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sglang/python/sglang/srt/speculative/multi_layer_eagle_worker.py

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Python

# 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.
# ==============================================================================
import logging
import time
from typing import TYPE_CHECKING, List, Optional, Tuple
import torch
from sglang.srt.distributed import get_tp_group
from sglang.srt.layers.dp_attention import get_attention_tp_group
from sglang.srt.layers.logits_processor import LogitsProcessorOutput
from sglang.srt.layers.moe.utils import speculative_moe_backend_context
from sglang.srt.layers.utils.logprob import add_output_logprobs_for_spec_v1
from sglang.srt.managers.schedule_batch import ScheduleBatch
from sglang.srt.managers.scheduler import GenerationBatchResult
from sglang.srt.managers.tp_worker import TpModelWorker
from sglang.srt.model_executor.forward_batch_info import (
CaptureHiddenMode,
ForwardBatch,
ForwardMode,
)
from sglang.srt.server_args import ServerArgs
from sglang.srt.speculative.draft_utils import DraftBackendFactory
from sglang.srt.speculative.eagle_info import (
EagleDraftInput,
EagleVerifyInput,
EagleVerifyOutput,
)
from sglang.srt.speculative.eagle_utils import (
build_tree_kernel_efficient,
organize_draft_results,
)
from sglang.srt.speculative.multi_layer_eagle_draft_extend_cuda_graph_runner import (
MultiLayerEagleDraftExtendCudaGraphRunner,
)
from sglang.srt.speculative.spec_info import SpeculativeAlgorithm
from sglang.srt.speculative.spec_utils import (
draft_tp_context,
fast_topk,
generate_token_bitmask,
load_token_map,
maybe_detect_nan,
select_top_k_tokens,
)
from sglang.srt.utils import empty_context, get_available_gpu_memory, is_cuda, is_npu
if TYPE_CHECKING:
from sglang.srt.model_executor.model_runner import ModelRunner
_is_npu = is_npu()
if is_cuda():
from sgl_kernel import segment_packbits # noqa: F401
logger = logging.getLogger(__name__)
class MultiLayerEagleWorker(TpModelWorker):
def __init__(
self,
server_args: ServerArgs,
gpu_id: int,
tp_rank: int,
dp_rank: Optional[int],
moe_ep_rank: int,
attn_cp_rank: int,
moe_dp_rank: int,
nccl_port: int,
target_worker: TpModelWorker,
):
# Parse arguments
self.server_args = server_args
self.topk = server_args.speculative_eagle_topk
self.speculative_num_steps = server_args.speculative_num_steps
self.speculative_num_draft_tokens = server_args.speculative_num_draft_tokens
self.gpu_id = gpu_id
self.device = server_args.device
self.target_worker = target_worker
self.page_size = server_args.page_size
self.speculative_algorithm = SpeculativeAlgorithm.from_string(
server_args.speculative_algorithm
)
self.draft_extend_attn_backend_list = []
# Override the context length of the draft model to be the same as the target model.
server_args.context_length = target_worker.model_runner.model_config.context_len
# Do not capture cuda graph in `super().__init__()`
# It will be captured later.
backup_disable_cuda_graph = server_args.disable_cuda_graph
server_args.disable_cuda_graph = True
# Share the allocator with a target worker.
# Draft and target worker own their own KV cache pools.
self.req_to_token_pool, self.token_to_kv_pool_allocator = (
target_worker.get_memory_pool()
)
# Load hot token ids
if self.speculative_algorithm.is_eagle3():
if server_args.speculative_token_map is not None:
logger.warning(
"Speculative token map specified, but EAGLE3 models already have this. Ignoring the specified token map."
)
self.hot_token_id = None
elif server_args.speculative_token_map is not None:
self.hot_token_id = load_token_map(server_args.speculative_token_map)
server_args.json_model_override_args = (
f'{{"hot_vocab_size": {len(self.hot_token_id)}}}'
)
else:
self.hot_token_id = None
# Init draft worker
if server_args.enable_dp_attention and self.speculative_algorithm.is_eagle3():
ctx = draft_tp_context(get_attention_tp_group())
else:
ctx = empty_context()
with ctx, speculative_moe_backend_context():
super().__init__(
server_args=server_args,
gpu_id=gpu_id,
tp_rank=tp_rank,
pp_rank=0, # FIXME
dp_rank=dp_rank,
moe_ep_rank=moe_ep_rank,
attn_cp_rank=attn_cp_rank,
moe_dp_rank=moe_dp_rank,
nccl_port=nccl_port,
is_draft_worker=True,
req_to_token_pool=self.req_to_token_pool,
token_to_kv_pool_allocator=self.token_to_kv_pool_allocator,
memory_pool_config=target_worker.model_runner.memory_pool_config,
is_multi_layer_eagle=True,
)
embed, head = self.target_worker.model_runner.model.get_embed_and_head()
if self.speculative_algorithm.is_eagle3():
# most cases EAGLE3 models don't share lm_head
# but some models (e.g. nvidia/gpt-oss-120b-Eagle3) shares
if (
hasattr(self.draft_model_runner.model, "load_lm_head_from_target")
and self.draft_model_runner.model.load_lm_head_from_target
):
self.draft_model_runner.model.set_embed_and_head(embed, head)
else:
self.draft_model_runner.model.set_embed(embed)
# grab hot token ids
if self.draft_model_runner.model.hot_token_id is not None:
self.hot_token_id = self.draft_model_runner.model.hot_token_id.to(
embed.device
)
else:
if self.hot_token_id is not None:
head = head.clone()
self.hot_token_id = self.hot_token_id.to(head.device)
head.data = head.data[self.hot_token_id]
# Share the embedding and lm_head
for i in range(self.speculative_num_steps):
self.mtp_model_runner(i).model.set_embed_and_head(embed, head)
# Init attention backend and cuda graphs
for i in range(self.speculative_num_steps):
self.mtp_model_runner(i).server_args.disable_cuda_graph = (
backup_disable_cuda_graph
)
self.draft_tp_context = (
draft_tp_context if server_args.enable_dp_attention else empty_context
)
with self.draft_tp_context(
self.mtp_model_runner(0).tp_group
), speculative_moe_backend_context():
self.init_attention_backend()
self.init_cuda_graphs()
# Some dummy tensors
self.num_new_pages_per_topk = torch.empty(
(), dtype=torch.int64, device=self.device
)
self.extend_lens = torch.empty((), dtype=torch.int64, device=self.device)
def init_attention_backend(self):
# Create multi-step attn backends and cuda graph runners
for step in range(self.speculative_num_steps):
draft_backend_factory = DraftBackendFactory(
self.server_args,
self.mtp_model_runner(step),
self.topk,
self.speculative_num_steps,
)
# Initialize draft extend attention backend (respects speculative_attention_mode setting)
self.draft_extend_attn_backend_list.append(
draft_backend_factory.create_draft_extend_backend()
)
def init_cuda_graphs(self):
"""Capture cuda graphs."""
self.cuda_graph_runner_for_draft_extend_list = []
if self.server_args.disable_cuda_graph:
return
# Capture extend
for step in range(self.speculative_num_steps):
if self.draft_extend_attn_backend_list[step] and not _is_npu:
tic = time.perf_counter()
before_mem = get_available_gpu_memory(self.device, self.gpu_id)
logger.info(
f"Capture draft extend cuda graph begin. This can take up to several minutes. avail mem={before_mem:.2f} GB"
)
self.cuda_graph_runner_for_draft_extend_list.append(
MultiLayerEagleDraftExtendCudaGraphRunner(self, step)
)
after_mem = get_available_gpu_memory(self.device, self.gpu_id)
logger.info(
f"Capture draft extend cuda graph end. Time elapsed: {time.perf_counter() - tic:.2f} s. mem usage={(before_mem - after_mem):.2f} GB. avail mem={after_mem:.2f} GB."
)
def mtp_model_runner(self, layer_id: int) -> ModelRunner:
return self.model_runner_list[layer_id]
def forward_batch_generation(self, batch: ScheduleBatch) -> GenerationBatchResult:
"""Run speculative decoding forward.
NOTE: Many states of batch is modified as you go through. It is not guaranteed that
the final output batch have the same state as the input.
Args:
batch: The batch to run forward. The state of the batch is modified as it runs.
Returns:
A tuple of the final logit output of the target model, next tokens accepted,
the batch id (used for overlap schedule), and number of accepted tokens.
"""
if batch.forward_mode.is_extend() or batch.is_extend_in_batch:
logits_output, next_token_ids, seq_lens_cpu = self.forward_target_extend(
batch
)
with self.draft_tp_context(
self.mtp_model_runner(0).tp_group
), speculative_moe_backend_context():
self.forward_draft_extend(
batch, logits_output.hidden_states, next_token_ids, seq_lens_cpu
)
return GenerationBatchResult(
logits_output=logits_output,
next_token_ids=next_token_ids,
num_accepted_tokens=0,
can_run_cuda_graph=False,
)
else:
with self.draft_tp_context(
self.mtp_model_runner(0).tp_group
), speculative_moe_backend_context():
spec_info = self.draft(batch)
logits_output, verify_output, model_worker_batch, can_run_cuda_graph = (
self.verify(batch, spec_info)
)
with self.draft_tp_context(
self.mtp_model_runner(0).tp_group
), speculative_moe_backend_context():
# NOTE: We should use `check_forward_draft_extend_after_decode`
# when DP attention is enabled, but it is slow. Skip it for now.
if (
self.server_args.enable_dp_attention
or batch.spec_info.verified_id.shape[0] > 0
):
# decode is not finished
self.forward_draft_extend_after_decode(batch)
return GenerationBatchResult(
logits_output=logits_output,
next_token_ids=verify_output.verified_id,
num_accepted_tokens=sum(verify_output.accept_length_per_req_cpu),
can_run_cuda_graph=can_run_cuda_graph,
)
def check_forward_draft_extend_after_decode(self, batch: ScheduleBatch):
local_need_forward = batch.spec_info.verified_id.shape[0] > 0
if not self.server_args.enable_dp_attention:
return local_need_forward
global_need_forward = torch.tensor(
[
(local_need_forward),
],
dtype=torch.int64,
)
torch.distributed.all_reduce(
global_need_forward, group=get_tp_group().cpu_group
)
global_need_forward_cnt = global_need_forward[0].item()
need_forward = global_need_forward_cnt > 0
return need_forward
def forward_target_extend(
self, batch: ScheduleBatch
) -> Tuple[LogitsProcessorOutput, torch.Tensor, int, Optional[torch.Tensor]]:
"""Run the target extend.
Args:
batch: The batch to run. States could be modified.
Returns:
logits_output: The output of logits. It will contain the full hidden states.
next_token_ids: Next token ids generated.
"""
# Forward with the target model and get hidden states.
# We need the full hidden states to prefill the KV cache of the draft model.
model_worker_batch = batch.get_model_worker_batch()
model_worker_batch.capture_hidden_mode = CaptureHiddenMode.FULL
model_worker_batch.return_hidden_states_before_norm = True
batch_result = self.target_worker.forward_batch_generation(model_worker_batch)
logits_output, next_token_ids = (
batch_result.logits_output,
batch_result.next_token_ids,
)
return (
logits_output,
next_token_ids,
model_worker_batch.seq_lens_cpu,
)
def _draft_preprocess_decode(self, batch: ScheduleBatch):
from sglang.srt.speculative.eagle_worker import EAGLEWorker
# FIXME: migrate multi-layer eagle worker to eagle worker
return EAGLEWorker._draft_preprocess_decode(self, batch)
def _draft_preprocess_idle(self, batch: ScheduleBatch):
from sglang.srt.speculative.eagle_worker import EAGLEWorker
# FIXME: migrate multi-layer eagle worker to eagle worker
return EAGLEWorker._draft_preprocess_idle(self, batch)
def draft(self, batch: ScheduleBatch):
# Parse args
if batch.forward_mode.is_idle():
self._draft_preprocess_idle(batch)
else:
self._draft_preprocess_decode(batch)
spec_info = batch.spec_info
assert isinstance(spec_info, EagleDraftInput)
spec_info.capture_hidden_mode = CaptureHiddenMode.LAST
spec_info.num_tokens_per_req = self.topk
spec_info.num_tokens_for_logprob_per_req = self.topk
batch.return_hidden_states = False
# Get forward batch
model_worker_batch = batch.get_model_worker_batch()
assert model_worker_batch.capture_hidden_mode == CaptureHiddenMode.LAST
forward_batch = ForwardBatch.init_new(
model_worker_batch, self.mtp_model_runner(0)
)
forward_batch.can_run_dp_cuda_graph = False
forward_batch.return_hidden_states_before_norm = True
# Parse args
assert isinstance(spec_info, EagleDraftInput)
topk_p, topk_index, hidden_states = (
spec_info.topk_p,
spec_info.topk_index,
spec_info.hidden_states,
)
maybe_detect_nan(topk_p, "draft: NaN in initial topk_p from spec_info")
# Return values
score_list: List[torch.Tensor] = []
token_list: List[torch.Tensor] = []
parents_list: List[torch.Tensor] = []
# Forward multiple steps
scores = None
input_ids, hidden_states, scores, tree_info = select_top_k_tokens(
0, topk_p, topk_index, hidden_states, scores, self.topk
)
if self.speculative_num_steps == 1:
score_list.append(tree_info[0])
token_list.append(tree_info[1])
parents_list.append(tree_info[2])
else:
for i in range(self.speculative_num_steps):
score_list.append(tree_info[0][:, :, i].unsqueeze(-1))
token_index = tree_info[1][:, i].unsqueeze(-1)
token_list.append(token_index)
if i == 0:
parents_list.append(tree_info[2])
else:
parents_list.append(
torch.full(
(tree_info[2].size(0), 1),
i,
dtype=torch.long,
device=self.device,
)
)
parent_list, top_scores_index, draft_tokens = organize_draft_results(
score_list, token_list, parents_list, self.speculative_num_draft_tokens
)
if batch.forward_mode.is_idle():
return EagleVerifyInput.create_idle_input(
self.topk,
self.speculative_num_steps,
self.speculative_num_draft_tokens,
)
(
tree_mask,
position,
retrive_index,
retrive_next_token,
retrive_next_sibling,
draft_tokens,
) = build_tree_kernel_efficient(
spec_info.verified_id,
parent_list,
top_scores_index,
draft_tokens,
batch.seq_lens,
batch.seq_lens_sum,
self.topk,
self.speculative_num_steps,
self.speculative_num_draft_tokens,
)
return EagleVerifyInput(
draft_token=draft_tokens,
custom_mask=tree_mask,
positions=position,
retrive_index=retrive_index,
retrive_next_token=retrive_next_token,
retrive_next_sibling=retrive_next_sibling,
retrive_cum_len=None,
spec_steps=self.speculative_num_steps,
topk=self.topk,
draft_token_num=self.server_args.speculative_num_draft_tokens,
capture_hidden_mode=CaptureHiddenMode.FULL,
seq_lens_sum=forward_batch.seq_lens_sum,
seq_lens_cpu=forward_batch.seq_lens_cpu,
)
def clear_cache_pool(self):
# allocator and kv cache pool are shared with target worker
pass
def verify(self, batch: ScheduleBatch, spec_info: EagleVerifyInput):
spec_info.prepare_for_verify(batch, self.page_size)
batch.return_hidden_states = False
batch.forward_mode = (
ForwardMode.TARGET_VERIFY
if not batch.forward_mode.is_idle()
else ForwardMode.IDLE
)
batch.spec_info = spec_info
model_worker_batch = batch.get_model_worker_batch(
seq_lens_cpu_cache=spec_info.seq_lens_cpu
)
assert model_worker_batch.capture_hidden_mode == spec_info.capture_hidden_mode
model_worker_batch.return_hidden_states_before_norm = True
if batch.has_grammar:
retrieve_next_token_cpu = spec_info.retrive_next_token.cpu()
retrieve_next_sibling_cpu = spec_info.retrive_next_sibling.cpu()
draft_tokens_cpu = spec_info.draft_token.view(
spec_info.retrive_next_token.shape
).cpu()
# Forward
batch_result = self.target_worker.forward_batch_generation(
model_worker_batch, is_verify=True
)
logits_output, can_run_cuda_graph = (
batch_result.logits_output,
batch_result.can_run_cuda_graph,
)
vocab_mask = None
if batch.has_grammar:
# Generate the logit mask for structured output.
# Overlap the CPU operations for bitmask generation with the forward pass.
vocab_mask = generate_token_bitmask(
batch.reqs,
spec_info,
retrieve_next_token_cpu,
retrieve_next_sibling_cpu,
draft_tokens_cpu,
batch.sampling_info.vocab_size,
)
if vocab_mask is not None:
assert spec_info.grammar is not None
vocab_mask = vocab_mask.to(spec_info.retrive_next_token.device)
# NOTE (sk): otherwise, this vocab mask will be the one from the previous extend stage
# and will be applied to produce wrong results
batch.sampling_info.vocab_mask = None
maybe_detect_nan(logits_output.next_token_logits, "verify: target model logits")
spec_info.hidden_states = logits_output.hidden_states
res: EagleVerifyOutput = spec_info.verify(
batch,
logits_output,
self.token_to_kv_pool_allocator,
self.page_size,
vocab_mask,
)
# Post process based on verified outputs.
# Pick indices that we care (accepted)
logits_output.next_token_logits = logits_output.next_token_logits[
res.accepted_indices
]
logits_output.hidden_states = logits_output.hidden_states[res.accepted_indices]
if self.target_worker.model_runner.hybrid_gdn_config is not None:
accepted_length = (
torch.tensor(
res.accept_length_per_req_cpu,
device=logits_output.hidden_states.device,
dtype=torch.int64,
)
+ 1
)
# If topk > 1, we need to use retrieve_next_token and retrieve_next_sibling to handle the eagle tree custom attention mask
# res.accepted_indices.shape[0] > 0 skips DP attn idle batch
if spec_info.topk > 1 and res.accepted_indices.shape[0] > 0:
# accepted_indices=[0,2,3,4,5,7,9,10,11], accepted_length=[4, 3, 2], cumulative_accepted_lengths=[4, 7, 9]
# first_token_indices_per_req=prepend(0, accepted_indices[cumulative_accepted_lengths[:-1]]) = [0, 5, 10]
# last_token_indices_per_req=accepted_indices[cumulative_accepted_lengths - 1] = [4, 9, 11] (last token ID of each req)
# max_relative_indices_per_req = [4,4,1]; those are the per-req spec-decoding step offsets that contain the correct mamba caches
cumulative_accepted_lengths = torch.cumsum(accepted_length, dim=0)
req_start_positions = torch.cat(
[
torch.zeros(
1,
dtype=cumulative_accepted_lengths.dtype,
device=cumulative_accepted_lengths.device,
),
cumulative_accepted_lengths[:-1],
]
)
first_token_indices_per_req = res.accepted_indices[req_start_positions]
last_token_indices_per_req = res.accepted_indices[
cumulative_accepted_lengths - 1
]
max_relative_indices_per_req = (
last_token_indices_per_req - first_token_indices_per_req
)
else:
max_relative_indices_per_req = accepted_length - 1
self.target_worker.model_runner.attn_backend.update_mamba_state_after_mtp_verify(
max_relative_indices_per_req, self.target_worker.model_runner.model
)
if batch.return_logprob:
add_output_logprobs_for_spec_v1(batch, res, logits_output)
# Prepare the batch for the next draft forwards.
batch.forward_mode = (
ForwardMode.DECODE if not batch.forward_mode.is_idle() else ForwardMode.IDLE
)
batch.spec_info = res.draft_input
return logits_output, res, model_worker_batch, can_run_cuda_graph
def forward_draft_extend(
self,
batch: ScheduleBatch,
hidden_states: torch.Tensor,
next_token_ids: torch.Tensor,
seq_lens_cpu: Optional[torch.Tensor],
):
"""Run draft model extend. This API modifies the states of the batch.
Args:
batch: The batch to run.
hidden_states: Hidden states from the target model forward
next_token_ids: Next token ids generated from the target forward.
"""
batch.spec_info = EagleDraftInput(
hidden_states=hidden_states,
verified_id=next_token_ids,
num_tokens_per_req=1,
num_tokens_for_logprob_per_req=1,
)
batch.return_hidden_states = False
batch.spec_info.prepare_for_extend(batch)
batch.spec_info.capture_hidden_mode = CaptureHiddenMode.LAST
model_worker_batch = batch.get_model_worker_batch(
seq_lens_cpu_cache=seq_lens_cpu
)
forward_batch = ForwardBatch.init_new(
model_worker_batch, self.mtp_model_runner(0)
)
forward_batch.return_logprob = False
forward_batch.return_hidden_states_before_norm = True
topk_p_list = []
topk_index_list = []
for step in range(self.speculative_num_steps):
logits_output = (
self.mtp_model_runner(step).forward(forward_batch).logits_output
)
maybe_detect_nan(
logits_output.next_token_logits,
f"draft_extend_for_prefill step {step}",
)
probs = torch.softmax(logits_output.next_token_logits, dim=-1)
topk_p, topk_index = fast_topk(probs, self.topk, dim=-1)
topk_p_list.append(topk_p)
topk_index_list.append(topk_index)
pt = 0
if forward_batch.extend_seq_lens is not None:
for i, extend_len in enumerate(forward_batch.extend_seq_lens):
input_ids = forward_batch.input_ids[pt : pt + extend_len]
forward_batch.input_ids[pt : pt + extend_len] = torch.cat(
(input_ids[1:], topk_index[i].reshape(1))
)
pt += extend_len
assert isinstance(forward_batch.spec_info, EagleDraftInput)
assert forward_batch.spec_info is batch.spec_info
forward_batch.spec_info.topk_p = torch.cat(topk_p_list, dim=1)
forward_batch.spec_info.topk_index = torch.cat(topk_index_list, dim=1)
def forward_draft_extend_after_decode(self, batch: ScheduleBatch):
assert isinstance(batch.spec_info, EagleDraftInput)
# Backup fields that will be modified in-place
seq_lens_backup = batch.seq_lens.clone()
seq_lens_cpu_backup = batch.seq_lens_cpu.clone()
req_pool_indices_backup = batch.req_pool_indices
accept_length_backup = batch.spec_info.accept_length
return_logprob_backup = batch.return_logprob
input_is_idle = batch.forward_mode.is_idle()
if not input_is_idle and batch.spec_info.verified_id.numel() == 0:
batch = batch.copy()
batch.prepare_for_idle()
hidden_size = (
self.model_config.hidden_size * 3
if self.speculative_algorithm.is_eagle3()
else self.model_config.hidden_size
)
batch.spec_info = EagleDraftInput.create_idle_input(
device=self.device,
hidden_size=hidden_size,
dtype=self.model_config.dtype,
topk=self.topk,
capture_hidden_mode=CaptureHiddenMode.LAST,
)
batch.spec_info.num_tokens_per_req = self.speculative_num_steps + 1
batch.spec_info.num_tokens_for_logprob_per_req = 1
batch.spec_info.prepare_extend_after_decode(
batch,
self.speculative_num_steps,
)
batch.forward_mode = (
ForwardMode.DRAFT_EXTEND
if not batch.forward_mode.is_idle()
else ForwardMode.IDLE
)
batch.return_hidden_states = False
model_worker_batch = batch.get_model_worker_batch()
assert model_worker_batch.capture_hidden_mode == CaptureHiddenMode.LAST
forward_batch = ForwardBatch.init_new(
model_worker_batch, self.mtp_model_runner(0)
)
forward_batch.return_hidden_states_before_norm = True
if forward_batch.seq_lens_cpu is not None:
forward_batch.seq_lens_sum = forward_batch.seq_lens_cpu.sum().item()
else:
forward_batch.seq_lens_sum = batch.seq_lens.sum().item()
topk_p_list = []
topk_index_list = []
# Run
for step in range(self.speculative_num_steps):
can_cuda_graph = len(
self.cuda_graph_runner_for_draft_extend_list
) and self.cuda_graph_runner_for_draft_extend_list[step].can_run(
forward_batch
)
if can_cuda_graph:
logits_output = self.cuda_graph_runner_for_draft_extend_list[
step
].replay(forward_batch)
else:
forward_batch.can_run_dp_cuda_graph = False
if not forward_batch.forward_mode.is_idle():
self.mtp_model_runner(step).attn_backend.init_forward_metadata(
forward_batch
)
logits_output = (
self.mtp_model_runner(step)
.forward(forward_batch, skip_attn_backend_init=True)
.logits_output
)
maybe_detect_nan(
logits_output.next_token_logits,
f"draft_extend_after_decode step {step} (cuda_graph={can_cuda_graph})",
)
probs = torch.softmax(logits_output.next_token_logits, dim=-1)
topk_p, topk_index = fast_topk(probs, self.topk, dim=-1)
topk_p_list.append(topk_p)
topk_index_list.append(topk_index)
pt = 0
if forward_batch.extend_seq_lens is not None:
for i, extend_len in enumerate(forward_batch.extend_seq_lens):
input_ids = forward_batch.input_ids[pt : pt + extend_len]
forward_batch.input_ids[pt : pt + extend_len] = torch.cat(
(input_ids[1:], topk_index[i].reshape(1))
)
pt += extend_len
forward_batch.spec_info.topk_p = torch.cat(topk_p_list, dim=1)
forward_batch.spec_info.topk_index = torch.cat(topk_index_list, dim=1)
# Restore backup.
# This is because `seq_lens` can be modified in `prepare_extend_after_decode`
batch.forward_mode = (
ForwardMode.DECODE if not input_is_idle else ForwardMode.IDLE
)
batch.seq_lens = seq_lens_backup
batch.seq_lens_cpu = seq_lens_cpu_backup
batch.req_pool_indices = req_pool_indices_backup
batch.spec_info.accept_length = accept_length_backup
batch.return_logprob = return_logprob_backup