[Feature] Add load generation config from model

examples/offline_inference_with_default_generation_config.py

@@ -0,0 +1,30 @@
+from vllm import LLM
+
+# Sample prompts.
+prompts = [
+    "Hello, my name is",
+    "The president of the United States is",
+    "The capital of France is",
+    "The future of AI is",
+]
+
+# Create an LLM with built-in default generation config.
+# The generation config is set to None by default to keep
+# the behavior consistent with the previous version.
+# If you want to use the default generation config from the model,
+# you should set the generation_config to "auto".
+llm = LLM(model="Qwen/Qwen2.5-0.5B-Instruct", generation_config="auto")
+
+# Load the default sampling parameters from the model.
+sampling_params = llm.get_default_sampling_params()
+# Modify the sampling parameters if needed.
+sampling_params.temperature = 0.5
+
+# Generate texts from the prompts. The output is a list of RequestOutput objects
+# that contain the prompt, generated text, and other information.
+outputs = llm.generate(prompts, sampling_params)
+# Print the outputs.
+for output in outputs:
+    prompt = output.prompt
+    generated_text = output.outputs[0].text
+    print(f"Prompt: {prompt!r}, Generated text: {generated_text!r}")

tests/entrypoints/openai/test_serving_chat.py

@@ -1,6 +1,7 @@
 import asyncio
 from contextlib import suppress
 from dataclasses import dataclass
+from typing import Optional
 from unittest.mock import MagicMock
 
 from vllm.config import MultiModalConfig
@@ -31,6 +32,10 @@ class MockModelConfig:
     multimodal_config = MultiModalConfig()
     hf_config = MockHFConfig()
     logits_processor_pattern = None
+    diff_sampling_param: Optional[dict] = None
+
+    def get_diff_sampling_param(self):
+        return self.diff_sampling_param or {}
 
 
 @dataclass
@@ -94,3 +99,59 @@ def test_serving_chat_should_set_correct_max_tokens():
         asyncio.run(serving_chat.create_chat_completion(req))
 
     assert mock_engine.generate.call_args.args[1].max_tokens == 10
+
+
+def test_serving_chat_could_load_correct_generation_config():
+
+    mock_model_config = MockModelConfig()
+    mock_model_config.diff_sampling_param = {
+        "temperature": 0.5,
+        "repetition_penalty": 1.05
+    }
+
+    mock_engine = MagicMock(spec=MQLLMEngineClient)
+    mock_engine.get_tokenizer.return_value = get_tokenizer(MODEL_NAME)
+    mock_engine.errored = False
+
+    # Initialize the serving chat
+    serving_chat = OpenAIServingChat(mock_engine,
+                                     mock_model_config,
+                                     BASE_MODEL_PATHS,
+                                     response_role="assistant",
+                                     chat_template=CHAT_TEMPLATE,
+                                     chat_template_content_format="auto",
+                                     lora_modules=None,
+                                     prompt_adapters=None,
+                                     request_logger=None)
+    req = ChatCompletionRequest(
+        model=MODEL_NAME,
+        messages=[{
+            "role": "user",
+            "content": "what is 1+1?"
+        }],
+        guided_decoding_backend="outlines",
+    )
+
+    with suppress(Exception):
+        asyncio.run(serving_chat.create_chat_completion(req))
+
+    assert mock_engine.generate.call_args.args[1].temperature == 0.5
+    assert mock_engine.generate.call_args.args[1].repetition_penalty == 1.05
+
+    # Test the param when user set it
+    req.temperature = 0.1
+
+    with suppress(Exception):
+        asyncio.run(serving_chat.create_chat_completion(req))
+
+    assert mock_engine.generate.call_args.args[1].temperature == 0.1
+    assert mock_engine.generate.call_args.args[1].repetition_penalty == 1.05
+
+    # Test When temperature==0.0
+    req.temperature = 0.0
+
+    with suppress(Exception):
+        asyncio.run(serving_chat.create_chat_completion(req))
+
+    assert mock_engine.generate.call_args.args[1].temperature == 0.0
+    assert mock_engine.generate.call_args.args[1].repetition_penalty == 1.05

vllm/config.py

@@ -26,7 +26,8 @@
 from vllm.transformers_utils.config import (
     ConfigFormat, get_config, get_hf_image_processor_config,
     get_hf_text_config, get_pooling_config,
-    get_sentence_transformer_tokenizer_config, is_encoder_decoder, uses_mrope)
+    get_sentence_transformer_tokenizer_config, is_encoder_decoder,
+    try_get_generation_config, uses_mrope)
 from vllm.utils import (GiB_bytes, LayerBlockType, cuda_device_count_stateless,
                         get_cpu_memory, print_warning_once, random_uuid,
                         resolve_obj_by_qualname)
@@ -160,6 +161,7 @@ class ModelConfig:
             logits processor qualified names that can be passed with the
             `logits_processors` extra completion argument. Defaults to None, 
             which allows no processors.
+        generation_config: Configuration parameter file for generation.
     """
 
     def __init__(self,
@@ -194,7 +196,8 @@ def __init__(self,
                  mm_cache_preprocessor: bool = False,
                  override_neuron_config: Optional[Dict[str, Any]] = None,
                  override_pooler_config: Optional["PoolerConfig"] = None,
-                 logits_processor_pattern: Optional[str] = None) -> None:
+                 logits_processor_pattern: Optional[str] = None,
+                 generation_config: Optional[str] = None) -> None:
         self.model = model
         self.tokenizer = tokenizer
         self.tokenizer_mode = tokenizer_mode
@@ -322,6 +325,8 @@ def __init__(self,
         self.pooler_config = self._init_pooler_config(override_pooler_config)
         self.logits_processor_pattern = logits_processor_pattern
 
+        self.generation_config = generation_config
+
         self._verify_quantization()
         self._verify_cuda_graph()
         self._verify_bnb_config()
@@ -787,6 +792,56 @@ def get_multimodal_config(self) -> "MultiModalConfig":
 
         return self.multimodal_config
 
+    def try_get_generation_config(self) -> Dict[str, Any]:
+        if self.generation_config is None or self.generation_config == "auto":
+            config = try_get_generation_config(
+                self.model,
+                trust_remote_code=self.trust_remote_code,
+                revision=self.revision,
+            )
+        else:
+            config = try_get_generation_config(
+                self.generation_config,
+                trust_remote_code=self.trust_remote_code,
+            )
+
+        if config is None:
+            return {}
+
+        return config.to_diff_dict()
+
+    def get_diff_sampling_param(self) -> Dict[str, Any]:
+        """
+        This method returns a dictionary containing the parameters 
+        that differ from the default sampling parameters, but only 
+        if `generation_config` is set. If `generation_config` is not 
+        set, an empty dictionary is returned.
+
+        Returns:
+            Dict[str, Any]: A dictionary with the differing sampling 
+            parameters if `generation_config` is set, otherwise an 
+            empty dictionary.
+        """
+        if self.generation_config is None:
+            # When generation_config is not set
+            return {}
+        config = self.try_get_generation_config()
+        available_params = [
+            "repetition_penalty",
+            "temperature",
+            "top_k",
+            "top_p",
+            "min_p",
+        ]
+        if any(p in config for p in available_params):
+            diff_sampling_param = {
+                p: config.get(p)
+                for p in available_params if config.get(p) is not None
+            }
+        else:
+            diff_sampling_param = {}
+        return diff_sampling_param
+
     @property
     def is_encoder_decoder(self) -> bool:
         """Extract the HF encoder/decoder model flag."""

vllm/engine/arg_utils.py

@@ -199,6 +199,8 @@ class EngineArgs:
 
     kv_transfer_config: Optional[KVTransferConfig] = None
 
+    generation_config: Optional[str] = None
+
     def __post_init__(self):
         if not self.tokenizer:
             self.tokenizer = self.model
@@ -941,6 +943,16 @@ def add_cli_args(parser: FlexibleArgumentParser) -> FlexibleArgumentParser:
             default="auto",
             help='The worker class to use for distributed execution.')
 
+        parser.add_argument(
+            "--generation-config",
+            type=nullable_str,
+            default=None,
+            help="The folder path to the generation config. "
+            "Defaults to None, will use the default generation config in vLLM. "
+            "If set to 'auto', the generation config will be automatically "
+            "loaded from model. If set to a folder path, the generation config "
+            "will be loaded from the specified folder path.")
+
         return parser
 
     @classmethod
@@ -984,7 +996,8 @@ def create_model_config(self) -> ModelConfig:
             mm_cache_preprocessor=self.mm_cache_preprocessor,
             override_neuron_config=self.override_neuron_config,
             override_pooler_config=self.override_pooler_config,
-            logits_processor_pattern=self.logits_processor_pattern)
+            logits_processor_pattern=self.logits_processor_pattern,
+            generation_config=self.generation_config)
 
     def create_load_config(self) -> LoadConfig:
         return LoadConfig(

vllm/engine/llm_engine.py

@@ -5,8 +5,8 @@
 from contextlib import contextmanager
 from dataclasses import dataclass
 from functools import partial
-from typing import (TYPE_CHECKING, Any, Callable, ClassVar, Deque, Dict,
-                    Iterable, List, Mapping, NamedTuple, Optional)
+from typing import (TYPE_CHECKING, Callable, ClassVar, Deque, Dict, Iterable,
+                    List, Mapping, NamedTuple, Optional)
 from typing import Sequence as GenericSequence
 from typing import Set, Type, Union, cast, overload
 
@@ -52,7 +52,6 @@
                            SequenceGroupOutput, SequenceStatus)
 from vllm.tracing import (SpanAttributes, SpanKind, extract_trace_context,
                           init_tracer)
-from vllm.transformers_utils.config import try_get_generation_config
 from vllm.transformers_utils.detokenizer import Detokenizer
 from vllm.transformers_utils.tokenizer import AnyTokenizer
 from vllm.transformers_utils.tokenizer_group import (
@@ -65,20 +64,6 @@
 logger = init_logger(__name__)
 _LOCAL_LOGGING_INTERVAL_SEC = 5
 
-
-def _load_generation_config_dict(model_config: ModelConfig) -> Dict[str, Any]:
-    config = try_get_generation_config(
-        model_config.model,
-        trust_remote_code=model_config.trust_remote_code,
-        revision=model_config.revision,
-    )
-
-    if config is None:
-        return {}
-
-    return config.to_diff_dict()
-
-
 _G = TypeVar("_G", bound=BaseTokenizerGroup, default=BaseTokenizerGroup)
 _O = TypeVar("_O", RequestOutput, PoolingRequestOutput)
 
@@ -274,8 +259,8 @@ def get_tokenizer_for_seq(sequence: Sequence) -> AnyTokenizer:
             return tokenizer_group.get_lora_tokenizer(sequence.lora_request)
 
         self.seq_counter = Counter()
-        self.generation_config_fields = _load_generation_config_dict(
-            self.model_config)
+        self.generation_config_fields = (
+            self.model_config.try_get_generation_config())
 
         self.input_preprocessor = InputPreprocessor(self.model_config,
                                                     self.tokenizer,

vllm/entrypoints/llm.py

@@ -258,6 +258,13 @@ def set_tokenizer(self, tokenizer: AnyTokenizer) -> None:
         else:
             tokenizer_group.tokenizer = get_cached_tokenizer(tokenizer)
 
+    def get_default_sampling_params(self) -> SamplingParams:
+        diff_sampling_param = (
+            self.llm_engine.model_config.get_diff_sampling_param())
+        if diff_sampling_param:
+            return SamplingParams.from_optional(**diff_sampling_param)
+        return SamplingParams()
+
     @overload
     def generate(
         self,
@@ -441,7 +448,7 @@ def generate(
 
         if sampling_params is None:
             # Use default sampling params.
-            sampling_params = SamplingParams()
+            sampling_params = self.get_default_sampling_params()
 
         self._validate_and_add_requests(
             prompts=parsed_prompts,