Refactor logprob computation to return the real logprob used in sampling (#2664)

python/sglang/srt/layers/logits_processor.py

@@ -17,6 +17,8 @@ import dataclasses
 from typing import List, Optional, Union
 
 import torch
+import triton
+import triton.language as tl
 from torch import nn
 from vllm.distributed import (
     get_tensor_model_parallel_world_size,
@@ -33,51 +35,55 @@ from sglang.srt.model_executor.forward_batch_info import (
 
 @dataclasses.dataclass
 class LogitsProcessorOutput:
+    ## First part. This part will be returned by python/sglang/srt/layers/logits_processor.py::LogitsProcessor.
     # The logits of the next tokens.       shape: [#seq, vocab_size]
     next_token_logits: torch.Tensor
-    # The logprobs of the next tokens.     shape: [#seq, vocab_size]
-    next_token_logprobs: torch.Tensor = None
+    # Used by speculative decoding (EAGLE)
+    # The last hidden layers
+    hidden_states: Optional[torch.Tensor] = None
+
+    ## Second part. This part will be returned by python/sglang/srt/layers/sampler.py::Sampler.
+    # The logprobs of the next tokens.                              shape: [#seq]
+    next_token_logprobs: Optional[torch.Tensor] = None
+    # The logprobs and ids of the top-k tokens in output positions. shape: [#seq, k]
+    next_token_top_logprobs_val: Optional[List] = None
+    next_token_top_logprobs_idx: Optional[List] = None
 
+    ## Third part. This part will be returned by python/sglang/srt/layers/logits_processor.py::LogitsProcessor. Prefill-only.
     # The normlaized logprobs of prompts.  shape: [#seq]
     normalized_prompt_logprobs: torch.Tensor = None
-    # The logprobs of input tokens.        shape: [#token, vocab_size]
+    # The logprobs of input tokens.        shape: [#token]
     input_token_logprobs: torch.Tensor = None
-
-    # The logprob and id of the top-k tokens in input positions.  shape [#seq, #token, k]
+    # The logprobs and ids of the top-k tokens in input positions.  shape: [#seq, #token, k]
     input_top_logprobs_val: List = None
     input_top_logprobs_idx: List = None
-    # The logprob and id of the top-k tokens in output positions. shape [#seq, #token, k]
-    output_top_logprobs_val: List = None
-    output_top_logprobs_idx: List = None
-
-    # Used by speculative decoding (EAGLE)
-    # The output of transformer layers
-    hidden_states: Optional[torch.Tensor] = None
 
 
 @dataclasses.dataclass
 class LogitsMetadata:
     forward_mode: ForwardMode
-    top_logprobs_nums: Optional[List[int]]
-
-    return_logprob: bool = False
-    return_top_logprob: bool = False
+    capture_hidden_mode: CaptureHiddenMode = CaptureHiddenMode.NULL
 
+    extend_return_logprob: bool = False
+    extend_return_top_logprob: bool = False
     extend_seq_lens: Optional[torch.Tensor] = None
     extend_seq_lens_cpu: Optional[List[int]] = None
-
     extend_logprob_start_lens_cpu: Optional[List[int]] = None
     extend_logprob_pruned_lens_cpu: Optional[List[int]] = None
-
-    capture_hidden_mode: CaptureHiddenMode = CaptureHiddenMode.NULL
+    top_logprobs_nums: Optional[List[int]] = None
 
     @classmethod
     def from_forward_batch(cls, forward_batch: ForwardBatch):
-        extend_logprob_pruned_lens_cpu = None
+        if forward_batch.spec_info:
+            capture_hidden_mode = forward_batch.spec_info.capture_hidden_mode
+        else:
+            capture_hidden_mode = CaptureHiddenMode.NULL
 
-        if forward_batch.return_logprob:
-            return_top_logprob = any(x > 0 for x in forward_batch.top_logprobs_nums)
-            if forward_batch.forward_mode.is_extend():
+        if forward_batch.forward_mode.is_extend() and forward_batch.return_logprob:
+            extend_return_logprob = True
+            extend_return_top_logprob = any(
+                x > 0 for x in forward_batch.top_logprobs_nums
+            )
             extend_logprob_pruned_lens_cpu = [
                 extend_len - start_len
                 for extend_len, start_len in zip(
@@ -86,23 +92,20 @@ class LogitsMetadata:
                 )
             ]
         else:
-            return_top_logprob = False
-
-        if forward_batch.spec_info:
-            capture_hidden_mode = forward_batch.spec_info.capture_hidden_mode
-        else:
-            capture_hidden_mode = CaptureHiddenMode.NULL
+            extend_return_logprob = extend_return_top_logprob = (
+                extend_logprob_pruned_lens_cpu
+            ) = False
 
         return cls(
             forward_mode=forward_batch.forward_mode,
-            top_logprobs_nums=forward_batch.top_logprobs_nums,
-            return_logprob=forward_batch.return_logprob,
-            return_top_logprob=return_top_logprob,
+            capture_hidden_mode=capture_hidden_mode,
+            extend_return_logprob=extend_return_logprob,
+            extend_return_top_logprob=extend_return_top_logprob,
             extend_seq_lens=forward_batch.extend_seq_lens,
             extend_seq_lens_cpu=forward_batch.extend_seq_lens_cpu,
             extend_logprob_start_lens_cpu=forward_batch.extend_logprob_start_lens_cpu,
             extend_logprob_pruned_lens_cpu=extend_logprob_pruned_lens_cpu,
-            capture_hidden_mode=capture_hidden_mode,
+            top_logprobs_nums=forward_batch.top_logprobs_nums,
         )
 
 
@@ -129,7 +132,6 @@ class LogitsProcessor(nn.Module):
     ):
         if isinstance(logits_metadata, ForwardBatch):
             logits_metadata = LogitsMetadata.from_forward_batch(logits_metadata)
-        assert isinstance(logits_metadata, LogitsMetadata)
 
         # Get the last hidden states and last logits for the next token prediction
         if (
@@ -142,18 +144,10 @@ class LogitsProcessor(nn.Module):
             last_index = torch.cumsum(logits_metadata.extend_seq_lens, dim=0) - 1
             last_hidden = hidden_states[last_index]
 
+        # Compute logits
         last_logits = self._get_logits(last_hidden, lm_head)
-        if self.do_tensor_parallel_all_gather:
-            last_logits = tensor_model_parallel_all_gather(last_logits)
-        last_logits = last_logits[:, : self.config.vocab_size].float()
-
-        if self.final_logit_softcapping:
-            last_logits.div_(self.final_logit_softcapping)
-            torch.tanh(last_logits, out=last_logits)
-            last_logits.mul_(self.final_logit_softcapping)
-
-        # Return only last_logits if logprob is not requested
-        if not logits_metadata.return_logprob:
+        if not logits_metadata.extend_return_logprob:
+            # Decode mode or extend mode without return_logprob.
             return LogitsProcessorOutput(
                 next_token_logits=last_logits,
                 hidden_states=(
@@ -166,74 +160,42 @@ class LogitsProcessor(nn.Module):
                     )
                 ),
             )
-        else:
-            last_logprobs = self.compute_temp_top_p_normalized_logprobs(
-                last_logits, logits_metadata
-            )
-
-            if logits_metadata.forward_mode.is_decode():
-                if logits_metadata.return_top_logprob:
-                    output_top_logprobs_val, output_top_logprobs_idx = (
-                        self.get_top_logprobs(last_logprobs, logits_metadata)[2:4]
-                    )
-                else:
-                    output_top_logprobs_val = output_top_logprobs_idx = None
-                return LogitsProcessorOutput(
-                    next_token_logits=last_logits,
-                    next_token_logprobs=last_logprobs,
-                    output_top_logprobs_val=output_top_logprobs_val,
-                    output_top_logprobs_idx=output_top_logprobs_idx,
-                )
         else:
             # Slice the requested tokens to compute logprob
-                pt, states, pruned_input_ids = 0, [], []
+            pt, pruned_states, pruned_input_ids = 0, [], []
             for start_len, extend_len in zip(
                 logits_metadata.extend_logprob_start_lens_cpu,
                 logits_metadata.extend_seq_lens_cpu,
             ):
-                    states.append(hidden_states[pt + start_len : pt + extend_len])
+                pruned_states.append(hidden_states[pt + start_len : pt + extend_len])
                 pruned_input_ids.append(input_ids[pt + start_len : pt + extend_len])
                 pt += extend_len
 
-                # Compute the logits and logprobs for all required tokens
-                states = torch.cat(states, dim=0)
-                all_logits = self._get_logits(states, lm_head)
-                if self.do_tensor_parallel_all_gather:
-                    all_logits = tensor_model_parallel_all_gather(all_logits)
-
-                # The LM head's weights may be zero-padded for parallelism. Remove any
-                # extra logits that this padding may have produced.
-                all_logits = all_logits[:, : self.config.vocab_size].float()
-
-                if self.final_logit_softcapping:
-                    all_logits.div_(self.final_logit_softcapping)
-                    torch.tanh(all_logits, out=all_logits)
-                    all_logits.mul_(self.final_logit_softcapping)
-
-                all_logprobs = all_logits
-                del all_logits, hidden_states
+            # Compute the logits of all required tokens
+            pruned_states = torch.cat(pruned_states)
+            del hidden_states
+            input_token_logits = self._get_logits(pruned_states, lm_head)
+            del pruned_states
 
-                all_logprobs = self.compute_temp_top_p_normalized_logprobs(
-                    all_logprobs, logits_metadata
+            # Normalize the logprob w/o temperature, top-p
+            input_logprobs = input_token_logits
+            input_logprobs = self.compute_temp_top_p_normalized_logprobs(
+                input_logprobs, logits_metadata
             )
 
             # Get the logprob of top-k tokens
-                if logits_metadata.return_top_logprob:
+            if logits_metadata.extend_return_top_logprob:
                 (
                     input_top_logprobs_val,
                     input_top_logprobs_idx,
-                        output_top_logprobs_val,
-                        output_top_logprobs_idx,
-                    ) = self.get_top_logprobs(all_logprobs, logits_metadata)
+                ) = self.get_top_logprobs(input_logprobs, logits_metadata)
             else:
-                    input_top_logprobs_val = input_top_logprobs_idx = (
-                        output_top_logprobs_val
-                    ) = output_top_logprobs_idx = None
+                input_top_logprobs_val = input_top_logprobs_idx = None
 
             # Compute the normalized logprobs for the requested tokens.
             # Note that we pad a zero at the end for easy batching.
-                input_token_logprobs = all_logprobs[
-                    torch.arange(all_logprobs.shape[0], device="cuda"),
+            input_token_logprobs = input_logprobs[
+                torch.arange(input_logprobs.shape[0], device="cuda"),
                 torch.cat(
                     [
                         torch.cat(pruned_input_ids)[1:],
@@ -248,13 +210,10 @@ class LogitsProcessor(nn.Module):
 
             return LogitsProcessorOutput(
                 next_token_logits=last_logits,
-                    next_token_logprobs=last_logprobs,
                 normalized_prompt_logprobs=normalized_prompt_logprobs,
                 input_token_logprobs=input_token_logprobs,
                 input_top_logprobs_val=input_top_logprobs_val,
                 input_top_logprobs_idx=input_top_logprobs_idx,
-                    output_top_logprobs_val=output_top_logprobs_val,
-                    output_top_logprobs_idx=output_top_logprobs_idx,
             )
 
     def _get_logits(
@@ -269,9 +228,19 @@ class LogitsProcessor(nn.Module):
             # GGUF models
             logits = lm_head.linear_method.apply(lm_head, hidden_states, embedding_bias)
 
-        # Optional scaling factor
         if self.logit_scale is not None:
-            logits.mul_(self.logit_scale)  # In-place multiply
+            logits.mul_(self.logit_scale)
+
+        if self.do_tensor_parallel_all_gather:
+            logits = tensor_model_parallel_all_gather(logits)
+
+        # Compute the normalized logprobs for the requested tokens.
+        # Note that we pad a zero at the end for easy batching.
+        logits = logits[:, : self.config.vocab_size].float()
+
+        if self.final_logit_softcapping:
+            fused_softcap(logits, self.final_logit_softcapping)
+
         return logits
 
     @staticmethod
@@ -302,16 +271,7 @@ class LogitsProcessor(nn.Module):
         values = ret.values.tolist()
         indices = ret.indices.tolist()
 
-        if logits_metadata.forward_mode.is_decode():
-            output_top_logprobs_val = []
-            output_top_logprobs_idx = []
-            for i, k in enumerate(logits_metadata.top_logprobs_nums):
-                output_top_logprobs_val.append(values[i][:k])
-                output_top_logprobs_idx.append(indices[i][:k])
-            return None, None, output_top_logprobs_val, output_top_logprobs_idx
-        else:
         input_top_logprobs_val, input_top_logprobs_idx = [], []
-            output_top_logprobs_val, output_top_logprobs_idx = [], []
 
         pt = 0
         for k, pruned_len in zip(
@@ -321,8 +281,6 @@ class LogitsProcessor(nn.Module):
             if pruned_len <= 0:
                 input_top_logprobs_val.append([])
                 input_top_logprobs_idx.append([])
-                    output_top_logprobs_val.append([])
-                    output_top_logprobs_idx.append([])
                 continue
 
             input_top_logprobs_val.append(
@@ -331,61 +289,55 @@ class LogitsProcessor(nn.Module):
             input_top_logprobs_idx.append(
                 [indices[pt + j][:k] for j in range(pruned_len - 1)]
             )
-                output_top_logprobs_val.append(
-                    list(
-                        values[pt + pruned_len - 1][:k],
-                    )
-                )
-                output_top_logprobs_idx.append(
-                    list(
-                        indices[pt + pruned_len - 1][:k],
-                    )
-                )
             pt += pruned_len
 
-            return (
-                input_top_logprobs_val,
-                input_top_logprobs_idx,
-                output_top_logprobs_val,
-                output_top_logprobs_idx,
-            )
+        return input_top_logprobs_val, input_top_logprobs_idx
 
     @staticmethod
     def compute_temp_top_p_normalized_logprobs(
         last_logits: torch.Tensor, logits_metadata: LogitsMetadata
     ) -> torch.Tensor:
+        # TODO: Implement the temp and top-p normalization
         return torch.nn.functional.log_softmax(last_logits, dim=-1)
 
 
-def test():
-    all_logprobs = torch.tensor(
-        #       s                     s                s
-        [[0, 1, 2, 3], [1, 2, 3, 4], [2, 3, 4, 5], [3, 4, 5, 6], [4, 5, 6, 7]],
-        dtype=torch.float32,
-        device="cuda",
-    )
-    seq_lens = torch.tensor([2, 0, 3, 0], dtype=torch.int32, device="cuda")
-    input_ids = torch.tensor([1, 2, 3, 0, 1], dtype=torch.int32, device="cuda")
+@triton.jit
+def fused_softcap_kernel(
+    full_logits_ptr,
+    softcapping_value,
+    n_elements,
+    BLOCK_SIZE: tl.constexpr,
+):
+    pid = tl.program_id(0)
+    block_start = pid * BLOCK_SIZE
+    offsets = block_start + tl.arange(0, BLOCK_SIZE)
+    mask = offsets < n_elements
 
-    token_logprobs = all_logprobs[
-        torch.arange(all_logprobs.shape[0], device="cuda"),
-        torch.cat([input_ids[1:], torch.tensor([0], device="cuda")]),
-    ]
-    logprobs_cumsum = torch.cumsum(token_logprobs, dim=0, dtype=torch.float32)
+    # Load values
+    x = tl.load(full_logits_ptr + offsets, mask=mask)
 
-    len_cumsum = torch.cumsum(seq_lens, dim=0)
-    start = torch.cat((torch.tensor([0], device="cuda"), len_cumsum[:-1]), 0)
-    end = start + seq_lens - 2
-    start.clamp_(min=0, max=token_logprobs.shape[0] - 1)
-    end.clamp_(min=0, max=token_logprobs.shape[0] - 1)
-    sum_logp = logprobs_cumsum[end] - logprobs_cumsum[start] + token_logprobs[start]
+    # Perform operations in-place
+    x = x / softcapping_value
 
-    # assert logprobs == [2, _, 2, 4, _]
-    print("token logprobs", token_logprobs)
-    print("start", start)
-    print("end", end)
-    print("sum_logp", sum_logp)
+    # Manual tanh implementation using exp
+    exp2x = tl.exp(2 * x)
+    x = (exp2x - 1) / (exp2x + 1)
 
+    x = x * softcapping_value
 
-if __name__ == "__main__":
-    test()
+    # Store result
+    tl.store(full_logits_ptr + offsets, x, mask=mask)
+
+
+def fused_softcap(full_logits, final_logit_softcapping):
+    n_elements = full_logits.numel()
+    BLOCK_SIZE = 1024
+    grid = ((n_elements + BLOCK_SIZE - 1) // BLOCK_SIZE, 1, 1)
+
+    fused_softcap_kernel[grid](
+        full_logits_ptr=full_logits,
+        softcapping_value=final_logit_softcapping,
+        n_elements=n_elements,
+        BLOCK_SIZE=BLOCK_SIZE,
+    )
+    return full_logits

python/sglang/srt/layers/sampler.py

 import logging
-from typing import Union
+from typing import List
 
 import torch
 from torch import nn
@@ -28,13 +28,12 @@ class Sampler(nn.Module):
 
     def forward(
         self,
-        logits: Union[torch.Tensor, LogitsProcessorOutput],
+        logits_output: LogitsProcessorOutput,
         sampling_info: SamplingBatchInfo,
+        return_logprob: bool,
+        top_logprobs_nums: List[int],
     ):
-        if isinstance(logits, LogitsProcessorOutput):
-            logits = logits.next_token_logits
-
-        logits = logits.contiguous()
+        logits = logits_output.next_token_logits
 
         if self.use_nan_detectioin and torch.any(torch.isnan(logits)):
             logger.warning("Detected errors during sampling! NaN in the logits.")
@@ -47,6 +46,8 @@ class Sampler(nn.Module):
         if sampling_info.is_all_greedy:
             # Use torch.argmax if all requests use greedy sampling
             batch_next_token_ids = torch.argmax(logits, -1)
+            if return_logprob:
+                logprobs = torch.nn.functional.log_softmax(logits, dim=-1)
         else:
             # Post process logits
             logits.div_(sampling_info.temperatures)
@@ -54,6 +55,12 @@ class Sampler(nn.Module):
             del logits
 
             if global_server_args_dict["sampling_backend"] == "flashinfer":
+                if return_logprob:
+                    # NOTE: the top_p_renorm_prob from flashinfer has numerical problems
+                    logprobs = torch.log(
+                        top_p_normalize_probs_torch(probs, sampling_info.top_ps)
+                    )
+
                 max_top_k_round, batch_size = 32, probs.shape[0]
                 uniform_samples = torch.rand(
                     (max_top_k_round, batch_size), device=probs.device
@@ -76,6 +83,7 @@ class Sampler(nn.Module):
                 if self.use_nan_detectioin and not torch.all(success):
                     logger.warning("Detected errors during sampling!")
                     batch_next_token_ids = torch.zeros_like(batch_next_token_ids)
+
             elif global_server_args_dict["sampling_backend"] == "pytorch":
                 # A slower fallback implementation with torch native operations.
                 batch_next_token_ids = top_k_top_p_min_p_sampling_from_probs_torch(
@@ -85,12 +93,31 @@ class Sampler(nn.Module):
                     sampling_info.min_ps,
                     sampling_info.need_min_p_sampling,
                 )
+                if return_logprob:
+                    logprobs = torch.log(
+                        top_p_normalize_probs_torch(probs, sampling_info.top_ps)
+                    )
             else:
                 raise ValueError(
                     f"Invalid sampling backend: {global_server_args_dict['sampling_backend']}"
                 )
 
-        return batch_next_token_ids.to(torch.int32)
+        batch_next_token_ids = batch_next_token_ids.to(torch.int32)
+
+        # Attach logprobs to logits_output (in-place modification)
+        if return_logprob:
+            if any(x > 0 for x in top_logprobs_nums):
+                (
+                    logits_output.next_token_top_logprobs_val,
+                    logits_output.next_token_top_logprobs_idx,
+                ) = get_top_logprobs(logprobs, top_logprobs_nums)
+
+            logits_output.next_token_logprobs = logprobs[
+                torch.arange(len(batch_next_token_ids), device=sampling_info.device),
+                batch_next_token_ids,
+            ]
+
+        return batch_next_token_ids
 
 
 def top_k_top_p_min_p_sampling_from_probs_torch(
@@ -120,20 +147,27 @@ def top_k_top_p_min_p_sampling_from_probs_torch(
     return batch_next_token_ids
 
 
-def top_p_normalize_probs(
+def top_p_normalize_probs_torch(
     probs: torch.Tensor,
     top_ps: torch.Tensor,
 ):
-    if global_server_args_dict["sampling_backend"] == "flashinfer":
-        return top_p_renorm_prob(probs, top_ps)
-    elif global_server_args_dict["sampling_backend"] == "pytorch":
     # See also top_k_top_p_min_p_sampling_from_probs_torch
     probs_sort, probs_idx = probs.sort(dim=-1, descending=True)
     probs_sum = torch.cumsum(probs_sort, dim=-1)
     probs_sort[(probs_sum - probs_sort) > top_ps.view(-1, 1)] = 0.0
     probs_sort.div_(probs_sort.sum(dim=-1, keepdim=True))
     return torch.zeros_like(probs_sort).scatter_(-1, probs_idx, probs_sort)
-    else:
-        raise ValueError(
-            f"Invalid sampling backend: {global_server_args_dict['sampling_backend']}"
-        )
+
+
+def get_top_logprobs(logprobs: torch.Tensor, top_logprobs_nums: List[int]):
+    max_k = max(top_logprobs_nums)
+    ret = logprobs.topk(max_k, dim=1)
+    values = ret.values.tolist()
+    indices = ret.indices.tolist()
+
+    output_top_logprobs_val = []
+    output_top_logprobs_idx = []
+    for i, k in enumerate(top_logprobs_nums):
+        output_top_logprobs_val.append(values[i][:k])
+        output_top_logprobs_idx.append(indices[i][:k])
+    return output_top_logprobs_val, output_top_logprobs_idx

python/sglang/srt/managers/scheduler.py

@@ -974,12 +974,10 @@ class Scheduler:
                 logits_output, next_token_ids = self.tp_worker.resolve_batch_result(bid)
             else:
                 # Move next_token_ids and logprobs to cpu
+                next_token_ids = next_token_ids.tolist()
                 if batch.return_logprob:
                     logits_output.next_token_logprobs = (
-                        logits_output.next_token_logprobs[
-                            torch.arange(len(next_token_ids), device=self.device),
-                            next_token_ids,
-                        ].tolist()
+                        logits_output.next_token_logprobs.tolist()
                     )
                     logits_output.input_token_logprobs = (
                         logits_output.input_token_logprobs.tolist()
@@ -987,7 +985,6 @@ class Scheduler:
                     logits_output.normalized_prompt_logprobs = (
                         logits_output.normalized_prompt_logprobs.tolist()
                     )
-                next_token_ids = next_token_ids.tolist()
 
             # Check finish conditions
             logprob_pt = 0
@@ -1064,13 +1061,9 @@ class Scheduler:
             logits_output, next_token_ids = self.tp_worker.resolve_batch_result(bid)
             next_token_logprobs = logits_output.next_token_logprobs
         else:
-            # Move next_token_ids and logprobs to cpu
-            if batch.return_logprob:
-                next_token_logprobs = logits_output.next_token_logprobs[
-                    torch.arange(len(next_token_ids), device=self.device),
-                    next_token_ids,
-                ].tolist()
             next_token_ids = next_token_ids.tolist()
+            if batch.return_logprob:
+                next_token_logprobs = logits_output.next_token_logprobs.tolist()
 
         self.token_to_kv_pool.free_group_begin()
 
@@ -1095,10 +1088,10 @@ class Scheduler:
                 req.output_token_logprobs_idx.append(next_token_id)
                 if req.top_logprobs_num > 0:
                     req.output_top_logprobs_val.append(
-                        logits_output.output_top_logprobs_val[i]
+                        logits_output.next_token_top_logprobs_val[i]
                     )
                     req.output_top_logprobs_idx.append(
-                        logits_output.output_top_logprobs_idx[i]
+                        logits_output.next_token_top_logprobs_idx[i]
                     )
 
             if req.grammar is not None:
@@ -1200,8 +1193,9 @@ class Scheduler:
                 req.output_top_logprobs_idx.extend(
                     output.input_top_logprobs_idx[i][-req.last_update_decode_tokens :]
                 )
-            req.output_top_logprobs_val.append(output.output_top_logprobs_val[i])
-            req.output_top_logprobs_idx.append(output.output_top_logprobs_idx[i])
+
+            req.output_top_logprobs_val.append(output.next_token_top_logprobs_val[i])
+            req.output_top_logprobs_idx.append(output.next_token_top_logprobs_idx[i])
 
         return num_input_logprobs
 

python/sglang/srt/managers/tp_worker_overlap_thread.py

@@ -144,10 +144,9 @@ class TpModelWorkerClient:
 
             # Copy results to the CPU
             if model_worker_batch.return_logprob:
-                logits_output.next_token_logprobs = logits_output.next_token_logprobs[
-                    torch.arange(len(next_token_ids), device=self.device),
-                    next_token_ids,
-                ].to("cpu", non_blocking=True)
+                logits_output.next_token_logprobs = (
+                    logits_output.next_token_logprobs.to("cpu", non_blocking=True)
+                )
                 if logits_output.input_token_logprobs is not None:
                     logits_output.input_token_logprobs = (
                         logits_output.input_token_logprobs.to("cpu", non_blocking=True)

python/sglang/srt/model_executor/cuda_graph_runner.py

@@ -392,34 +392,7 @@ class CudaGraphRunner:
         self.graphs[bs].replay()
         next_token_logits = self.output_buffers[bs][:raw_bs]
 
-        # Extract logprobs
-        if forward_batch.return_logprob:
-            logits_metadata = LogitsMetadata(
-                forward_mode=ForwardMode.DECODE,
-                top_logprobs_nums=forward_batch.top_logprobs_nums,
-            )
-            next_token_logprobs = (
-                LogitsProcessor.compute_temp_top_p_normalized_logprobs(
-                    next_token_logits, logits_metadata
-                )
-            )
         logits_output = LogitsProcessorOutput(
             next_token_logits=next_token_logits,
-                next_token_logprobs=next_token_logprobs,
         )
-            return_top_logprob = any(x > 0 for x in forward_batch.top_logprobs_nums)
-            if return_top_logprob:
-                (
-                    logits_output.output_top_logprobs_val,
-                    logits_output.output_top_logprobs_idx,
-                ) = LogitsProcessor.get_top_logprobs(
-                    next_token_logprobs, logits_metadata
-                )[
-                    2:4
-                ]
-        else:
-            logits_output = LogitsProcessorOutput(
-                next_token_logits=next_token_logits,
-            )
-
         return logits_output

python/sglang/srt/model_executor/model_runner.py

@@ -36,7 +36,7 @@ from sglang.srt.layers.attention.flashinfer_backend import FlashInferAttnBackend
 from sglang.srt.layers.attention.torch_native_backend import TorchNativeAttnBackend
 from sglang.srt.layers.attention.triton_backend import TritonAttnBackend
 from sglang.srt.layers.logits_processor import LogitsProcessorOutput
-from sglang.srt.layers.sampler import Sampler
+from sglang.srt.layers.sampler import Sampler, get_top_logprobs
 from sglang.srt.layers.torchao_utils import apply_torchao_config_to_model
 from sglang.srt.lora.lora_manager import LoRAManager
 from sglang.srt.managers.schedule_batch import global_server_args_dict
@@ -48,7 +48,6 @@ from sglang.srt.mem_cache.memory_pool import (
 )
 from sglang.srt.model_executor.forward_batch_info import ForwardBatch
 from sglang.srt.model_loader import get_model
-from sglang.srt.sampling.sampling_batch_info import SamplingBatchInfo
 from sglang.srt.server_args import ServerArgs
 from sglang.srt.utils import (
     enable_show_time_cost,
@@ -192,7 +191,8 @@ class ModelRunner:
         torch.get_device_module(self.device).set_device(self.gpu_id)
         if self.device == "cuda":
             backend = "nccl"
-        # ToDO(liangan1):Just use gloo to bypass the initilization fail
+
+        # TODO(liangan1):Just use gloo to bypass the initilization fail
         # Need to use xccl for xpu backend in the future
         elif self.device == "xpu":
             backend = "gloo"
@@ -704,6 +704,7 @@ class ModelRunner:
     def sample(
         self, logits_output: LogitsProcessorOutput, forward_batch: ForwardBatch
     ) -> torch.Tensor:
+        # Apply logit bias
         sampling_info = forward_batch.sampling_info
         if sampling_info.sampling_info_done:
             # Overlap mode: the function update_regex_vocab_mask was executed
@@ -714,34 +715,16 @@ class ModelRunner:
             # Normal mode: Put CPU-heavy tasks here. They will be overlapped with the forward pass.
             sampling_info.update_regex_vocab_mask()
             sampling_info.update_penalties()
-        logits = self.apply_logits_bias(logits_output.next_token_logits, sampling_info)
-
-        # Sample the next tokens.
-        next_token_ids = self.sampler(logits, sampling_info)
-        return next_token_ids
-
-    def apply_logits_bias(self, logits: torch.Tensor, sampling_info: SamplingBatchInfo):
-        # Apply logit_bias
-        if sampling_info.logit_bias is not None:
-            logits.add_(sampling_info.logit_bias)
+        sampling_info.apply_logits_bias(logits_output.next_token_logits)
 
-        # min-token, presence, frequency
-        if sampling_info.linear_penalties is not None:
-            logits.add_(sampling_info.linear_penalties)
-
-        # repetition
-        if sampling_info.scaling_penalties is not None:
-            logits = torch.where(
-                logits > 0,
-                logits / sampling_info.scaling_penalties,
-                logits * sampling_info.scaling_penalties,
+        # Sample the next tokens
+        next_token_ids = self.sampler(
+            logits_output,
+            sampling_info,
+            forward_batch.return_logprob,
+            forward_batch.top_logprobs_nums,
         )
-
-        # Apply regex vocab_mask
-        if sampling_info.vocab_mask is not None:
-            sampling_info.apply_mask(logits=logits, vocab_mask=sampling_info.vocab_mask)
-
-        return logits
+        return next_token_ids
 
     @property
     def model_is_mrope(self) -> bool:

python/sglang/srt/sampling/sampling_batch_info.py

@@ -232,3 +232,26 @@ class SamplingBatchInfo:
         self.logit_bias = SamplingBatchInfo.merge_bias_tensor(
             self.logit_bias, other.logit_bias, len(self), len(other), self.device
         )
+
+    def apply_logits_bias(self, logits: torch.Tensor):
+        # Apply logit_bias
+        if self.logit_bias is not None:
+            logits.add_(self.logit_bias)
+
+        # min-token, presence, frequency
+        if self.linear_penalties is not None:
+            logits.add_(self.linear_penalties)
+
+        # repetition
+        if self.scaling_penalties is not None:
+            logits = torch.where(
+                logits > 0,
+                logits / self.scaling_penalties,
+                logits * self.scaling_penalties,
+            )
+
+        # Apply regex vocab_mask
+        if self.vocab_mask is not None:
+            self.apply_mask(logits=logits, vocab_mask=self.vocab_mask)
+
+        return logits

test/srt/sampling/penaltylib/test_srt_endpoint_with_penalizers.py

@@ -6,7 +6,7 @@ import requests
 
 from sglang.srt.utils import kill_process_tree
 from sglang.test.test_utils import (
-    DEFAULT_MODEL_NAME_FOR_TEST,
+    DEFAULT_SMALL_MODEL_NAME_FOR_TEST,
     DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
     DEFAULT_URL_FOR_TEST,
     popen_launch_server,
@@ -17,7 +17,7 @@ class TestBatchPenalizerE2E(unittest.TestCase):
 
     @classmethod
     def setUpClass(cls):
-        cls.model = DEFAULT_MODEL_NAME_FOR_TEST
+        cls.model = DEFAULT_SMALL_MODEL_NAME_FOR_TEST
         cls.base_url = DEFAULT_URL_FOR_TEST
         cls.process = popen_launch_server(
             cls.model,

test/srt/test_srt_endpoint.py

@@ -213,6 +213,41 @@ class TestSRTEndpoint(unittest.TestCase):
         max_diff = np.max(diff)
         self.assertLess(max_diff, 0.25)
 
+    def test_logprob_grammar(self):
+        prompts = "Question: Is Paris the Capital of France? Answer:"
+        allowed_tokens = [" Yes", " No"]
+
+        response = requests.post(
+            self.base_url + "/generate",
+            json={
+                "text": prompts,
+                "sampling_params": {
+                    "temperature": 1.0,
+                    "max_new_tokens": 1,
+                    "regex": "( Yes| No)",
+                },
+                "return_logprob": True,
+                "top_logprobs_num": 5,
+                "return_text_in_logprobs": True,
+            },
+        )
+        response_json = response.json()
+        output_top_logprobs = response_json["meta_info"]["output_top_logprobs"][0]
+        print(f"{output_top_logprobs=}")
+
+        # Parse results
+        # This is becaues the grammar constraint allows all prefix tokens
+        logprobs = [None] * 2
+        for i in range(len(output_top_logprobs)):
+            try:
+                idx = allowed_tokens.index(output_top_logprobs[i][2])
+            except ValueError:
+                # Not found
+                continue
+            logprobs[idx] = output_top_logprobs[i][0]
+
+        self.assertTrue(all(x is not None for x in logprobs))
+
     def test_get_server_info(self):
         response = requests.get(self.base_url + "/get_server_info")
         response_json = response.json()