[Model] Support Gemma2 embedding model (vllm-project#9004)

Signed-off-by: Amit Garg <mitgarg17495@gmail.com>

Author: xyang16

tests/conftest.py

@@ -277,6 +277,7 @@ def __init__(
                 SentenceTransformer(
                     model_name,
                     device="cpu",
+                    trust_remote_code=True,
                 ).to(dtype=torch_dtype))
         else:
             model_kwargs = model_kwargs if model_kwargs is not None else {}

tests/models/embedding/language/test_embedding.py

@@ -1,13 +1,14 @@
 """Compare the outputs of HF and vLLM for Mistral models using greedy sampling.
 
-Run `pytest tests/models/test_llama_embedding.py`.
+Run `pytest tests/models/embedding/language/test_embedding.py`.
 """
 import pytest
 import torch
 import torch.nn.functional as F
 
 MODELS = [
     "intfloat/e5-mistral-7b-instruct",
+    "BAAI/bge-multilingual-gemma2",
 ]
 
 
@@ -28,6 +29,14 @@ def test_models(
     model: str,
     dtype: str,
 ) -> None:
+    # The example_prompts has ending "\n", for example:
+    # "Write a short story about a robot that dreams for the first time.\n"
+    # sentence_transformers will strip the input texts, see:
+    # https://github.com/UKPLab/sentence-transformers/blob/v3.1.1/sentence_transformers/models/Transformer.py#L159
+    # This makes the input_ids different between hf_model and vllm_model.
+    # So we need to strip the input texts to avoid test failing.
+    example_prompts = [str(s).strip() for s in example_prompts]
+
     with hf_runner(model, dtype=dtype, is_embedding_model=True) as hf_model:
         hf_outputs = hf_model.encode(example_prompts)
 

vllm/model_executor/models/gemma2.py

@@ -278,11 +278,14 @@ def forward(
         kv_caches: List[torch.Tensor],
         attn_metadata: AttentionMetadata,
         intermediate_tensors: Optional[IntermediateTensors],
+        inputs_embeds: Optional[torch.Tensor] = None,
     ) -> Union[torch.Tensor, IntermediateTensors]:
         if get_pp_group().is_first_rank:
-            hidden_states = self.embed_tokens(input_ids)
+            if inputs_embeds is not None:
+                hidden_states = inputs_embeds
+            else:
+                hidden_states = self.embed_tokens(input_ids)
             hidden_states *= self.normalizer
-
             residual = None
         else:
             assert intermediate_tensors is not None

vllm/model_executor/models/gemma2_embedding.py

@@ -0,0 +1,82 @@
+from typing import Iterable, List, Optional, Tuple
+
+import torch
+from torch import nn
+
+from vllm.attention import AttentionMetadata
+from vllm.model_executor.layers.pooler import Pooler, PoolingType
+from vllm.model_executor.model_loader.weight_utils import default_weight_loader
+from vllm.model_executor.models.gemma2 import Gemma2Model
+from vllm.model_executor.pooling_metadata import PoolingMetadata
+from vllm.sequence import IntermediateTensors, PoolerOutput
+
+
+class Gemma2EmbeddingModel(nn.Module):
+    """A model that uses Gemma2 with additional embedding functionalities.
+
+   This class encapsulates the Gemma2Model and provides an interface for
+   embedding operations and customized pooling functions.
+
+   Attributes:
+       model: An instance of Gemma2Model used for forward operations.
+       _pooler: An instance of Pooler used for pooling operations.
+   """
+
+    def __init__(
+        self,
+        **kwargs,
+    ) -> None:
+        super().__init__()
+        self.model = Gemma2Model(**kwargs)
+        self._pooler = Pooler(pooling_type=PoolingType.LAST, normalize=True)
+
+    def forward(
+        self,
+        input_ids: Optional[torch.Tensor],
+        positions: torch.Tensor,
+        kv_caches: List[torch.Tensor],
+        attn_metadata: AttentionMetadata,
+        intermediate_tensors: Optional[IntermediateTensors] = None,
+        inputs_embeds: Optional[torch.Tensor] = None,
+    ) -> torch.Tensor:
+        return self.model.forward(input_ids, positions, kv_caches,
+                                  attn_metadata, intermediate_tensors,
+                                  inputs_embeds)
+
+    def pooler(
+        self,
+        hidden_states: torch.Tensor,
+        pooling_metadata: PoolingMetadata,
+    ) -> Optional[PoolerOutput]:
+        return self._pooler(hidden_states, pooling_metadata)
+
+    def load_weights(self, weights: Iterable[Tuple[str, torch.Tensor]]):
+        stacked_params_mapping = [
+            # (param_name, shard_name, shard_id)
+            ("qkv_proj", "q_proj", "q"),
+            ("qkv_proj", "k_proj", "k"),
+            ("qkv_proj", "v_proj", "v"),
+            ("gate_up_proj", "gate_proj", 0),
+            ("gate_up_proj", "up_proj", 1),
+        ]
+        params_dict = dict(self.model.named_parameters())
+        for name, loaded_weight in weights:
+            for (param_name, weight_name, shard_id) in stacked_params_mapping:
+                if weight_name not in name:
+                    continue
+                name = name.replace(weight_name, param_name)
+                # Skip loading extra bias for GPTQ models.
+                if name.endswith(".bias") and name not in params_dict:
+                    continue
+                param = params_dict[name]
+                weight_loader = param.weight_loader
+                weight_loader(param, loaded_weight, shard_id)
+                break
+            else:
+                # Skip loading extra bias for GPTQ models.
+                if name.endswith(".bias") and name not in params_dict:
+                    continue
+                param = params_dict[name]
+                weight_loader = getattr(param, "weight_loader",
+                                        default_weight_loader)
+                weight_loader(param, loaded_weight)

vllm/model_executor/models/registry.py

@@ -83,6 +83,7 @@
 _EMBEDDING_MODELS = {
     "MistralModel": ("llama_embedding", "LlamaEmbeddingModel"),
     "Qwen2ForRewardModel": ("qwen2_rm", "Qwen2ForRewardModel"),
+    "Gemma2Model": ("gemma2_embedding", "Gemma2EmbeddingModel"),
 }
 
 _MULTIMODAL_MODELS = {