[Core] Gate `prompt_embeds` behind a feature flag (#17607)

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

tests/engine/test_skip_tokenizer_init.py → tests/engine/test_options.py

 # SPDX-License-Identifier: Apache-2.0
+from contextlib import nullcontext
 
 import pytest
 
@@ -14,6 +15,7 @@ def test_skip_tokenizer_initialization(model: str):
     llm = LLM(
         model=model,
         skip_tokenizer_init=True,
+        enforce_eager=True,
     )
     sampling_params = SamplingParams(prompt_logprobs=True, detokenize=True)
 
@@ -27,3 +29,32 @@ def test_skip_tokenizer_initialization(model: str):
     assert len(completions) > 0
     assert completions[0].text == ""
     assert completions[0].token_ids
+
+
+@pytest.mark.parametrize("model", ["distilbert/distilgpt2"])
+@pytest.mark.parametrize("enable_prompt_embeds", [True, False])
+def test_enable_prompt_embeds(hf_runner, model: str,
+                              enable_prompt_embeds: bool):
+    prompt = "abc"
+
+    with hf_runner(model) as hf_model:
+        token_ids = hf_model.tokenizer(prompt, return_tensors="pt").input_ids
+        token_ids = token_ids.to(hf_model.model.device)
+
+        embed_layer = hf_model.model.get_input_embeddings()
+        prompt_embeds = embed_layer(token_ids).squeeze(0)
+
+    ctx = (nullcontext() if enable_prompt_embeds else pytest.raises(
+        ValueError, match="set `--enable-prompt-embeds`"))
+
+    # This test checks if the flag skip_tokenizer_init skips the initialization
+    # of tokenizer and detokenizer. The generated output is expected to contain
+    # token ids.
+    llm = LLM(
+        model=model,
+        enable_prompt_embeds=enable_prompt_embeds,
+        enforce_eager=True,
+    )
+
+    with ctx:
+        llm.generate({"prompt_embeds": prompt_embeds})

tests/models/language/generation/test_common.py

@@ -109,12 +109,15 @@ def test_models(hf_runner, vllm_runner, example_prompts, model: str,
         # in parts of the operators
         pytest.skip(f"Skipping '{model}' model test with AITER kernel.")
 
+    use_prompt_embeds = os.getenv("VLLM_USE_V1") == "0"
+
     with hf_runner(model) as hf_model:
         hf_outputs = hf_model.generate_greedy_logprobs_limit(
             example_prompts, max_tokens, num_logprobs)
 
-        prompt_embeds: Optional[list[torch.Tensor]] = [] if os.getenv(
-            "VLLM_USE_V1") == "0" else None
+        prompt_embeds: Optional[list[torch.Tensor]] = ([] if use_prompt_embeds
+                                                       else None)
+
         prompt_token_ids = []
         for prompt in example_prompts:
             token_ids = hf_model.tokenizer(prompt,
@@ -131,6 +134,7 @@ def test_models(hf_runner, vllm_runner, example_prompts, model: str,
             tokenizer_mode=model_info.tokenizer_mode,
             trust_remote_code=model_info.trust_remote_code,
             max_num_seqs=2,
+            enable_prompt_embeds=use_prompt_embeds,
     ) as vllm_model:
         vllm_outputs = vllm_model.generate_greedy_logprobs(
             example_prompts, max_tokens, num_logprobs)

tests/worker/test_model_runner.py

@@ -43,6 +43,7 @@ def test_prepare_prompt(batch_size, use_prompt_embeds, monkeypatch):
         max_num_batched_tokens=100000,
         max_num_seqs=100000,
         enable_chunked_prefill=False,
+        enable_prompt_embeds=True,
     )
 
     seq_lens: list[int] = []
@@ -179,6 +180,7 @@ def test_prepare_decode_cuda_graph(batch_size, use_prompt_embeds, monkeypatch):
         max_num_batched_tokens=100000,
         max_num_seqs=100000,
         enable_chunked_prefill=False,
+        enable_prompt_embeds=True,
     )
 
     context_lens: list[int] = []
@@ -359,6 +361,7 @@ def test_hybrid_batches(batch_size, enforce_eager, use_prompt_embeds,
         max_num_batched_tokens=100000,
         max_num_seqs=100000,
         enable_chunked_prefill=True,
+        enable_prompt_embeds=True,
     )
 
     # Add prefill requests.

vllm/config.py

@@ -321,6 +321,10 @@ class ModelConfig:
     """Skip initialization of tokenizer and detokenizer. Expects valid
     `prompt_token_ids` and `None` for prompt from the input. The generated
     output will contain token ids."""
+    enable_prompt_embeds: bool = False
+    """If `True`, enables passing text embeddings as inputs via the
+    `prompt_embeds` key. Note that enabling this will double the time required
+    for graph compilation."""
     served_model_name: Optional[Union[str, list[str]]] = None
     """The model name(s) used in the API. If multiple names are provided, the
     server will respond to any of the provided names. The model name in the

vllm/engine/arg_utils.py

@@ -234,6 +234,7 @@ class EngineArgs:
     hf_config_path: Optional[str] = ModelConfig.hf_config_path
     task: TaskOption = ModelConfig.task
     skip_tokenizer_init: bool = ModelConfig.skip_tokenizer_init
+    enable_prompt_embeds: bool = ModelConfig.enable_prompt_embeds
     tokenizer_mode: TokenizerMode = ModelConfig.tokenizer_mode
     trust_remote_code: bool = ModelConfig.trust_remote_code
     allowed_local_media_path: str = ModelConfig.allowed_local_media_path
@@ -445,6 +446,8 @@ class EngineArgs:
                                  **model_kwargs["disable_cascade_attn"])
         model_group.add_argument("--skip-tokenizer-init",
                                  **model_kwargs["skip_tokenizer_init"])
+        model_group.add_argument("--enable-prompt-embeds",
+                                 **model_kwargs["enable_prompt_embeds"])
         model_group.add_argument("--served-model-name",
                                  **model_kwargs["served_model_name"])
         # This one is a special case because it is the
@@ -874,6 +877,7 @@ class EngineArgs:
             disable_sliding_window=self.disable_sliding_window,
             disable_cascade_attn=self.disable_cascade_attn,
             skip_tokenizer_init=self.skip_tokenizer_init,
+            enable_prompt_embeds=self.enable_prompt_embeds,
             served_model_name=self.served_model_name,
             limit_mm_per_prompt=self.limit_mm_per_prompt,
             use_async_output_proc=not self.disable_async_output_proc,

vllm/inputs/preprocess.py

@@ -303,8 +303,11 @@ class InputPreprocessor:
         self,
         parsed_content: EmbedsPrompt,
     ) -> EmbedsInputs:
+        if not self.model_config.enable_prompt_embeds:
+            raise ValueError("You must set `--enable-prompt-embeds` to input "
+                             "`prompt_embeds`.")
         if envs.VLLM_USE_V1:
-            raise ValueError("prompt_embeds is only available in V0.")
+            raise ValueError("`prompt_embeds` is only available in V0.")
 
         prompt_embeds = parsed_content["prompt_embeds"]
 

vllm/worker/model_runner.py

@@ -1565,7 +1565,9 @@ class GPUModelRunnerBase(ModelRunnerBase[TModelInputForGPU]):
                 # product.
                 cudagraph_capture_sizes = self.vllm_config.compilation_config\
                     .cudagraph_capture_sizes
-                cudagraph_inputs_embeds = (True, False)
+                cudagraph_inputs_embeds = ((
+                    True, False) if self.model_config.enable_prompt_embeds else
+                                           (False, ))
                 compilation_cases = itertools.product(
                     cudagraph_capture_sizes,
                     cudagraph_inputs_embeds,