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enginex-hygon-vllm/vllm/zero_overhead/spec_decode/batch_expansion.py

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2026-01-09 15:09:53 +08:00
from array import array
import numpy as np
from itertools import chain, count
from typing import Iterator, List, Optional, Tuple
import torch
from vllm import SamplingParams
from vllm.model_executor.layers.sampler import SamplerOutput
from vllm.sequence import (VLLM_INVALID_TOKEN_ID, VLLM_TOKEN_ID_ARRAY_TYPE,
ExecuteModelRequest, SequenceData,
SequenceGroupMetadata, get_all_seq_ids)
from vllm.spec_decode.batch_expansion import BatchExpansionTop1Scorer
from vllm.spec_decode.interfaces import (SpeculativeProposals,
SpeculativeScorer, SpeculativeScores)
from vllm.spec_decode.util import nvtx_range, split_batch_by_proposal_len
from vllm.utils import async_tensor_h2d
from vllm.zero_overhead.utils import get_proposal_lens_list, record_proposal_token_ids
SeqId = int
TargetSeqId = int
TokenId = int
DEFAULT_SIMPLE_SAMPLING_PARAMS = SamplingParams()
class ZeroOverheadBatchExpansionTop1Scorer(BatchExpansionTop1Scorer):
@nvtx_range("BatchExpansionTop1Scorer.score_proposals")
def score_proposals(
self,
execute_model_req: ExecuteModelRequest,
proposals: SpeculativeProposals,
) -> SpeculativeScores:
"""Score the proposed tokens via the scorer model.
This converts each input sequence to a set of k+1 target sequences. The
target sequences have the unique continuations to be scored and a
unique sequence ID that is different from all input sequence ids.
If a speculative sequence length would exceed the max model length, then
no speculation is produced for that sequence.
Args:
execute_model_req: The execution request.
proposals: The speculative proposals to score.
Returns:
SpeculativeScores: The scores of each speculative token, along with
which sequences were ignored during scoring.
"""
proposal_lens_list = get_proposal_lens_list()
record_proposal_token_ids(proposals.proposal_token_ids)
proposal_token_ids_list = np.zeros(proposals.proposal_token_ids.shape, dtype=int).tolist() # place holder tokens
# Filter the list to ignore invalid proposals.
proposal_token_ids_list_without_skips = [
proposals for proposals in proposal_token_ids_list
if VLLM_INVALID_TOKEN_ID not in proposals
]
(spec_indices, non_spec_indices, target_seq_group_metadata_list,
num_scoring_tokens) = self._expand_batch(
seq_group_metadata_list=execute_model_req.seq_group_metadata_list,
proposal_token_ids_list=proposal_token_ids_list_without_skips,
proposal_lens_list=proposal_lens_list,
)
target_sampler_output = self._scorer_worker.execute_model(
execute_model_req=execute_model_req.clone(
seq_group_metadata_list=target_seq_group_metadata_list))
assert len(target_sampler_output) == 1, "expected single-step output"
target_sampler_output = target_sampler_output[0]
if not non_spec_indices:
# All sequence groups in batch have spec decoding enabled
return self._contract_batch_all_spec(
target_sampler_output=target_sampler_output,
proposals=proposals,
)
else:
# Batch has a mix of spec decode enabled and disabled seq groups
return self._contract_batch(
execute_model_req.seq_group_metadata_list,
target_sampler_output=target_sampler_output,
proposals=proposals,
num_scoring_tokens=num_scoring_tokens,
non_spec_indices=non_spec_indices,
spec_indices=spec_indices,
k=execute_model_req.num_lookahead_slots,
)
def _contract_non_speculative(
self, scores: SpeculativeScores,
seq_group_metadata_list: List[SequenceGroupMetadata],
non_spec_indices: List[int], non_spec_outputs: SpeculativeScores,
has_prompt_log: bool) -> SpeculativeScores:
"""
Augment input `scores` with non-speculative requests outputs.
This includes decode requests with speculation turned off, as well
as prefill requests when `enable_chunked_prefill` is set.
For the latter, prefills are further separated into terminal and
non-terminal chunks (from which no token is sampled).
"""
if not non_spec_indices:
return scores
if has_prompt_log:
# When prompt_logprobs is enabled, prefills yield output token
# (and respective prob) in the last entry (prompt|out):
# [.|.|.|prefill0_out|.|prefill1_out|decode0_out|..].
# With chunked prefill, non-terminal chunks have -1 on each
# position: they're still picked, but they're discarded later.
seq_meta = seq_group_metadata_list
nospec_sizes = torch.tensor([
seq_meta[i].token_chunk_size if seq_meta[i].is_prompt else 1
for i in non_spec_indices
])
nospec_sampled_token_idxs = torch.cumsum(nospec_sizes, 0).add_(-1)
else:
# In this case only sampled tokens are returned, select all.
nospec_sampled_token_idxs = list(
range(len(non_spec_outputs.token_ids)))
nospec_sampled_token_idxs = async_tensor_h2d(nospec_sampled_token_idxs, torch.int32,
self._device,
True)
non_spec_indices = async_tensor_h2d(non_spec_indices, torch.int32,
self._device,
True)
scores.token_ids[non_spec_indices, :1] = \
non_spec_outputs.token_ids[nospec_sampled_token_idxs].unsqueeze(1)
scores.probs[non_spec_indices, :1, :] = \
non_spec_outputs.probs[nospec_sampled_token_idxs].unsqueeze(1)
scores.logprobs[non_spec_indices, :1, :] = \
non_spec_outputs.logprobs[nospec_sampled_token_idxs].unsqueeze(1)
if scores.hidden_states is not None:
assert non_spec_outputs.hidden_states is not None
scores.hidden_states[non_spec_indices, :1, :] = \
non_spec_outputs.hidden_states[nospec_sampled_token_idxs].unsqueeze(1)
return scores