[Bugfix] Merge MM embeddings by index instead of token IDs (#16229)
Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk> Signed-off-by: NickLucche <nlucches@redhat.com> Signed-off-by: Roger Wang <hey@rogerw.io> Co-authored-by: NickLucche <nlucches@redhat.com> Co-authored-by: Roger Wang <hey@rogerw.io>
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@@ -66,35 +66,12 @@ Further update the model as follows:
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!!! important
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The returned `multimodal_embeddings` must be either a **3D [torch.Tensor][]** of shape `(num_items, feature_size, hidden_size)`, or a **list / tuple of 2D [torch.Tensor][]'s** of shape `(feature_size, hidden_size)`, so that `multimodal_embeddings[i]` retrieves the embeddings generated from the `i`-th multimodal data item (e.g, image) of the request.
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- Implement [get_input_embeddings][vllm.model_executor.models.interfaces.SupportsMultiModal.get_input_embeddings] to merge `multimodal_embeddings` with text embeddings from the `input_ids`. If input processing for the model is implemented correctly (see sections below), then you can leverage the utility function we provide to easily merge the embeddings.
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!!! note
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By default, vLLM merges the multimodal embeddings into text embeddings depending on the information of their locations defined in
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[PlaceholderRange][vllm.multimodal.inputs.PlaceholderRange] from input processing.
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This logic can be found at [get_input_embeddings][vllm.model_executor.models.interfaces.SupportsMultiModal.get_input_embeddings].
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??? code
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```python
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from .utils import merge_multimodal_embeddings
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class YourModelForImage2Seq(nn.Module):
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...
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def get_input_embeddings(
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self,
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input_ids: torch.Tensor,
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multimodal_embeddings: Optional[MultiModalEmbeddings] = None,
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) -> torch.Tensor:
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# `get_input_embeddings` should already be implemented for the language
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# model as one of the requirements of basic vLLM model implementation.
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inputs_embeds = self.language_model.get_input_embeddings(input_ids)
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if multimodal_embeddings is not None:
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inputs_embeds = merge_multimodal_embeddings(
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input_ids=input_ids,
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inputs_embeds=inputs_embeds,
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multimodal_embeddings=multimodal_embeddings,
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placeholder_token_id=self.config.image_token_index)
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return inputs_embeds
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```
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You may override this method if additional logic is required for your model when merging embeddings.
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- Implement [get_language_model][vllm.model_executor.models.interfaces.SupportsMultiModal.get_language_model] getter to provide stable access to the underlying language model.
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