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import torch
from einops import rearrange
from torch import Tensor
from comfy.ldm.modules.attention import optimized_attention
import comfy.model_management
def attention(q: Tensor, k: Tensor, v: Tensor, pe: Tensor) -> Tensor:
q, k = apply_rope(q, k, pe)
heads = q.shape[1]
x = optimized_attention(q, k, v, heads, skip_reshape=True)
return x
def rope(pos: Tensor, dim: int, theta: int) -> Tensor:
assert dim % 2 == 0
if comfy.model_management.is_device_mps(pos.device) or comfy.model_management.is_intel_xpu():
device = torch.device("cpu")
else:
device = pos.device
scale = torch.linspace(0, (dim - 2) / dim, steps=dim//2, dtype=torch.float64, device=device)
omega = 1.0 / (theta**scale)
out = torch.einsum("...n,d->...nd", pos.to(dtype=torch.float32, device=device), omega)
out = torch.stack([torch.cos(out), -torch.sin(out), torch.sin(out), torch.cos(out)], dim=-1)
out = rearrange(out, "b n d (i j) -> b n d i j", i=2, j=2)
return out.to(dtype=torch.float32, device=pos.device)
def apply_rope(xq: Tensor, xk: Tensor, freqs_cis: Tensor):
xq_ = xq.float().reshape(*xq.shape[:-1], -1, 1, 2)
xk_ = xk.float().reshape(*xk.shape[:-1], -1, 1, 2)
xq_out = freqs_cis[..., 0] * xq_[..., 0] + freqs_cis[..., 1] * xq_[..., 1]
xk_out = freqs_cis[..., 0] * xk_[..., 0] + freqs_cis[..., 1] * xk_[..., 1]
return xq_out.reshape(*xq.shape).type_as(xq), xk_out.reshape(*xk.shape).type_as(xk)
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