[core] remove beam search from the core (#9105)

vllm/entrypoints/llm.py

@@ -28,7 +28,8 @@ from vllm.transformers_utils.tokenizer import (AnyTokenizer, MistralTokenizer,
                                                get_cached_tokenizer)
 from vllm.transformers_utils.tokenizer_group import TokenizerGroup
 from vllm.usage.usage_lib import UsageContext
-from vllm.utils import Counter, deprecate_kwargs, is_list_of
+from vllm.utils import (Counter, deprecate_kwargs, get_beam_search_score,
+                        is_list_of)
 
 logger = init_logger(__name__)
 
@@ -404,6 +405,12 @@ class LLM:
         max_tokens = params.max_tokens
         temperature = params.temperature
         ignore_eos = params.ignore_eos
+        length_penalty = params.length_penalty
+
+        def sort_beams_key(x: BeamSearchSequence) -> float:
+            return get_beam_search_score(x.tokens, x.cum_logprob,
+                                         tokenizer.eos_token_id,
+                                         length_penalty)
 
         tokenizer = self.get_tokenizer()
         # generate 2 * beam_width candidates at each step
@@ -466,7 +473,7 @@ class LLM:
                             else:
                                 instance_new_beams.append(new_beam)
                 sorted_beams = sorted(instance_new_beams,
-                                      key=lambda x: x.cum_logprob,
+                                      key=sort_beams_key,
                                       reverse=True)
                 instance.beams = sorted_beams[:beam_width]
 
@@ -474,7 +481,7 @@ class LLM:
         for instance in instances:
             instance.completed.extend(instance.beams)
             sorted_completed = sorted(instance.completed,
-                                      key=lambda x: x.cum_logprob,
+                                      key=sort_beams_key,
                                       reverse=True)
             best_beams = sorted_completed[:beam_width]