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vllm-omni/vllm_omni/diffusion/layers/norm.py
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Python

from importlib.util import find_spec
import torch
import torch.nn as nn
import torch.nn.functional as F
from vllm.logger import init_logger
from vllm_omni.diffusion.layers.custom_op import CustomOp
logger = init_logger(__name__)
_HAS_MINDIESD = find_spec("mindiesd") is not None
class LayerNorm(nn.LayerNorm, CustomOp):
"""
LayerNorm implementation that inherits from both ``nn.LayerNorm`` and ``CustomOp``.
NPU:
Uses ``mindiesd.fast_layernorm(self, x)`` when MindIE-SD is installed.
CUDA / HIP / XPU / native:
Falls back to FP32 nn.LayerNorm implementation.
"""
def __init__(self, dim: int, eps: float = 1e-6, elementwise_affine: bool = True):
super().__init__(normalized_shape=dim, eps=eps, elementwise_affine=elementwise_affine)
# CustomOp.__init__ cannot be called here because it would re-run
# nn.Module initialization and clear LayerNorm parameters.
self._forward_method = CustomOp.dispatch_forward(self)
def forward(self, x: torch.Tensor) -> torch.Tensor:
return self._forward_method(x)
def forward_cuda(self, x: torch.Tensor) -> torch.Tensor:
return self.forward_native(x)
def forward_hip(self, x: torch.Tensor) -> torch.Tensor:
return self.forward_native(x)
def forward_xpu(self, x: torch.Tensor) -> torch.Tensor:
return self.forward_native(x)
def forward_npu(self, x: torch.Tensor) -> torch.Tensor:
if _HAS_MINDIESD:
try:
from mindiesd import fast_layernorm
return fast_layernorm(self, x)
except ImportError as e:
logger.warning_once(
"mindiesd.fast_layernorm import failed, falling back to FP32 layer_norm: %s",
e,
)
return self.forward_native(x)
def forward_native(self, x: torch.Tensor) -> torch.Tensor:
origin_dtype = x.dtype
return F.layer_norm(
x.float(),
self.normalized_shape,
self.weight.float() if self.weight is not None else None,
self.bias.float() if self.bias is not None else None,
self.eps,
).to(origin_dtype)
class RMSNorm(CustomOp):
def __init__(self, hidden_size: int, eps: float = 1e-6, dtype: torch.dtype = torch.float32) -> None:
super().__init__()
self.weight = nn.Parameter(torch.ones(hidden_size, dtype=dtype))
self.hidden_size = hidden_size
self.variance_epsilon = eps
def _forward_fused(self, x: torch.Tensor) -> torch.Tensor:
from vllm._custom_ops import rms_norm as fused_rms_norm
orig_shape = x.shape
hidden_size = orig_shape[-1]
x_2d = x.reshape(-1, hidden_size)
out = torch.empty_like(x_2d)
fused_rms_norm(out, x_2d, self.weight.data, self.variance_epsilon)
return out.reshape(orig_shape)
def forward_cuda(
self,
x: torch.Tensor,
) -> torch.Tensor:
# During torch.compile tracing, fused_rms_norm writes to `out` in-place
# (returns None) and accesses self.weight.data, which is a DTensor under
# HSDP. Both patterns confuse inductor's compute_ancestors scheduler.
# Fall back to forward_native so inductor can fuse the pure-PyTorch ops
# itself.
if torch.compiler.is_compiling():
return self.forward_native(x)
try:
return self._forward_fused(x)
except Exception:
return self.forward_native(x)
def forward_hip(
self,
x: torch.Tensor,
) -> torch.Tensor:
if torch.compiler.is_compiling():
return self.forward_native(x)
try:
return self._forward_fused(x)
except Exception:
return self.forward_native(x)
def forward_musa(
self,
x: torch.Tensor,
) -> torch.Tensor:
# Preserve the aten::rms_norm graph so dynamic Inductor can fuse the
# H3 Q/K norm with its inline RoPE path on MUSA.
return F.rms_norm(
x,
(self.hidden_size,),
self.weight,
self.variance_epsilon,
)
def forward_npu(
self,
x: torch.Tensor,
) -> torch.Tensor:
import torch_npu
output = torch_npu.npu_rms_norm(x, gamma=self.weight, epsilon=self.variance_epsilon)[0]
return output
def forward_xpu(
self,
x: torch.Tensor,
) -> torch.Tensor:
return self.forward_native(x)
def forward_native(
self,
x: torch.Tensor,
) -> torch.Tensor:
input_dtype = x.dtype
x = x.to(torch.float32)
variance = x.pow(2).mean(-1, keepdim=True)
out = x * torch.rsqrt(variance + self.variance_epsilon)
out = self.weight.to(torch.float32) * out
return out.to(input_dtype)
class RMSNormVAE(CustomOp):
"""Root Mean Square Layer Normalization for Channel-First or Last"""
def __init__(
self,
dim: int,
channel_first: bool = True,
images: bool = True,
bias: bool = False,
epsilon: float = 1e-6,
) -> None:
super().__init__()
broadcastable_dims = (1, 1, 1) if not images else (1, 1)
shape = (dim, *broadcastable_dims) if channel_first else (dim,)
self.channel_first = channel_first
self.scale = dim**0.5
self.gamma = nn.Parameter(torch.ones(shape))
self.bias = nn.Parameter(torch.zeros(shape)) if bias else None
self.epsilon = epsilon
self.gamma_rmsnorm = None
def forward_cuda(
self,
x: torch.Tensor,
) -> torch.Tensor:
return self.forward_native(x)
def forward_hip(
self,
x: torch.Tensor,
) -> torch.Tensor:
return self.forward_native(x)
def forward_npu(
self,
x: torch.Tensor,
) -> torch.Tensor:
import torch_npu
if self.gamma_rmsnorm is None:
self.gamma_rmsnorm = self.gamma.reshape(-1)
if self.channel_first:
x = x.transpose(1, -1)
out = torch_npu.npu_rms_norm(x, self.gamma_rmsnorm, epsilon=self.epsilon)[0].transpose(1, -1)
else:
out = torch_npu.npu_rms_norm(x, self.gamma_rmsnorm, epsilon=self.epsilon)[0]
if self.bias is not None:
out = out + self.bias
return out
def forward_xpu(
self,
x: torch.Tensor,
) -> torch.Tensor:
return self.forward_native(x)
def forward_native(
self,
x: torch.Tensor,
) -> torch.Tensor:
out = (
F.normalize(
x,
dim=(1 if self.channel_first else -1),
eps=self.epsilon,
)
* self.scale
* self.gamma
)
if self.bias is not None:
out = out + self.bias
return out