[Platform] Add custom default max tokens (#18557)

Signed-off-by: Gabriel Marinho <gmarinho@ibm.com>

vllm/entrypoints/openai/protocol.py

@@ -229,7 +229,6 @@ class ChatCompletionRequest(OpenAIBaseModel):
     logit_bias: Optional[dict[str, float]] = None
     logprobs: Optional[bool] = False
     top_logprobs: Optional[int] = 0
-    # TODO(#9845): remove max_tokens when field is removed from OpenAI API
     max_tokens: Optional[int] = Field(
         default=None,
         deprecated=
@@ -433,23 +432,10 @@ class ChatCompletionRequest(OpenAIBaseModel):
     }
 
     def to_beam_search_params(
-            self,
-            default_max_tokens: int,
-            default_sampling_params: Optional[dict] = None
-    ) -> BeamSearchParams:
-        # TODO(#9845): remove max_tokens when field is removed from OpenAI API
-        max_tokens = self.max_completion_tokens or self.max_tokens
+            self, max_tokens: int,
+            default_sampling_params: dict) -> BeamSearchParams:
 
-        if default_sampling_params is None:
-            default_sampling_params = {}
         n = self.n if self.n is not None else 1
-
-        # Use minimum of context window, user request & server limit.
-        max_tokens = min(
-            val for val in (default_max_tokens, max_tokens,
-                            default_sampling_params.get("max_tokens", None))
-            if val is not None)
-
         if (temperature := self.temperature) is None:
             temperature = default_sampling_params.get(
                 "temperature", self._DEFAULT_SAMPLING_PARAMS["temperature"])
@@ -465,21 +451,10 @@ class ChatCompletionRequest(OpenAIBaseModel):
 
     def to_sampling_params(
         self,
-        default_max_tokens: int,
+        max_tokens: int,
         logits_processor_pattern: Optional[str],
-        default_sampling_params: Optional[dict] = None,
+        default_sampling_params: dict,
     ) -> SamplingParams:
-        # TODO(#9845): remove max_tokens when field is removed from OpenAI API
-        max_tokens = self.max_completion_tokens or self.max_tokens
-
-        if default_sampling_params is None:
-            default_sampling_params = {}
-
-        # Use minimum of context window, user request & server limit.
-        max_tokens = min(
-            val for val in (default_max_tokens, max_tokens,
-                            default_sampling_params.get("max_tokens", None))
-            if val is not None)
 
         # Default parameters
         if (repetition_penalty := self.repetition_penalty) is None:
@@ -898,22 +873,15 @@ class CompletionRequest(OpenAIBaseModel):
     }
 
     def to_beam_search_params(
-            self,
-            default_max_tokens: int,
-            default_sampling_params: Optional[dict] = None
+        self,
+        max_tokens: int,
+        default_sampling_params: Optional[dict] = None,
     ) -> BeamSearchParams:
-        max_tokens = self.max_tokens
 
         if default_sampling_params is None:
             default_sampling_params = {}
         n = self.n if self.n is not None else 1
 
-        # Use minimum of context window, user request & server limit.
-        max_tokens = min(
-            val for val in (default_max_tokens, max_tokens,
-                            default_sampling_params.get("max_tokens", None))
-            if val is not None)
-
         if (temperature := self.temperature) is None:
             temperature = default_sampling_params.get("temperature", 1.0)
 
@@ -928,21 +896,14 @@ class CompletionRequest(OpenAIBaseModel):
 
     def to_sampling_params(
         self,
-        default_max_tokens: int,
+        max_tokens: int,
         logits_processor_pattern: Optional[str],
         default_sampling_params: Optional[dict] = None,
     ) -> SamplingParams:
-        max_tokens = self.max_tokens
 
         if default_sampling_params is None:
             default_sampling_params = {}
 
-        # Use minimum of context window, user request & server limit.
-        max_tokens = min(
-            val for val in (default_max_tokens, max_tokens,
-                            default_sampling_params.get("max_tokens", None))
-            if val is not None)
-
         # Default parameters
         if (repetition_penalty := self.repetition_penalty) is None:
             repetition_penalty = default_sampling_params.get(
@@ -1813,7 +1774,7 @@ class TranscriptionRequest(OpenAIBaseModel):
             self,
             default_max_tokens: int,
             default_sampling_params: Optional[dict] = None) -> SamplingParams:
-        # TODO(#9845): remove max_tokens when field is removed from OpenAI API
+
         max_tokens = default_max_tokens
 
         if default_sampling_params is None:
@@ -2029,7 +1990,7 @@ class TranslationRequest(OpenAIBaseModel):
             self,
             default_max_tokens: int,
             default_sampling_params: Optional[dict] = None) -> SamplingParams:
-        # TODO(#9845): remove max_tokens when field is removed from OpenAI API
+
         max_tokens = default_max_tokens
 
         if default_sampling_params is None:

vllm/entrypoints/openai/serving_chat.py

@@ -34,6 +34,7 @@ from vllm.entrypoints.openai.serving_models import OpenAIServingModels
 from vllm.entrypoints.openai.tool_parsers import ToolParser, ToolParserManager
 from vllm.entrypoints.openai.tool_parsers.mistral_tool_parser import (
     MistralToolCall)
+from vllm.entrypoints.utils import get_max_tokens
 from vllm.logger import init_logger
 from vllm.outputs import CompletionOutput, RequestOutput
 from vllm.reasoning import ReasoningParser, ReasoningParserManager
@@ -233,15 +234,22 @@ class OpenAIServingChat(OpenAIServing):
         try:
             for i, engine_prompt in enumerate(engine_prompts):
                 sampling_params: Union[SamplingParams, BeamSearchParams]
-                default_max_tokens = self.max_model_len - len(
-                    engine_prompt["prompt_token_ids"])
+
+                if self.default_sampling_params is None:
+                    self.default_sampling_params = {}
+
+                max_tokens = get_max_tokens(
+                    max_model_len=self.max_model_len,
+                    request=request,
+                    input_length=len(engine_prompt["prompt_token_ids"]),
+                    default_sampling_params=self.default_sampling_params)
+
                 if request.use_beam_search:
                     sampling_params = request.to_beam_search_params(
-                        default_max_tokens, self.default_sampling_params)
+                        max_tokens, self.default_sampling_params)
                 else:
                     sampling_params = request.to_sampling_params(
-                        default_max_tokens,
-                        self.model_config.logits_processor_pattern,
+                        max_tokens, self.model_config.logits_processor_pattern,
                         self.default_sampling_params)
 
                 self._log_inputs(request_id,

vllm/entrypoints/openai/serving_completion.py

@@ -33,6 +33,7 @@ from vllm.entrypoints.openai.serving_engine import (OpenAIServing,
                                                     is_text_tokens_prompt)
 # yapf: enable
 from vllm.entrypoints.openai.serving_models import OpenAIServingModels
+from vllm.entrypoints.utils import get_max_tokens
 from vllm.inputs.data import (EmbedsPrompt, TokensPrompt, is_embeds_prompt,
                               is_tokens_prompt)
 from vllm.logger import init_logger
@@ -160,15 +161,22 @@ class OpenAIServingCompletion(OpenAIServing):
                     input_length = len(engine_prompt["prompt_token_ids"])
                 else:
                     assert_never(engine_prompt)
-                default_max_tokens = self.max_model_len - input_length
+
+                if self.default_sampling_params is None:
+                    self.default_sampling_params = {}
+
+                max_tokens = get_max_tokens(
+                    max_model_len=self.max_model_len,
+                    request=request,
+                    input_length=input_length,
+                    default_sampling_params=self.default_sampling_params)
 
                 if request.use_beam_search:
                     sampling_params = request.to_beam_search_params(
-                        default_max_tokens, self.default_sampling_params)
+                        max_tokens, self.default_sampling_params)
                 else:
                     sampling_params = request.to_sampling_params(
-                        default_max_tokens,
-                        self.model_config.logits_processor_pattern,
+                        max_tokens, self.model_config.logits_processor_pattern,
                         self.default_sampling_params)
 
                 request_id_item = f"{request_id}-{i}"

vllm/entrypoints/utils.py

@@ -5,13 +5,17 @@ import argparse
 import asyncio
 import functools
 import os
-from typing import Any, Optional
+import sys
+from typing import Any, Optional, Union
 
 from fastapi import Request
 from fastapi.responses import JSONResponse, StreamingResponse
 from starlette.background import BackgroundTask, BackgroundTasks
 
+from vllm.entrypoints.openai.protocol import (ChatCompletionRequest,
+                                              CompletionRequest)
 from vllm.logger import init_logger
+from vllm.platforms import current_platform
 
 logger = init_logger(__name__)
 
@@ -181,7 +185,6 @@ def _validate_truncation_size(
 
 def show_filtered_argument_or_group_from_help(parser: argparse.ArgumentParser,
                                               subcommand_name: list[str]):
-    import sys
 
     # Only handle --help=<keyword> for the current subcommand.
     # Since subparser_init() runs for all subcommands during CLI setup,
@@ -242,3 +245,18 @@ def show_filtered_argument_or_group_from_help(parser: argparse.ArgumentParser,
             print(f"\nNo group or parameter matching '{search_keyword}'")
             print("Tip: use `--help=listgroup` to view all groups.")
             sys.exit(1)
+
+
+def get_max_tokens(max_model_len: int, request: Union[ChatCompletionRequest,
+                                                      CompletionRequest],
+                   input_length: int, default_sampling_params: dict) -> int:
+
+    max_tokens = getattr(request, "max_completion_tokens",
+                         None) or request.max_tokens
+    default_max_tokens = max_model_len - input_length
+    max_output_tokens = current_platform.get_max_output_tokens(input_length)
+
+    return min(val
+               for val in (default_max_tokens, max_tokens, max_output_tokens,
+                           default_sampling_params.get("max_tokens"))
+               if val is not None)

vllm/platforms/interface.py

@@ -4,6 +4,7 @@ import enum
 import os
 import platform
 import random
+import sys
 from datetime import timedelta
 from platform import uname
 from typing import TYPE_CHECKING, NamedTuple, Optional, Union
@@ -164,6 +165,9 @@ class Platform:
     def is_out_of_tree(self) -> bool:
         return self._enum == PlatformEnum.OOT
 
+    def get_max_output_tokens(self, prompt_len: int) -> int:
+        return sys.maxsize
+
     def is_cuda_alike(self) -> bool:
         """Stateless version of [torch.cuda.is_available][]."""
         return self._enum in (PlatformEnum.CUDA, PlatformEnum.ROCM)