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Fix: Remove hardcoded CUDA autocast in Kandinsky 5 to fix import warning #12814

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Fix: Remove hardcoded CUDA autocast in Kandinsky 5 to fix import warning #12814

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Fix: Remove hardcoded CUDA autocast in Kandinsky 5 to fix import warning
adi776borate Dec 9, 2025
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github-actions[bot] Dec 11, 2025
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8 changes: 5 additions & 3 deletions src/diffusers/models/transformers/transformer_kandinsky.py
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Original file line number Diff line number Diff line change
Expand Up @@ -165,10 +165,12 @@ def __init__(self, model_dim, time_dim, max_period=10000.0):
self.activation = nn.SiLU()
self.out_layer = nn.Linear(time_dim, time_dim, bias=True)

@torch.autocast(device_type="cuda", dtype=torch.float32)
def forward(self, time):
args = torch.outer(time, self.freqs.to(device=time.device))
time = time.to(dtype=torch.float32)
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@yiyixuxu yiyixuxu Dec 11, 2025

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Suggested change
time = time.to(dtype=torch.float32)
origintal_dtype = time.dtype
time = time.to(dtype=torch.float32)

freqs = self.freqs.to(device=time.device, dtype=torch.float32)
args = torch.outer(time, freqs)
time_embed = torch.cat([torch.cos(args), torch.sin(args)], dim=-1)
time_embed = time_embed.to(dtype=self.in_layer.weight.dtype)
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@yiyixuxu yiyixuxu Dec 11, 2025

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Suggested change
time_embed = time_embed.to(dtype=self.in_layer.weight.dtype)
time_embed = time_embed.to(dtype=original_dtype)

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@adi776borate adi776borate Dec 11, 2025

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The reason I cast to self.in_layer.weight.dtype instead of original_dtype is to prevent runtime crashes on backends like XPU as mentioned by @vladmandic here.
If users load the pipeline in float16, and we pass time_embed as float32, that will raise an error, won't it?
I might be wrong, correct me if so.

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@adi776borate adi776borate Dec 13, 2025

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Hi! I also tried to apply your suggested change and ran the exact same code attached in the PR description above on an L40S (which supports bf16), and faced below error:

Traceback (most recent call last):
  File "/teamspace/studios/this_studio/diffusers/verify_fix.py", line 25, in <module>
    output = pipe(
             ^^^^^
  File "/home/zeus/miniconda3/envs/cloudspace/lib/python3.12/site-packages/torch/utils/_contextlib.py", line 120, in decorate_context
    return func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/teamspace/studios/this_studio/diffusers/src/diffusers/pipelines/kandinsky5/pipeline_kandinsky_t2i.py", line 731, in __call__
    pred_velocity = self.transformer(
                    ^^^^^^^^^^^^^^^^^
  File "/home/zeus/miniconda3/envs/cloudspace/lib/python3.12/site-packages/torch/nn/modules/module.py", line 1773, in _wrapped_call_impl
    return self._call_impl(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/zeus/miniconda3/envs/cloudspace/lib/python3.12/site-packages/torch/nn/modules/module.py", line 1784, in _call_impl
    return forward_call(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/teamspace/studios/this_studio/diffusers/src/diffusers/models/transformers/transformer_kandinsky.py", line 647, in forward
    text_embed = text_transformer_block(text_embed, time_embed, text_rope)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/zeus/miniconda3/envs/cloudspace/lib/python3.12/site-packages/torch/nn/modules/module.py", line 1773, in _wrapped_call_impl
    return self._call_impl(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/zeus/miniconda3/envs/cloudspace/lib/python3.12/site-packages/torch/nn/modules/module.py", line 1784, in _call_impl
    return forward_call(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/teamspace/studios/this_studio/diffusers/src/diffusers/models/transformers/transformer_kandinsky.py", line 461, in forward
    self_attn_params, ff_params = torch.chunk(self.text_modulation(time_embed).unsqueeze(dim=1), 2, dim=-1)
                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/zeus/miniconda3/envs/cloudspace/lib/python3.12/site-packages/torch/nn/modules/module.py", line 1773, in _wrapped_call_impl
    return self._call_impl(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/zeus/miniconda3/envs/cloudspace/lib/python3.12/site-packages/torch/nn/modules/module.py", line 1784, in _call_impl
    return forward_call(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/teamspace/studios/this_studio/diffusers/src/diffusers/models/transformers/transformer_kandinsky.py", line 280, in forward
    return self.out_layer(self.activation(x))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/zeus/miniconda3/envs/cloudspace/lib/python3.12/site-packages/torch/nn/modules/module.py", line 1773, in _wrapped_call_impl
    return self._call_impl(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/zeus/miniconda3/envs/cloudspace/lib/python3.12/site-packages/torch/nn/modules/module.py", line 1784, in _call_impl
    return forward_call(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/zeus/miniconda3/envs/cloudspace/lib/python3.12/site-packages/torch/nn/modules/linear.py", line 125, in forward
    return F.linear(input, self.weight, self.bias)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeError: mat1 and mat2 must have the same dtype, but got Float and BFloat16

Thus, I think casting to self.in_layer.weight.dtype is a safer option.
Please let me know your thoughts.

time_embed = self.out_layer(self.activation(self.in_layer(time_embed)))
return time_embed

Expand Down Expand Up @@ -269,8 +271,8 @@ def __init__(self, time_dim, model_dim, num_params):
self.out_layer.weight.data.zero_()
self.out_layer.bias.data.zero_()

@torch.autocast(device_type="cuda", dtype=torch.float32)
def forward(self, x):
x = x.to(dtype=self.out_layer.weight.dtype)
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umm actually this did not look correct to me - we want to upcast it to float32, no?

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@adi776borate adi776borate Dec 11, 2025

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Similarly, if we force x to float32 here, we might hit the same mismatch crash if the out_layer weights are float16/bfloat16.

return self.out_layer(self.activation(x))


Expand Down