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sglang/python/sglang/srt/layers/logits_processor.py
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# Copyright 2023-2024 SGLang Team
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
"""Logits processing."""
import dataclasses
import logging
from contextlib import contextmanager
from typing import Any, Dict, List, Optional, Tuple, Union
import torch
from torch import nn
from sglang.kernels.ops.activation.softcap import (
softcap_inplace_logits as fused_softcap,
)
from sglang.srt.distributed.device_communicators import triton_symm_mem_ag
from sglang.srt.layers.aux_hidden_states import (
AuxHiddenStates,
pack_aux_hidden_states,
)
from sglang.srt.layers.dp_attention import (
DpPaddingMode,
attn_tp_all_gather,
attn_tp_all_gather_into_tensor,
dp_gather_replicate,
dp_scatter,
get_dp_device,
get_dp_dtype,
get_dp_hidden_size,
)
from sglang.srt.layers.logprob_processor import (
InputLogprobProcessor,
LogprobStage,
get_token_ids_logprobs_raw,
get_top_logprobs_raw,
)
from sglang.srt.layers.vocab_parallel_embedding import VocabParallelEmbedding
from sglang.srt.model_executor.forward_batch_info import (
CaptureHiddenMode,
ForwardBatch,
ForwardMode,
)
from sglang.srt.runtime_context import get_exec, get_parallel
from sglang.srt.utils.common import (
is_cpu,
is_npu,
is_pin_memory_available,
use_intel_amx_backend,
)
logger = logging.getLogger(__name__)
_is_npu = is_npu()
_is_cpu = is_cpu()
_UNQUANTIZED_LM_HEAD_METHODS = {
"UnquantizedEmbeddingMethod",
"UnquantizedLinearMethod",
"PackWeightMethod",
}
# None outside a FlashInfer autotune pass; inside one, whether that pass runs the
# LM head. Not-None means the forward's output is discarded -- attention backends
# read that via get_in_autotune_dummy_run() to skip a cross-node exchange.
# Skipping the LM head skips its [batch * dp_size, vocab] all-gather, which OOMs
# under DP attention with a tight mem_fraction_static.
_autotune_run_lm_head: Optional[bool] = None
def get_in_autotune_dummy_run() -> bool:
return _autotune_run_lm_head is not None
@contextmanager
def autotune_dummy_run_mode(*, run_lm_head: bool):
global _autotune_run_lm_head
_autotune_run_lm_head = run_lm_head
try:
yield
finally:
_autotune_run_lm_head = None
@dataclasses.dataclass
class LogitsProcessorOutput:
## Part 1: This part will be assigned in python/sglang/srt/layers/logits_processor.py::LogitsProcessor
# The logits of the next tokens. shape: [#seq, vocab_size]
# Can be None for certain prefill-only requests (e.g., multi-item scoring) that don't need next token generation
next_token_logits: Optional[torch.Tensor]
# Used by speculative decoding (EAGLE)
# The last hidden layers
hidden_states: Optional[torch.Tensor] = None
## Part 2: This part will be assigned in python/sglang/srt/layers/sampler.py::Sampler
# he log probs of output tokens, if SGLANG_RETURN_ORIGINAL_LOGPROB = True, will get the log probs before applying temperature. If False, will get the log probs before applying temperature.
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
# The logprobs and ids of the requested token ids in output positions. shape: [#seq, n] (n is the number of requested token ids)
# Can contain either lists or GPU tensors (for delayed copy optimization in prefill-only requests)
next_token_token_ids_logprobs_val: Optional[
List[Union[List[float], torch.Tensor]]
] = None
next_token_token_ids_logprobs_idx: Optional[List] = None
# Sparse top-k/top-p/min-p support ids and selected-token logprob after
# truncation/renormalization. Only populated when requested.
next_token_sampling_mask_idx: Optional[List[Optional[List[int]]]] = None
next_token_sampling_logprobs: Optional[List[Optional[float]]] = None
## Part 3: Prefill-only. This part will be assigned in python/sglang/srt/layers/logits_processor.py::LogitsProcessor
# The logprobs of input tokens. shape: [#token]
input_token_logprobs: Optional[torch.Tensor] = None
# The logprobs and ids of the top-k tokens in input positions. shape: [#seq, #token, k]
input_top_logprobs_val: Optional[List] = None
input_top_logprobs_idx: Optional[List] = None
# The logprobs and ids of the requested token ids in input positions. shape: [#seq, n] (n is the number of requested token ids)
# Can contain either lists or GPU tensors (for delayed GPU-to-CPU transfer optimization)
input_token_ids_logprobs_val: Optional[List[Union[List[float], torch.Tensor]]] = (
None
)
input_token_ids_logprobs_idx: Optional[List] = None
## Part 4: Diffusion LLM only.
full_logits: Optional[torch.Tensor] = None
## Part 5: Customized Info
customized_info: Optional[Dict[str, List[Any]]] = None
## Part 6: Temporary variables
# FIXME: These fields are not logits-related but are passed through here as a
# workaround since ForwardBatch is local to forward_batch_generation().
# They should be moved to GenerationBatchResult to keep this class clean.
mm_input_embeds: Optional[torch.Tensor] = None
@dataclasses.dataclass
class LogitsMetadata:
forward_mode: ForwardMode
capture_hidden_mode: CaptureHiddenMode = CaptureHiddenMode.NULL
next_token_logits_buffer: Optional[torch.Tensor] = None
extend_return_logprob: bool = False
extend_return_top_logprob: bool = False
extend_token_ids_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
top_logprobs_nums: Optional[List[int]] = None
extend_input_logprob_token_ids_gpu: Optional[torch.Tensor] = None
token_ids_logprobs: Optional[List[List[int]]] = None
# logits and logprobs post processing
temperature: torch.Tensor = None
top_p: torch.Tensor = None
# DP attention metadata. Not needed when DP attention is not used.
# Number of tokens in the request.
global_num_tokens_gpu: Optional[torch.Tensor] = None
# The start position of local hidden states.
dp_local_start_pos: Optional[torch.Tensor] = None
dp_local_num_tokens: Optional[torch.Tensor] = None
global_dp_buffer_len: Optional[int] = None
# Number of tokens to sample per DP rank
global_num_tokens_for_logprob_cpu: Optional[torch.Tensor] = None
global_num_tokens_for_logprob_gpu: Optional[torch.Tensor] = None
# The gather mode for DP attention
dp_padding_mode: Optional[DpPaddingMode] = None
# Whether this batch is prefill-only (no token generation needed)
is_prefill_only: bool = False
mm_input_embeds: Optional[torch.Tensor] = None
# DRAFT_EXTEND_V2: when set, lm_head runs only on these rows (see
# EagleDraftExtendInput.select_index).
draft_extend_select_index: Optional[torch.Tensor] = None
@classmethod
def from_forward_batch(cls, forward_batch: ForwardBatch):
if (
forward_batch.forward_mode.is_extend()
and forward_batch.return_logprob
and not forward_batch.forward_mode.is_target_verify()
):
extend_return_top_logprob = any(
x > 0 for x in forward_batch.top_logprobs_nums
)
extend_token_ids_logprob = any(
x is not None for x in forward_batch.token_ids_logprobs
)
extend_return_logprob = False
extend_logprob_pruned_lens_cpu = []
for extend_len, start_len in zip(
forward_batch.extend_seq_lens_cpu,
forward_batch.extend_logprob_start_lens_cpu,
):
if extend_len - start_len > 0:
extend_return_logprob = True
extend_logprob_pruned_lens_cpu.append(extend_len - start_len)
else:
extend_return_logprob = extend_return_top_logprob = (
extend_token_ids_logprob
) = extend_logprob_pruned_lens_cpu = False
if forward_batch.forward_mode.is_draft_extend_v2():
draft_extend_select_index = forward_batch.spec_info.select_index
else:
draft_extend_select_index = None
return cls(
forward_mode=forward_batch.forward_mode,
capture_hidden_mode=forward_batch.capture_hidden_mode,
next_token_logits_buffer=forward_batch.next_token_logits_buffer,
extend_return_logprob=extend_return_logprob,
extend_return_top_logprob=extend_return_top_logprob,
extend_token_ids_logprob=extend_token_ids_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,
top_logprobs_nums=forward_batch.top_logprobs_nums,
token_ids_logprobs=forward_batch.token_ids_logprobs,
extend_input_logprob_token_ids_gpu=forward_batch.extend_input_logprob_token_ids_gpu,
is_prefill_only=forward_batch.is_prefill_only,
global_num_tokens_gpu=forward_batch.global_num_tokens_gpu,
dp_local_start_pos=forward_batch.dp_local_start_pos,
dp_local_num_tokens=forward_batch.dp_local_num_tokens,
global_dp_buffer_len=forward_batch.global_dp_buffer_len,
global_num_tokens_for_logprob_cpu=forward_batch.global_num_tokens_for_logprob_cpu,
global_num_tokens_for_logprob_gpu=forward_batch.global_num_tokens_for_logprob_gpu,
dp_padding_mode=DpPaddingMode.SUM_LEN,
mm_input_embeds=forward_batch.mm_input_embeds,
draft_extend_select_index=draft_extend_select_index,
)
def compute_dp_attention_metadata(self):
cumtokens = torch.cumsum(self.global_num_tokens_for_logprob_gpu, dim=0)
dp_rank = get_parallel().attn_dp_rank
if dp_rank == 0:
dp_local_start_pos = torch.zeros_like(
self.global_num_tokens_for_logprob_gpu[0]
)
else:
dp_local_start_pos = cumtokens[dp_rank - 1]
self.dp_local_start_pos = dp_local_start_pos
self.dp_local_num_tokens = self.global_num_tokens_for_logprob_gpu[dp_rank]
hidden_size = get_dp_hidden_size()
dtype = get_dp_dtype()
device = get_dp_device()
if self.global_num_tokens_for_logprob_cpu is not None:
# create a smaller buffer to reduce peak memory usage
self.global_dp_buffer_len = sum(self.global_num_tokens_for_logprob_cpu)
else:
self.global_dp_buffer_len = self.global_dp_buffer_len
self.gathered_buffer = torch.empty(
(
self.global_dp_buffer_len,
hidden_size,
),
dtype=dtype,
device=device,
)
class LogitsProcessor(nn.Module):
def __init__(
self,
config,
skip_all_gather: bool = False,
logit_scale: Optional[float] = None,
return_full_logits: bool = False,
):
super().__init__()
self.config = config
self.vocab_size = config.vocab_size
self.logit_scale = logit_scale
self.use_attn_tp_group = get_parallel().enable_dp_lm_head
self.use_fp32_lm_head = get_exec().features.enable_fp32_lm_head
if self.use_attn_tp_group:
self.attn_tp_size = get_parallel().attn_tp_size
self.do_tensor_parallel_all_gather = (
not skip_all_gather and self.attn_tp_size > 1
)
self.do_tensor_parallel_all_gather_dp_attn = False
else:
self.do_tensor_parallel_all_gather = (
not skip_all_gather and get_parallel().tp_size > 1
)
self.do_tensor_parallel_all_gather_dp_attn = (
self.do_tensor_parallel_all_gather and get_parallel().attn_dp_size != 1
)
self.final_logit_softcapping = getattr(
self.config, "final_logit_softcapping", None
)
if (
self.final_logit_softcapping is not None
and self.final_logit_softcapping < 0
):
self.final_logit_softcapping = None
self.return_full_logits = return_full_logits
self.enable_mis = get_exec().features.enable_mis
self.rl_on_policy_target = get_exec().deterministic.rl_on_policy_target
self._logits_gatherer = triton_symm_mem_ag.MultimemAllGatherer(
max_tokens=triton_symm_mem_ag.recommended_max_tokens(
include_prefill=False, floor=128
),
enabled=self.do_tensor_parallel_all_gather and not self.use_attn_tp_group,
skip_entry_sync=True,
)
self.input_logprob_processor = InputLogprobProcessor()
def forward(
self,
input_ids,
hidden_states,
lm_head: VocabParallelEmbedding,
logits_metadata: Union[LogitsMetadata, ForwardBatch],
aux_hidden_states: Optional[AuxHiddenStates] = None,
hidden_states_before_norm: Optional[torch.Tensor] = None,
) -> LogitsProcessorOutput:
# Extract MIS indices before ForwardBatch → LogitsMetadata conversion
multi_item_delimiter_indices = None
if isinstance(logits_metadata, ForwardBatch):
multi_item_delimiter_indices = logits_metadata.multi_item_delimiter_indices
logits_metadata = LogitsMetadata.from_forward_batch(logits_metadata)
# Autotune dummy run discards this output. `is False` not `not`: None
# means no autotune pass, which must not skip. Placed before the MIS /
# DLLM / common dispatch so all three LM-head paths are skipped.
if _autotune_run_lm_head is False:
return LogitsProcessorOutput(next_token_logits=None)
# Multi-item scoring only for prefill-only requests with pre-computed indices.
if multi_item_delimiter_indices is not None and logits_metadata.is_prefill_only:
return self.compute_logprobs_for_multi_item_scoring(
input_ids,
hidden_states,
lm_head,
logits_metadata,
multi_item_delimiter_indices,
)
# Diffusion LLM only.
if logits_metadata.forward_mode.is_dllm_extend():
return self._get_dllm_logits(hidden_states, lm_head, logits_metadata)
# Get the last hidden states and last logits for the next token prediction
(
pruned_states,
pruned_states_before_norm,
aux_pruned_states,
sample_indices,
input_logprob_indices,
token_to_seq_idx,
) = self._get_pruned_states(
hidden_states,
hidden_states_before_norm,
aux_hidden_states,
logits_metadata,
)
hidden_states_to_store = self._get_hidden_states_to_store(
hidden_states,
hidden_states_before_norm,
aux_hidden_states,
pruned_states,
pruned_states_before_norm,
aux_pruned_states,
sample_indices,
logits_metadata,
)
del hidden_states
if not logits_metadata.extend_return_logprob:
# Compute logits for both input and sampled tokens.
logits = self._get_logits(pruned_states, lm_head, logits_metadata)
sampled_logits = (
logits[sample_indices] if sample_indices is not None else logits
)
# Decode mode or extend mode without return_logprob.
return LogitsProcessorOutput(
next_token_logits=sampled_logits,
hidden_states=hidden_states_to_store,
mm_input_embeds=logits_metadata.mm_input_embeds,
)
logprobs_result, sampled_logits = self.input_logprob_processor.forward(
pruned_states=pruned_states,
sample_indices=sample_indices,
input_logprob_indices=input_logprob_indices,
token_to_seq_idx=token_to_seq_idx,
lm_head=lm_head,
get_logits_fn=self._get_logits,
logits_metadata=logits_metadata,
skip_chunking_for_dp_attn=self.do_tensor_parallel_all_gather_dp_attn,
)
logits_output = LogitsProcessorOutput(
next_token_logits=sampled_logits,
hidden_states=hidden_states_to_store,
mm_input_embeds=logits_metadata.mm_input_embeds,
)
logprobs_result.write_input_to(logits_output)
return logits_output
def _get_pruned_states(
self,
hidden_states: torch.Tensor,
hidden_states_before_norm: Optional[torch.Tensor],
aux_hidden_states: Optional[AuxHiddenStates],
logits_metadata: LogitsMetadata,
):
pruned_states_before_norm: Optional[torch.Tensor] = None
aux_pruned_states = None
token_to_seq_idx = []
if (
logits_metadata.forward_mode.is_decode_or_idle()
or logits_metadata.forward_mode.is_target_verify()
or logits_metadata.forward_mode.is_draft_extend_v2()
):
if logits_metadata.draft_extend_select_index is not None:
# Only next_token_logits narrows to [bs, vocab]; the
# FULL-capture hidden stays unpruned.
pruned_states = hidden_states[logits_metadata.draft_extend_select_index]
else:
pruned_states = hidden_states
pruned_states_before_norm = hidden_states_before_norm
if aux_hidden_states is not None:
aux_pruned_states = (
aux_hidden_states
if isinstance(aux_hidden_states, torch.Tensor)
else [hidden for hidden in aux_hidden_states]
)
sample_indices = None
input_logprob_indices = None
elif (
logits_metadata.forward_mode.is_extend()
and not logits_metadata.extend_return_logprob
):
# Prefill without input logprobs.
last_index = torch.cumsum(logits_metadata.extend_seq_lens, dim=0) - 1
pruned_states = hidden_states[last_index]
if hidden_states_before_norm is not None:
pruned_states_before_norm = hidden_states_before_norm[last_index]
if aux_hidden_states is not None:
aux_pruned_states = (
aux_hidden_states[last_index]
if isinstance(aux_hidden_states, torch.Tensor)
else [hidden[last_index] for hidden in aux_hidden_states]
)
sample_indices = None
input_logprob_indices = None
else:
# Prefill with input logprobs.
# Find 4 different indices.
# 1. pruned_states: hidden states that we want logprobs from.
# 2. sample_indices: Indices that have sampled tokens.
# 3. input_logprob_indices: Indices that have input logprob tokens.
# 4. token_to_seq_idx: map each token to its sequence index
#
# Example
# -------
# Suppose a batch (flattened by sequence):
# [t00, t01, t02, t03, t10, t11, t12, t13, t14, t20, t21, t22, t23, t24, t25]
# extend_seq_lens_cpu = [4, 5, 6]
# extend_logprob_start_lens_cpu = [0, 5, 3]
#
# Then, the indices are:
# pruned_states -> [t00, t01, t02, t03, t14, t23, t24, t25]
# sample_indices -> [3, 4, 7]
# input_logprob_indices -> [0, 1, 2, 3, 5, 6, 7]
# token_to_seq_idx -> [0, 0, 0, 0, 1, 2, 2, 2]
#
# If chunk is enabled and chunk_size = 3, the chunks will be computed in a chunked manner:
# [t00, t01, t02], [t03, t14, t23], [t24, t25]
sample_index_pt = -1
sample_indices = []
input_logprob_indices_pt = 0
input_logprob_indices = []
pt, pruned_states_list, pruned_states_before_norm_list = 0, [], []
is_packed_aux_hidden_states = isinstance(aux_hidden_states, torch.Tensor)
aux_pruned_states_lists = None
if aux_hidden_states is not None:
aux_pruned_states_lists = (
[]
if is_packed_aux_hidden_states
else [[] for _ in aux_hidden_states]
)
for idx, (extend_logprob_start_len, extend_len) in enumerate(
zip(
logits_metadata.extend_logprob_start_lens_cpu,
logits_metadata.extend_seq_lens_cpu,
)
):
# It can happen in chunked prefill. We still need to sample 1 token,
# But we don't want to include it in input logprob.
if extend_len == extend_logprob_start_len:
start_len = extend_logprob_start_len - 1
else:
start_len = extend_logprob_start_len
# We always need at least 1 token to sample because that's required
# by a caller.
assert extend_len > start_len
pruned_states_list.append(
hidden_states[pt + start_len : pt + extend_len]
)
if hidden_states_before_norm is not None:
pruned_states_before_norm_list.append(
hidden_states_before_norm[pt + start_len : pt + extend_len]
)
if aux_pruned_states_lists is not None:
if is_packed_aux_hidden_states:
aux_pruned_states_lists.append(
aux_hidden_states[pt + start_len : pt + extend_len]
)
else:
for j, hidden in enumerate(aux_hidden_states):
aux_pruned_states_lists[j].append(
hidden[pt + start_len : pt + extend_len]
)
# Map each token to its sequence index, for chunked computation
# of input logprobs
token_to_seq_idx.extend([idx] * (extend_len - start_len))
pt += extend_len
sample_index_pt += extend_len - start_len
sample_indices.append(sample_index_pt)
input_logprob_indices.extend(
[
input_logprob_indices_pt + i
for i in range(extend_len - extend_logprob_start_len)
]
)
input_logprob_indices_pt += extend_len - start_len
pruned_states = torch.cat(pruned_states_list)
if hidden_states_before_norm is not None:
pruned_states_before_norm = torch.cat(pruned_states_before_norm_list)
if aux_pruned_states_lists is not None:
aux_pruned_states = (
torch.cat(aux_pruned_states_lists)
if is_packed_aux_hidden_states
else [torch.cat(lst) for lst in aux_pruned_states_lists]
)
# Build the index tensors via pinned host memory + non-blocking H2D
# so the small copy doesn't drain the stream.
sample_indices = torch.tensor(
sample_indices,
dtype=torch.int64,
pin_memory=is_pin_memory_available(),
).to(pruned_states.device, non_blocking=True)
input_logprob_indices = torch.tensor(
input_logprob_indices,
dtype=torch.int64,
pin_memory=is_pin_memory_available(),
).to(pruned_states.device, non_blocking=True)
return (
pruned_states,
pruned_states_before_norm,
aux_pruned_states,
sample_indices,
input_logprob_indices,
token_to_seq_idx,
)
def _get_hidden_states_to_store(
self,
hidden_states: torch.Tensor,
hidden_states_before_norm: Optional[torch.Tensor],
aux_hidden_states: Optional[AuxHiddenStates],
pruned_states: torch.Tensor,
pruned_states_before_norm: Optional[torch.Tensor],
aux_pruned_states: Optional[AuxHiddenStates],
sample_indices: Optional[torch.Tensor],
logits_metadata: LogitsMetadata,
) -> Optional[torch.Tensor]:
hidden_states_to_store: Optional[torch.Tensor] = None
hidden_states_to_store_before_norm: Optional[torch.Tensor] = None
if logits_metadata.capture_hidden_mode.need_capture():
if logits_metadata.capture_hidden_mode.is_full():
if aux_hidden_states is not None:
hidden_states_to_store = pack_aux_hidden_states(aux_hidden_states)
else:
hidden_states_to_store = hidden_states
hidden_states_to_store_before_norm = hidden_states_before_norm
elif logits_metadata.capture_hidden_mode.is_last():
# Get the last token hidden states. If sample_indices is None,
# pruned states only contain the last tokens already.
if aux_hidden_states is not None:
assert aux_pruned_states is not None
aux_pruned_states = pack_aux_hidden_states(aux_pruned_states)
hidden_states_to_store = (
aux_pruned_states[sample_indices]
if sample_indices is not None
else aux_pruned_states
)
else:
hidden_states_to_store = (
pruned_states[sample_indices]
if sample_indices is not None
else pruned_states
)
if hidden_states_before_norm is not None:
hidden_states_to_store_before_norm = (
pruned_states_before_norm[sample_indices]
if sample_indices is not None
else pruned_states_before_norm
)
else:
assert False, "Should never reach"
if hidden_states_to_store_before_norm is not None:
# NOTE: when hidden_states_before_norm is provided, we always
# prefer to return it.
hidden_states_to_store = hidden_states_to_store_before_norm
return hidden_states_to_store
def _get_logits(
self,
hidden_states: torch.Tensor,
lm_head: VocabParallelEmbedding,
logits_metadata: LogitsMetadata,
embedding_bias: Optional[torch.Tensor] = None,
use_logits_buffer: bool = True,
) -> torch.Tensor:
"""Get logits from hidden_states.
If sampled_logits_only is True, it means hidden_states only contain the
last position (e.g., extend without input logprobs). The caller should
guarantee the given hidden_states follow this constraint.
"""
hidden_states, local_hidden_states = self._gather_dp_attn_hidden_states(
hidden_states, logits_metadata
)
logits = self._compute_lm_head(hidden_states, lm_head, embedding_bias)
if self.logit_scale is not None:
logits.mul_(self.logit_scale)
if self.do_tensor_parallel_all_gather:
if self.use_attn_tp_group:
logits = self._gather_attn_tp_logits(logits)
else:
logits = self._logits_gatherer(logits)
logits = self._scatter_dp_attn_logits(
logits, local_hidden_states, logits_metadata
)
logits = self._copy_logits_to_buffer(
logits, logits_metadata, use_buffer=use_logits_buffer
)
if self.final_logit_softcapping:
if not (_is_npu or _is_cpu):
fused_softcap(logits, self.final_logit_softcapping)
else:
logits = self.final_logit_softcapping * torch.tanh(
logits / self.final_logit_softcapping
)
return logits
def _compute_lm_head(
self,
hidden_states: torch.Tensor,
lm_head: VocabParallelEmbedding,
embedding_bias: Optional[torch.Tensor] = None,
) -> torch.Tensor:
quant_method = getattr(lm_head, "quant_method", None)
if hasattr(lm_head, "set_lora") and hasattr(lm_head, "apply_lora"):
# This is a LoRA-wrapped module, use its forward method
logits = lm_head(hidden_states)
elif should_apply_lm_head_quant_method(lm_head, quant_method):
logits = quant_method.apply(lm_head, hidden_states, embedding_bias)
elif hasattr(lm_head, "weight"):
# Normal linear layer
if self.use_fp32_lm_head:
logits = torch.matmul(
hidden_states.to(torch.float32), lm_head.weight.to(torch.float32).T
)
elif use_intel_amx_backend(lm_head):
logits = torch.ops.sgl_kernel.weight_packed_linear(
hidden_states.to(lm_head.weight.dtype),
lm_head.weight,
None, # bias
True, # is_vnni
)
elif self.rl_on_policy_target is not None:
# Due to tie-weight, we may not be able to change lm_head's weight dtype
logits = torch.matmul(
hidden_states.bfloat16(), lm_head.weight.T.bfloat16()
)
else:
logits = torch.matmul(
hidden_states.to(lm_head.weight.dtype), lm_head.weight.T
)
else:
# GGUF models
# TODO: use weight_packed_linear for GGUF models
if self.use_fp32_lm_head:
with torch.cuda.amp.autocast(enabled=False):
logits = lm_head.quant_method.apply(
lm_head, hidden_states.to(torch.float32), embedding_bias
)
else:
logits = lm_head.quant_method.apply(
lm_head, hidden_states, embedding_bias
)
return logits
def _gather_dp_attn_hidden_states(
self, hidden_states: torch.Tensor, logits_metadata: LogitsMetadata
) -> Tuple[torch.Tensor, torch.Tensor]:
if self.do_tensor_parallel_all_gather_dp_attn:
logits_metadata.compute_dp_attention_metadata()
local_hidden_states = hidden_states
hidden_states = logits_metadata.gathered_buffer
dp_gather_replicate(hidden_states, local_hidden_states, logits_metadata)
return hidden_states, local_hidden_states
return hidden_states, hidden_states
def _gather_attn_tp_logits(self, logits: torch.Tensor) -> torch.Tensor:
if self.vocab_size % self.attn_tp_size == 0:
global_logits = torch.empty(
(
self.attn_tp_size,
logits.shape[0],
self.vocab_size // self.attn_tp_size,
),
device=logits.device,
dtype=logits.dtype,
)
attn_tp_all_gather_into_tensor(global_logits, logits)
global_logits = global_logits.permute(1, 0, 2).reshape(
logits.shape[0], self.vocab_size
)
else:
global_logits = torch.empty(
(self.vocab_size, logits.shape[0]),
device=logits.device,
dtype=logits.dtype,
)
global_logits = global_logits.T
attn_tp_all_gather(
list(global_logits.tensor_split(self.attn_tp_size, dim=-1)),
logits,
)
return global_logits
def _scatter_dp_attn_logits(
self,
logits: torch.Tensor,
local_hidden_states: torch.Tensor,
logits_metadata: LogitsMetadata,
) -> torch.Tensor:
if self.do_tensor_parallel_all_gather_dp_attn:
global_logits = logits
logits = torch.empty(
(local_hidden_states.shape[0], global_logits.shape[1]),
device=global_logits.device,
dtype=global_logits.dtype,
)
dp_scatter(logits, global_logits, logits_metadata)
return logits
def _copy_logits_to_buffer(
self,
logits: torch.Tensor,
logits_metadata: LogitsMetadata,
use_buffer: bool = True,
) -> torch.Tensor:
logits_buffer = logits_metadata.next_token_logits_buffer if use_buffer else None
if logits.shape[-1] > self.vocab_size:
logits = logits[:, : self.vocab_size]
logits_width = logits.shape[-1]
# The shared logits buffer is keyed by vocab width and rows; skip it
# when this batch has a different logits shape than the graph buffer.
if logits_buffer is not None and tuple(logits_buffer.shape) == tuple(
logits.shape
):
assert logits_buffer.dtype == torch.float
logits_buffer.copy_(logits)
logits = logits_buffer
else:
logits = logits.float()
return logits
def _get_dllm_logits(
self,
hidden_states: torch.Tensor,
lm_head: VocabParallelEmbedding,
logits_metadata: LogitsMetadata,
) -> LogitsProcessorOutput:
assert self.return_full_logits
full_logits = self._get_logits(hidden_states, lm_head, logits_metadata)
return LogitsProcessorOutput(
full_logits=full_logits,
next_token_logits=None,
)
def compute_logprobs_for_multi_item_scoring(
self,
input_ids,
hidden_states,
lm_head: VocabParallelEmbedding,
logits_metadata: Union[LogitsMetadata, ForwardBatch],
multi_item_delimiter_indices: List[torch.Tensor],
):
"""
Compute logprobs for multi-item scoring using pre-computed delimiter indices.
Sequence format: Query<delimiter>Item1<delimiter>Item2<delimiter>...
Scoring positions: Extracts logprobs at positions before each <delimiter>
Args:
input_ids: Input token IDs. Shape: [total_sequence_length].
hidden_states: Hidden states from the model. Shape: [sequence_length, hidden_dim].
lm_head: Language model head for computing logits.
logits_metadata: Metadata containing batch info and logprob specs.
multi_item_delimiter_indices: Pre-computed delimiter positions per request (CPU tensors).
"""
# Compute positions just before each delimiter.
# Build offset-adjusted indices on CPU, then do a single CPU→GPU transfer.
device = input_ids.device
all_tensors = []
if logits_metadata.extend_seq_lens_cpu is not None:
offset = 0
for req_seq_len, indices_tensor in zip(
logits_metadata.extend_seq_lens_cpu, multi_item_delimiter_indices
):
if len(indices_tensor) > 0:
# Note: if the first delimiter is at position 0 (empty query),
# indices - 1 wraps to -1. This is harmless — the first
# delimiter entry is always discarded by
# _process_multi_item_scoring_results.
all_tensors.append(indices_tensor + (offset - 1))
offset += req_seq_len
else:
all_tensors.append(multi_item_delimiter_indices[0] - 1)
multi_item_indices = torch.cat(all_tensors).to(device, non_blocking=True)
# Extract hidden states at delimiter positions for multi-item scoring
sliced_hidden = hidden_states[multi_item_indices]
sliced_logits = self._get_logits(sliced_hidden, lm_head, logits_metadata)
sliced_logprobs = torch.nn.functional.log_softmax(sliced_logits, dim=-1)
# Initialize return values
input_token_ids_logprobs_val = []
input_token_ids_logprobs_idx = []
input_top_logprobs_val = None
input_top_logprobs_idx = None
# Recalculate extend_logprob_pruned_lens_cpu to match delimiter counts per request
if (
logits_metadata.token_ids_logprobs
or logits_metadata.extend_return_top_logprob
):
logits_metadata.extend_logprob_pruned_lens_cpu = [
len(t) for t in multi_item_delimiter_indices
]
# Get the logprobs of specified token ids
if logits_metadata.extend_token_ids_logprob:
(
input_token_ids_logprobs_val,
input_token_ids_logprobs_idx,
) = get_token_ids_logprobs_raw(
sliced_logprobs,
logits_metadata.token_ids_logprobs,
stage=LogprobStage.PREFILL,
extend_logprob_pruned_lens_cpu=logits_metadata.extend_logprob_pruned_lens_cpu,
no_copy_to_cpu=True,
)
# Get the logprob of top-k tokens
if logits_metadata.extend_return_top_logprob:
(
input_top_logprobs_val,
input_top_logprobs_idx,
) = get_top_logprobs_raw(
sliced_logprobs,
logits_metadata.top_logprobs_nums,
stage=LogprobStage.PREFILL,
extend_logprob_pruned_lens_cpu=logits_metadata.extend_logprob_pruned_lens_cpu,
)
# MIS scores come from input_token_ids_logprobs_val (label-token logprobs),
# not from per-position input_token_logprobs. However, the shared logprob
# pipeline (add_input_logprob_return_values) asserts input_token_logprobs is
# non-None, converts it to a tuple, slices it, and validates its length —
# all before score_request() ever sees the result. We can't set it to None
# without changing those shared asserts, so we fill with zeros to satisfy
# the pipeline. score_request() ignores this field entirely.
input_token_logprobs = torch.zeros(multi_item_indices.shape[0], device=device)
return LogitsProcessorOutput(
next_token_logits=None,
input_token_logprobs=input_token_logprobs,
input_top_logprobs_val=input_top_logprobs_val,
input_top_logprobs_idx=input_top_logprobs_idx,
input_token_ids_logprobs_val=input_token_ids_logprobs_val,
input_token_ids_logprobs_idx=input_token_ids_logprobs_idx,
mm_input_embeds=logits_metadata.mm_input_embeds,
)
def _has_lm_head_runtime_attrs(lm_head, attr_names: Tuple[str, ...]) -> bool:
return all(hasattr(lm_head, attr_name) for attr_name in attr_names)
def should_apply_lm_head_quant_method(lm_head, quant_method) -> bool:
if (
quant_method is None
or not hasattr(lm_head, "weight")
or not callable(getattr(quant_method, "apply", None))
):
return False
method_name = type(quant_method).__name__
if method_name in _UNQUANTIZED_LM_HEAD_METHODS:
return False
# Some draft models share an unquantized target lm_head tensor while still
# carrying the draft model's stale ModelOpt quant_method. Only use the
# ModelOpt lm_head kernel when the runtime quantization state matches it.
if method_name == "ModelOptFp4LinearMethod":
if lm_head.weight.dtype == torch.int32 and _has_lm_head_runtime_attrs(
lm_head,
(
"weight_scale",
"weight_global_scale",
"workspace",
"input_size_per_partition",
"output_size_per_partition",
),
):
return True
return lm_head.weight.dtype == torch.uint8 and _has_lm_head_runtime_attrs(
lm_head,
(
"weight_scale_interleaved",
"alpha",
"input_scale_inv",
"input_size_per_partition",
"output_size_per_partition",
),
)
if method_name == "ModelOptNvFp4A16LinearMethod":
return lm_head.weight.dtype == torch.int32 and _has_lm_head_runtime_attrs(
lm_head,
(
"weight_scale",
"weight_global_scale",
"workspace",
"input_size_per_partition",
"output_size_per_partition",
),
)
if method_name == "ModelOptFp8LinearMethod":
return (
lm_head.weight.dtype == torch.float8_e4m3fn
and _has_lm_head_runtime_attrs(lm_head, ("weight_scale", "input_scale"))
)
return True