vllm.model_executor.models.transformers.pooling ¶

class EmbeddingMixin(VllmModelForPooling):
    default_pooling_type = "CLS"

    def __init__(self, *, vllm_config: "VllmConfig", prefix: str = ""):
        # Skip VllmModelForPooling.__init__ and call the next class in MRO
        super(VllmModelForPooling, self).__init__(
            vllm_config=vllm_config, prefix=prefix
        )

        pooler_config = vllm_config.model_config.pooler_config
        assert pooler_config is not None

        self.pooler = DispatchPooler(
            {
                "token_embed": Pooler.for_token_embed(pooler_config),
                "embed": Pooler.for_embed(pooler_config),
            }
        )

class SequenceClassificationMixin(SupportsCrossEncoding, VllmModelForPooling):
    default_pooling_type = "CLS"

    def __init__(self, *, vllm_config: "VllmConfig", prefix: str = ""):
        # Skip VllmModelForPooling.__init__ and call the next class in MRO
        super(VllmModelForPooling, self).__init__(
            vllm_config=vllm_config, prefix=prefix
        )

        pooler_config = vllm_config.model_config.pooler_config
        assert pooler_config is not None

        # Certain information about the the model and classifier can only be
        # inferred from the `ForSequenceClassification` class. Therefore, we
        # instantiate it on the "meta" device to avoid allocating GPU memory.
        with torch.device("meta"):
            seq_cls_model = AutoModelForSequenceClassification.from_config(
                self.config,
                dtype=self.model_config.dtype,
                trust_remote_code=self.model_config.trust_remote_code,
            )

        # When used for sequence classification, some models have their
        # pooling layers removed. Make sure this is reflected in vLLM.
        for module in seq_cls_model.modules():
            if hasattr(module, "pooler") and module.pooler is None:
                self.model.pooler = None
                break
        if self.model.pooler is not None:
            raise ValueError(
                "Sequence classification models with pooling layers are not "
                "supported yet in the Transformers backend."
            )

        # Unlike `lm_head`, `classifier` is not always `nn.Linear`.
        self.classifier = seq_cls_model.classifier
        self.init_parameters(self.classifier, dtype=self.model_config.head_dtype)

        class ClassifierWithReshape(self.classifier.__class__):
            """CLSPool has already been applied in `pooling`.
            Add dim to match expected input shape of `classifier.forward`."""

            def forward(self, *args, **kwargs):
                if len(args) > 0:
                    args = (args[0].unsqueeze(1), *args[1:])
                return super().forward(*args, **kwargs)

        self.classifier.__class__ = ClassifierWithReshape

        self.pooler = DispatchPooler(
            {
                "token_classify": Pooler.for_token_classify(
                    pooler_config, classifier=self.classifier
                ),
                "classify": ClassifierPooler(
                    pooling=CLSPool(), classifier=self.classifier, act_fn="classify"
                ),
                "score": ClassifierPooler(
                    pooling=CLSPool(), classifier=self.classifier, act_fn="score"
                ),
            }
        )