Add support for `spaces_between_special_tokens`

vllm/engine/llm_engine.py

@@ -632,8 +632,7 @@ class LLMEngine:
                     f"CPU KV cache usage: {cpu_cache_usage * 100:.1f}%")
         self.last_logging_time = now
 
-    def _decode_sequence(self, seq: Sequence,
-                         sampling_params: SamplingParams) -> None:
+    def _decode_sequence(self, seq: Sequence, prms: SamplingParams) -> None:
         """Decodes the new token for a sequence."""
         (new_tokens, new_output_text, prefix_offset,
          read_offset) = detokenize_incrementally(
@@ -642,7 +641,8 @@ class LLMEngine:
              prev_tokens=seq.tokens,
              prefix_offset=seq.prefix_offset,
              read_offset=seq.read_offset,
-             skip_special_tokens=sampling_params.skip_special_tokens,
+             skip_special_tokens=prms.skip_special_tokens,
+             spaces_between_special_tokens=prms.spaces_between_special_tokens,
          )
         if seq.tokens is None:
             seq.tokens = new_tokens

vllm/entrypoints/openai/api_server.py

@@ -212,6 +212,7 @@ async def create_chat_completion(request: ChatCompletionRequest,
     request_id = f"cmpl-{random_uuid()}"
     created_time = int(time.monotonic())
     try:
+        spaces_between_special_tokens = request.spaces_between_special_tokens
         sampling_params = SamplingParams(
             n=request.n,
             presence_penalty=request.presence_penalty,
@@ -226,6 +227,7 @@ async def create_chat_completion(request: ChatCompletionRequest,
             ignore_eos=request.ignore_eos,
             use_beam_search=request.use_beam_search,
             skip_special_tokens=request.skip_special_tokens,
+            spaces_between_special_tokens=spaces_between_special_tokens,
         )
     except ValueError as e:
         return create_error_response(HTTPStatus.BAD_REQUEST, str(e))
@@ -413,6 +415,7 @@ async def create_completion(request: CompletionRequest, raw_request: Request):
 
     created_time = int(time.monotonic())
     try:
+        spaces_between_special_tokens = request.spaces_between_special_tokens
         sampling_params = SamplingParams(
             n=request.n,
             best_of=request.best_of,
@@ -428,6 +431,7 @@ async def create_completion(request: CompletionRequest, raw_request: Request):
             logprobs=request.logprobs,
             use_beam_search=request.use_beam_search,
             skip_special_tokens=request.skip_special_tokens,
+            spaces_between_special_tokens=spaces_between_special_tokens,
         )
     except ValueError as e:
         return create_error_response(HTTPStatus.BAD_REQUEST, str(e))

vllm/entrypoints/openai/protocol.py

@@ -72,6 +72,7 @@ class ChatCompletionRequest(BaseModel):
     use_beam_search: Optional[bool] = False
     stop_token_ids: Optional[List[int]] = Field(default_factory=list)
     skip_special_tokens: Optional[bool] = True
+    spaces_between_special_tokens: Optional[bool] = True
 
 
 class CompletionRequest(BaseModel):
@@ -98,6 +99,7 @@ class CompletionRequest(BaseModel):
     use_beam_search: Optional[bool] = False
     stop_token_ids: Optional[List[int]] = Field(default_factory=list)
     skip_special_tokens: Optional[bool] = True
+    spaces_between_special_tokens: Optional[bool] = True
 
 
 class LogProbs(BaseModel):

vllm/sampling_params.py

@@ -71,6 +71,8 @@ class SamplingParams:
             `logprobs+1` elements in the response.
         prompt_logprobs: Number of log probabilities to return per prompt token.
         skip_special_tokens: Whether to skip special tokens in the output.
+        spaces_between_special_tokens: Whether to add spaces between special
+            tokens in the output.  Defaults to True.
     """
 
     def __init__(
@@ -93,6 +95,7 @@ class SamplingParams:
         logprobs: Optional[int] = None,
         prompt_logprobs: Optional[int] = None,
         skip_special_tokens: bool = True,
+        spaces_between_special_tokens: bool = True,
     ) -> None:
         self.n = n
         self.best_of = best_of if best_of is not None else n
@@ -120,6 +123,7 @@ class SamplingParams:
         self.logprobs = logprobs
         self.prompt_logprobs = prompt_logprobs
         self.skip_special_tokens = skip_special_tokens
+        self.spaces_between_special_tokens = spaces_between_special_tokens
 
         self._verify_args()
         if self.use_beam_search:
@@ -222,4 +226,6 @@ class SamplingParams:
                 f"max_tokens={self.max_tokens}, "
                 f"logprobs={self.logprobs}, "
                 f"prompt_logprobs={self.prompt_logprobs}, "
-                f"skip_special_tokens={self.skip_special_tokens})")
+                f"skip_special_tokens={self.skip_special_tokens}, "
+                "spaces_between_special_tokens="
+                f"{self.spaces_between_special_tokens})")

vllm/transformers_utils/tokenizer.py

@@ -73,6 +73,7 @@ def _convert_tokens_to_string_with_added_encoders(
     tokenizer: Union[PreTrainedTokenizer, PreTrainedTokenizerFast],
     output_tokens: List[str],
     skip_special_tokens: bool,
+    spaces_between_special_tokens: bool,
 ) -> str:
     # Adapted from
     # https://github.com/huggingface/transformers/blob/v4.28.0/src/transformers/tokenization_utils.py#L921
@@ -96,7 +97,10 @@ def _convert_tokens_to_string_with_added_encoders(
     if current_sub_text:
         sub_text = tokenizer.convert_tokens_to_string(current_sub_text)
         sub_texts.append(sub_text)
-    return " ".join(sub_texts)
+    if spaces_between_special_tokens:
+        return " ".join(sub_texts)
+    else:
+        return "".join(sub_texts)
 
 
 # Based on
@@ -109,6 +113,7 @@ def detokenize_incrementally(
     prefix_offset: int = 0,
     read_offset: int = 0,
     skip_special_tokens: bool = False,
+    spaces_between_special_tokens: bool = True,
 ) -> Tuple[List[str], str, int, int]:
     new_token_id = all_input_ids[-1]
     # This is the first iteration for this sequence
@@ -143,11 +148,15 @@ def detokenize_incrementally(
         prefix_text = _convert_tokens_to_string_with_added_encoders(
             tokenizer,
             output_tokens[prefix_offset:read_offset],
-            skip_special_tokens=skip_special_tokens)
+            skip_special_tokens=skip_special_tokens,
+            spaces_between_special_tokens=spaces_between_special_tokens,
+        )
         new_text = _convert_tokens_to_string_with_added_encoders(
             tokenizer,
             output_tokens[prefix_offset:],
-            skip_special_tokens=skip_special_tokens)
+            skip_special_tokens=skip_special_tokens,
+            spaces_between_special_tokens=spaces_between_special_tokens,
+        )
 
     if len(new_text) > len(prefix_text) and not new_text.endswith("�"):
         # utf-8 char at the end means it's a potential unfinished byte sequence