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Fix MusicGen SDPA #31208

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Jun 14, 2024
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18 changes: 18 additions & 0 deletions src/transformers/models/musicgen/modeling_musicgen.py
Original file line number Diff line number Diff line change
Expand Up @@ -572,6 +572,24 @@ def forward(
output_attentions=output_attentions,
)

# Ignore copy
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This ignore copy doesn't work, any ideas why @ydshieh ?

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@ydshieh ydshieh Jun 3, 2024

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Hi. Copy and ignore copy only works with a named entity (like function, method, class). It could not be used in a place (block) where no declared name is given. Either refactor the code or just remove the copy statement

Copied from transformers.models.bart.modeling_bart.BartSdpaAttention with Bart->Musicgen

if no code re-factorization is possible.

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Thanks @ydshieh, I'll remove the copy statement

if (
attention_mask is not None
and (attention_mask.mean(dim=[1, 2, 3]) <= torch.finfo(attention_mask.dtype).min).any()
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What's the reason for using finfo here and not just 0?

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The attention has already been processed and is filled with -inf of the correspondant dtype!

):
logger.warning_once(
'`torch.nn.functional.scaled_dot_product_attention` does not support having an empty attention mask. Falling back to the manual attention implementation. This warning can be removed using the argument `attn_implementation="eager"` when loading the model.'
"Note that this probably happens because `guidance_scale>1` or because you used `get_unconditional_inputs`. See https://github.com/huggingface/transformers/issues/31189 for more information."
)
return super().forward(
hidden_states,
key_value_states=key_value_states,
past_key_value=past_key_value,
attention_mask=attention_mask,
layer_head_mask=layer_head_mask,
output_attentions=output_attentions,
)
Comment on lines +582 to +589
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Rather than fallback, I would just raise an exception. Otherwise this expensive check and forward pass can easily go unnoticed

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@ylacombe ylacombe Jun 4, 2024

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Well, sdpa and guidance_scale>1 are used by default, so we'd raise the error almost every time. Also, even if the model uses eager mode for the cross-attention layers (in which the bug happens), it'll still benefit from the speed-up of the self-attention layers.

Should we find a better way of testing the attention mask ? For example, we could raise a warning that it will happens here and here and switch the cross-attention SDPA layers to eager layers by default when it happens?

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OK, I see. I'm a bit concerned about this causing unexpected behaviour, in particular defaulting to eager like this as it's a bit magic. As there's other layers which can still use SDPA, this seems like a pragmatic solution.

Let's leave as-is. If more users raise issues, then we'll have to re-think.


# if key_value_states are provided this layer is used as a cross-attention layer
# for the decoder
is_cross_attention = key_value_states is not None
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