[TRTLLM-8413][chore] resolve sampling defaults in OpenAI API backend (#8121)

Signed-off-by: ixlmar <206748156+ixlmar@users.noreply.github.com>

Author: ixlmar

tensorrt_llm/serve/openai_protocol.py

@@ -220,8 +220,8 @@ class CompletionRequest(OpenAIBaseModel):
     stream: Optional[bool] = False
     stream_options: Optional[StreamOptions] = None
     suffix: Optional[str] = None
-    temperature: Optional[float] = 1.0
-    top_p: Optional[float] = 1.0
+    temperature: Optional[float] = None
+    top_p: Optional[float] = None
     user: Optional[str] = None
     lora_request: Optional[LoRARequest] = None
 
@@ -275,8 +275,9 @@ def to_sampling_params(self, vocab_size: int = 32000) -> SamplingParams:
             presence_penalty=self.presence_penalty,
             seed=self.seed,
             stop=self.stop,
-            temperature=self.temperature,
-            top_p=self.top_p,
+            temperature=(self.temperature
+                         if self.temperature is not None else 1.0),
+            top_p=(self.top_p if self.top_p is not None else 1.0),
 
             # completion-sampling-params
             use_beam_search=self.use_beam_search,
@@ -510,8 +511,8 @@ class ChatCompletionRequest(OpenAIBaseModel):
     stop: Optional[Union[str, List[str]]] = Field(default_factory=list)
     stream: Optional[bool] = False
     stream_options: Optional[StreamOptions] = None
-    temperature: Optional[float] = 1.0
-    top_p: Optional[float] = 1.0
+    temperature: Optional[float] = None
+    top_p: Optional[float] = None
     tools: Optional[List[ChatCompletionToolsParam]] = None
     tool_choice: Optional[Union[Literal["none", "auto"],
                                 ChatCompletionNamedToolChoiceParam]] = "none"
@@ -614,13 +615,14 @@ def to_sampling_params(self,
             presence_penalty=self.presence_penalty,
             seed=self.seed,
             stop=self.stop,
-            temperature=self.temperature,
+            temperature=(self.temperature
+                         if self.temperature is not None else 1.0),
 
             # chat-completion-sampling-params
             best_of=self.best_of,
             use_beam_search=self.use_beam_search,
             top_k=self.top_k,
-            top_p=self.top_p,
+            top_p=(self.top_p if self.top_p is not None else 1.0),
             top_p_min=self.top_p_min if self.top_p_min > 0 else None,
             min_p=self.min_p,
             repetition_penalty=self.repetition_penalty,