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sglang/python/sglang/multimodal_gen/runtime/layers/lora/linear.py

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14 KiB
Python

# Copied and adapted from: https://github.com/hao-ai-lab/FastVideo
# SPDX-License-Identifier: Apache-2.0
# Code adapted from SGLang https://github.com/sgl-project/sglang/blob/main/python/sglang/srt/lora/layers.py
import torch
from torch import nn
from torch.distributed._composable.fsdp import (
CPUOffloadPolicy,
OffloadPolicy,
fully_shard,
)
from torch.distributed.tensor import DTensor
from sglang.multimodal_gen.runtime.distributed import (
get_local_torch_device,
get_tp_rank,
split_tensor_along_last_dim,
tensor_model_parallel_all_gather,
tensor_model_parallel_all_reduce,
)
from sglang.multimodal_gen.runtime.layers.linear import (
ColumnParallelLinear,
LinearBase,
MergedColumnParallelLinear,
QKVParallelLinear,
ReplicatedLinear,
RowParallelLinear,
)
from sglang.multimodal_gen.runtime.layers.vocab_parallel_embedding import (
VocabParallelEmbedding,
)
from sglang.multimodal_gen.utils import get_mixed_precision_state
torch._dynamo.config.recompile_limit = 16
class BaseLayerWithLoRA(nn.Module):
def __init__(
self,
base_layer: nn.Module,
lora_rank: int | None = None,
lora_alpha: int | None = None,
):
super().__init__()
self.base_layer: nn.Module = base_layer
self.merged: bool = False
self.cpu_weight = base_layer.weight.to("cpu")
# indicates adapter weights don't contain this layer
# (which shouldn't normally happen, but we want to separate it from the case of erroneous merging)
self.disable_lora: bool = False
self.lora_rank = lora_rank
self.lora_alpha = lora_alpha
self.lora_path: str | None = None
self.lora_A = None
self.lora_B = None
@torch.compile()
def forward(self, x: torch.Tensor) -> torch.Tensor:
lora_A = self.lora_A
lora_B = self.lora_B
if isinstance(self.lora_B, DTensor):
lora_B = self.lora_B.to_local()
lora_A = self.lora_A.to_local()
if not self.merged and not self.disable_lora:
lora_A_sliced = self.slice_lora_a_weights(lora_A.to(x, non_blocking=True))
lora_B_sliced = self.slice_lora_b_weights(lora_B.to(x, non_blocking=True))
delta = x @ lora_A_sliced.T @ lora_B_sliced.T
if self.lora_alpha != self.lora_rank:
delta = delta * (
self.lora_alpha / self.lora_rank # type: ignore
) # type: ignore
out, output_bias = self.base_layer(x)
return out + delta, output_bias
else:
out, output_bias = self.base_layer(x)
return out.to(x), output_bias
def slice_lora_a_weights(self, A: torch.Tensor) -> torch.Tensor:
return A
def slice_lora_b_weights(self, B: torch.Tensor) -> torch.Tensor:
return B
def set_lora_weights(
self,
A: torch.Tensor,
B: torch.Tensor,
lora_path: str | None = None,
) -> None:
self.lora_A = torch.nn.Parameter(
A
) # share storage with weights in the pipeline
self.lora_B = torch.nn.Parameter(B)
self.disable_lora = False
self.merge_lora_weights()
self.lora_path = lora_path
@torch.no_grad()
def merge_lora_weights(self) -> None:
if self.disable_lora:
return
if self.merged:
self.unmerge_lora_weights()
assert (
self.lora_A is not None and self.lora_B is not None
), "LoRA weights not set. Please set them first."
if isinstance(self.base_layer.weight, DTensor):
mesh = self.base_layer.weight.data.device_mesh
unsharded_base_layer = ReplicatedLinear(
input_size=self.base_layer.input_size,
output_size=self.base_layer.output_size,
bias=getattr(self.base_layer, "bias", None) is not None,
skip_bias_add=self.base_layer.skip_bias_add,
params_dtype=self.base_layer.params_dtype,
quant_config=self.base_layer.quant_config,
prefix=self.base_layer.prefix,
)
# Using offload param is on CPU, so current_device is for "CPU -> GPU -> merge -> CPU"
current_device = self.base_layer.weight.data.device
data = self.base_layer.weight.data.to(
get_local_torch_device()
).full_tensor()
data += self.slice_lora_b_weights(self.lora_B).to(
data
) @ self.slice_lora_a_weights(self.lora_A).to(data)
unsharded_base_layer.weight = nn.Parameter(data.to(current_device))
if isinstance(getattr(self.base_layer, "bias", None), DTensor):
unsharded_base_layer.bias = nn.Parameter(
self.base_layer.bias.to(get_local_torch_device(), non_blocking=True)
.full_tensor()
.to(current_device)
)
offload_policy = (
CPUOffloadPolicy() if "cpu" in str(current_device) else OffloadPolicy()
)
mp_policy = get_mixed_precision_state().mp_policy
self.base_layer = fully_shard(
unsharded_base_layer,
mesh=mesh,
mp_policy=mp_policy,
offload_policy=offload_policy,
)
else:
current_device = self.base_layer.weight.data.device
data = self.base_layer.weight.data.to(get_local_torch_device())
data += self.slice_lora_b_weights(
self.lora_B.to(data)
) @ self.slice_lora_a_weights(self.lora_A.to(data))
self.base_layer.weight.data = data.to(current_device, non_blocking=True)
self.merged = True
@torch.no_grad()
# @torch.compile(dynamic=True)
def unmerge_lora_weights(self) -> None:
if self.disable_lora:
return
if not self.merged:
raise ValueError(
"LoRA weights not merged. Please merge them first before unmerging."
)
# avoid precision loss
if isinstance(self.base_layer.weight, DTensor):
device = self.base_layer.weight.data.device
self.base_layer.weight = nn.Parameter(
self.cpu_weight.to(device, non_blocking=True)
)
else:
self.base_layer.weight.data = self.cpu_weight.data.to(
self.base_layer.weight, non_blocking=True
)
self.merged = False
class VocabParallelEmbeddingWithLoRA(BaseLayerWithLoRA):
"""
Vocab parallel embedding layer with support for LoRA (Low-Rank Adaptation).
Note: The current version does not yet implement the LoRA functionality.
This class behaves exactly the same as the base VocabParallelEmbedding.
Future versions will integrate LoRA functionality to support efficient parameter fine-tuning.
"""
def __init__(
self,
base_layer: VocabParallelEmbedding,
) -> None:
super().__init__(base_layer)
def forward(self, input_: torch.Tensor) -> torch.Tensor:
raise NotImplementedError(
"We don't support VocabParallelEmbeddingWithLoRA yet."
)
class ColumnParallelLinearWithLoRA(BaseLayerWithLoRA):
def __init__(
self,
base_layer: ColumnParallelLinear,
lora_rank: int | None = None,
lora_alpha: int | None = None,
) -> None:
super().__init__(base_layer, lora_rank, lora_alpha)
def forward(self, input_: torch.Tensor) -> torch.Tensor:
# duplicate the logic in ColumnParallelLinear
bias = self.base_layer.bias if not self.base_layer.skip_bias_add else None
output_parallel = self.base_layer.quant_method.apply(
self.base_layer, input_, bias
)
if self.base_layer.gather_output:
output = tensor_model_parallel_all_gather(output_parallel)
else:
output = output_parallel
output_bias = self.base_layer.bias if self.base_layer.skip_bias_add else None
return output, output_bias
def slice_lora_a_weights(self, A: torch.Tensor) -> torch.Tensor:
return A
def slice_lora_b_weights(self, B: torch.Tensor) -> torch.Tensor:
tp_rank = get_tp_rank()
shard_size = self.base_layer.output_partition_sizes[0]
start_idx = tp_rank * shard_size
end_idx = (tp_rank + 1) * shard_size
B = B[start_idx:end_idx, :]
return B
class MergedColumnParallelLinearWithLoRA(ColumnParallelLinearWithLoRA):
def __init__(
self,
base_layer: MergedColumnParallelLinear,
lora_rank: int | None = None,
lora_alpha: int | None = None,
) -> None:
super().__init__(base_layer, lora_rank, lora_alpha)
def slice_lora_a_weights(self, A: torch.Tensor) -> torch.Tensor:
return A.to(self.base_layer.weight)
def slice_lora_b_weights(self, B: torch.Tensor) -> torch.Tensor:
tp_rank = get_tp_rank()
# Since the outputs for both gate and up are identical, we use a random one.
shard_size = self.base_layer.output_partition_sizes[0]
start_idx = tp_rank * shard_size
end_idx = (tp_rank + 1) * shard_size
return B[:, start_idx:end_idx, :]
class QKVParallelLinearWithLoRA(ColumnParallelLinearWithLoRA):
def __init__(
self,
base_layer: QKVParallelLinear,
lora_rank: int | None = None,
lora_alpha: int | None = None,
) -> None:
super().__init__(base_layer, lora_rank, lora_alpha)
def slice_lora_a_weights(self, A: torch.Tensor) -> torch.Tensor:
return A
def slice_lora_b_weights(
self, B: list[torch.Tensor]
) -> tuple[torch.Tensor, torch.Tensor]:
tp_rank = get_tp_rank()
B_q, B_kv = B
base_layer = self.base_layer
q_proj_shard_size = base_layer.q_proj_shard_size
kv_proj_shard_size = base_layer.kv_proj_shard_size
num_kv_head_replicas = base_layer.num_kv_head_replicas
q_start_idx = q_proj_shard_size * tp_rank
q_end_idx = q_start_idx + q_proj_shard_size
kv_shard_id = tp_rank // num_kv_head_replicas
kv_start_idx = kv_proj_shard_size * kv_shard_id
kv_end_idx = kv_start_idx + kv_proj_shard_size
return B_q[q_start_idx:q_end_idx, :], B_kv[:, kv_start_idx:kv_end_idx, :]
class RowParallelLinearWithLoRA(BaseLayerWithLoRA):
def __init__(
self,
base_layer: RowParallelLinear,
lora_rank: int | None = None,
lora_alpha: int | None = None,
) -> None:
super().__init__(base_layer, lora_rank, lora_alpha)
def forward(self, input_: torch.Tensor):
# duplicate the logic in RowParallelLinear
if self.base_layer.input_is_parallel:
input_parallel = input_
else:
tp_rank = get_tp_rank()
splitted_input = split_tensor_along_last_dim(
input_, num_partitions=self.base_layer.tp_size
)
input_parallel = splitted_input[tp_rank].contiguous()
output_parallel = self.base_layer.quant_method.apply(
self.base_layer, input_parallel
)
if self.set_lora:
output_parallel = self.apply_lora(output_parallel, input_parallel)
if self.base_layer.reduce_results and self.base_layer.tp_size > 1:
output_ = tensor_model_parallel_all_reduce(output_parallel)
else:
output_ = output_parallel
if not self.base_layer.skip_bias_add:
output = (
output_ + self.base_layer.bias
if self.base_layer.bias is not None
else output_
)
output_bias = None
else:
output = output_
output_bias = self.base_layer.bias
return output, output_bias
def slice_lora_a_weights(self, A: torch.Tensor) -> torch.Tensor:
tp_rank = get_tp_rank()
shard_size = self.base_layer.input_size_per_partition
start_idx = tp_rank * shard_size
end_idx = (tp_rank + 1) * shard_size
A = A[:, start_idx:end_idx].contiguous()
return A
def slice_lora_b_weights(self, B: torch.Tensor) -> torch.Tensor:
return B
def get_lora_layer(
layer: nn.Module,
lora_rank: int | None = None,
lora_alpha: int | None = None,
) -> BaseLayerWithLoRA | None:
supported_layer_types: dict[type[LinearBase], type[BaseLayerWithLoRA]] = {
# the order matters
# VocabParallelEmbedding: VocabParallelEmbeddingWithLoRA,
QKVParallelLinear: QKVParallelLinearWithLoRA,
MergedColumnParallelLinear: MergedColumnParallelLinearWithLoRA,
ColumnParallelLinear: ColumnParallelLinearWithLoRA,
RowParallelLinear: RowParallelLinearWithLoRA,
ReplicatedLinear: BaseLayerWithLoRA,
}
for src_layer_type, lora_layer_type in supported_layer_types.items():
if isinstance(layer, src_layer_type): # pylint: disable=unidiomatic-typecheck
ret = lora_layer_type(
layer,
lora_rank=lora_rank,
lora_alpha=lora_alpha,
)
return ret
return None
# source: https://github.com/vllm-project/vllm/blob/93b38bea5dd03e1b140ca997dfaadef86f8f1855/vllm/lora/utils.py#L9
def replace_submodule(
model: nn.Module, module_name: str, new_module: nn.Module
) -> nn.Module:
"""Replace a submodule in a model with a new module."""
parent = model.get_submodule(".".join(module_name.split(".")[:-1]))
target_name = module_name.split(".")[-1]
setattr(parent, target_name, new_module)
return new_module