Vectorize logprobs computation (#787)

python/sglang/srt/layers/logits_processor.py

@@ -77,33 +77,46 @@ class LogitsProcessor(nn.Module):
 
     @staticmethod
     def get_top_logprobs(all_logprobs, logits_metadata: LogitsMetadata):
-        # TODO: vectorize the code below
         if logits_metadata.forward_mode == ForwardMode.DECODE:
             output_top_logprobs = []
-            for i in range(all_logprobs.shape[0]):
-                k = logits_metadata.top_logprobs_nums[i]
-                t = all_logprobs[i].topk(k)
-                v_cpu = t.values.tolist()
-                p_cpu = t.indices.tolist()
-                output_top_logprobs.append(list(zip(v_cpu, p_cpu)))
+            max_k = max(logits_metadata.top_logprobs_nums)
+            ret = all_logprobs.topk(max_k, dim=1)
+            values = ret.values.tolist()
+            indices = ret.indices.tolist()
+            for i, k in enumerate(logits_metadata.top_logprobs_nums):
+                output_top_logprobs.append(list(zip(values[i][:k], indices[i][:k])))
             return None, output_top_logprobs
         else:
+            # TODO: vectorize the code below
             input_top_logprobs, output_top_logprobs = [], []
             pt = 0
             extend_seq_lens_cpu = logits_metadata.extend_seq_lens.tolist()
+
+            max_k = max(logits_metadata.top_logprobs_nums)
+            ret = all_logprobs.topk(max_k, dim=1)
+            values = ret.values.tolist()
+            indices = ret.indices.tolist()
+
             for i, extend_seq_len in enumerate(extend_seq_lens_cpu):
                 if extend_seq_len == 0:
                     input_top_logprobs.append([])
                     output_top_logprobs.append([])
                     continue
                 k = logits_metadata.top_logprobs_nums[i]
-                t = all_logprobs[pt : pt + extend_seq_len].topk(k)
-                vs_cpu = t.values.tolist()
-                ps_cpu = t.indices.tolist()
                 input_top_logprobs.append(
-                    [list(zip(vs_cpu[j], ps_cpu[j])) for j in range(len(vs_cpu) - 1)]
+                    [
+                        list(zip(values[pt + j][:k], indices[pt + j][:k]))
+                        for j in range(extend_seq_len - 1)
+                    ]
+                )
+                output_top_logprobs.append(
+                    list(
+                        zip(
+                            values[pt + extend_seq_len - 1][:k],
+                            indices[pt + extend_seq_len - 1][:k],
+                        )
+                    )
                 )
-                output_top_logprobs.append(list(zip(vs_cpu[-1], ps_cpu[-1])))
                 pt += extend_seq_len
 
             return input_top_logprobs, output_top_logprobs

python/sglang/srt/managers/tokenizer_manager.py

@@ -6,7 +6,7 @@ import dataclasses
 import logging
 import multiprocessing as mp
 import os
-from typing import Dict, List
+from typing import Dict, List, Tuple
 
 import numpy as np
 import transformers
@@ -469,7 +469,9 @@ class TokenizerManager:
                 )
         return ret
 
-    def detokenize_logprob_tokens(self, token_logprobs, decode_to_text: bool):
+    def detokenize_logprob_tokens(
+        self, token_logprobs: List[Tuple[float, int]], decode_to_text: bool
+    ):
         if not decode_to_text:
             return [(logprob, token_id, None) for logprob, token_id in token_logprobs]
 
@@ -481,9 +483,13 @@ class TokenizerManager:
         ]
 
     def detokenize_top_logprobs_tokens(self, top_logprobs, decode_to_text: bool):
-        for i, t in enumerate(top_logprobs):
-            if t:
-                top_logprobs[i] = self.detokenize_logprob_tokens(t, decode_to_text)
+        # TODO: The current implementation only batches the detokenization for top-k tokens per single position.
+        # We should batch all top-k tokens in all positions.
+        for i, token_top_logprobs in enumerate(top_logprobs):
+            if token_top_logprobs:
+                top_logprobs[i] = self.detokenize_logprob_tokens(
+                    token_top_logprobs, decode_to_text
+                )
         return top_logprobs