim will be used during backward
shard_dim=gather_dim,
logical_process_axis=logical_process_axis,
forward_only=self.forward_only)
# compute the communication cost with CommSpec
cost = comm_spec.get_comm_cost()
@@ -288,7 +505,7 @@ class ShapeConsistencyManager(metaclass=SingletonMeta):
device_mesh_shape: (4, 4): 0}
'''
valid_spec_dict = {}
comm_pattern = CollectiveCommPattern.ALLTOALL
comm_pattern = CollectiveCommPattern.ALL2ALL_FWD_ALL2ALL_BWD
tensor_dims = len(source_spec.entire_shape)
for f_index in range(tensor_dims - 1):
for b_index in range(f_index + 1, tensor_dims):
@@ -331,7 +548,8 @@ class ShapeConsistencyManager(metaclass=SingletonMeta):
sharding_spec=source_spec,
gather_dim=gather_dim,
shard_dim=shard_dim,
logical_process_axis=logical_process_axis)
logical_process_axis=logical_process_axis,
forward_only=self.forward_only)
# compute the communication cost with CommSpec
cost = comm_spec.get_comm_cost()
@@ -388,7 +606,7 @@ class ShapeConsistencyManager(metaclass=SingletonMeta):
device_mesh_shape: (4, 4): 0}
'''
valid_spec_dict = {}
comm_pattern = CollectiveCommPattern.SHARD
comm_pattern = CollectiveCommPattern.SPLIT_FWD_GATHER_BWD
# legal sharding dims means the mesh_id is still available to use.
legal_sharding_dims = [i for i in range(len(source_spec.device_mesh.mesh_shape))]
@@ -415,8 +633,10 @@ class ShapeConsistencyManager(metaclass=SingletonMeta):
logical_process_axis = shard_list[-1]
comm_spec = CommSpec(comm_pattern,
sharding_spec=source_spec,
gather_dim=shard_dim,
shard_dim=shard_dim,
logical_process_axis=logical_process_axis)
logical_process_axis=logical_process_axis,
forward_only=self.forward_only)
# compute the communication cost with CommSpec
cost = comm_spec.get_comm_cost()