f8d03d21f1
### What this PR does / why we need it?
`vllm_ascend` already supports several speculative decoding strategies
such as MTP, EAGLE, N-gram, and suffix decoding. However, Medusa is not
yet supported. Medusa is an efficient speculative decoding framework
that leverages a lightweight draft model to propose multiple tokens in a
single step, which can significantly improve decoding throughput and
reduce latency.
To enable Medusa-based speculative decoding on Ascend hardware and
provide more decoding options for users, this PR adds Medusa support
into the `vllm_ascend` speculative decoding pipeline.
### Does this PR introduce _any_ user-facing change?
This PR introduces Medusa speculative decoding as an additional
speculative decoding method:
✔ Adds `MedusaProposer` and integrates it into the speculative decoding
registry
✔ Extends `SpecDcodeType` with a `MEDUSA` enum entry
✔ Updates `NPUModelRunner` to recognize and invoke Medusa during
decoding
✔ Adds Medusa-specific handling in the draft token generation logic
✔ Ensures backward compatibility — Medusa is only used when explicitly
enabled
Key code changes include:
* New file: `vllm_ascend/spec_decode/medusa_proposer.py`
* Register Medusa in `get_spec_decode_method`
* Extend proposer type hints to include `MedusaProposer`
* Add a Medusa-specific branch in `generate_draft_token_ids`
* Pass `sample_hidden_states` required by Medusa
### How was this patch tested?
Medusa is implemented as a new proposer class (`MedusaProposer`)
following the existing speculative decoding interface. The integration
works as follows:
1. Users enable Medusa via the speculative decoding configuration.
2. `get_spec_decode_method()` returns a `MedusaProposer` instance when
`method="medusa"`.
3. During decoding, `NPUModelRunner` detects that the active drafter is
a `MedusaProposer`.
4. Instead of the generic speculative decoding path, the Medusa-specific
`generate_token_ids()` method is invoked, which consumes:
* `valid_sampled_token_ids`
* `sampling_metadata`
* `spec_decode_metadata`
* `sample_hidden_states`
5. The proposed tokens are validated by the target model as usual.
When Medusa is not enabled, the decoding pipeline behaves exactly as
before, ensuring full backward compatibility.
- vLLM version: v0.13.0
- vLLM main:
2f4e6548ef
Signed-off-by: simplzyu <191163281@qq.com>
Signed-off-by: simplzyu <zhenyuguo@cmbchina.com>
40 lines
1.7 KiB
Python
40 lines
1.7 KiB
Python
#
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# Copyright (c) 2025 Huawei Technologies Co., Ltd. All Rights Reserved.
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# Copyright 2023 The vLLM team.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# This file is a part of the vllm-ascend project.
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# Adapted from vllm-project/vllm/vllm/worker/gpu_model_runner.py
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#
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from vllm_ascend.spec_decode.eagle_proposer import EagleProposer
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from vllm_ascend.spec_decode.medusa_proposer import MedusaProposer
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from vllm_ascend.spec_decode.mtp_proposer import MtpProposer
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from vllm_ascend.spec_decode.ngram_proposer import NgramProposer
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from vllm_ascend.spec_decode.suffix_proposer import SuffixDecodingProposer
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def get_spec_decode_method(method, vllm_config, device, runner):
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if method == "ngram":
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return NgramProposer(vllm_config, device, runner)
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elif method in ("eagle", "eagle3"):
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return EagleProposer(vllm_config, device, runner)
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elif method == "mtp":
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return MtpProposer(vllm_config, device, runner)
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elif method == 'suffix':
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return SuffixDecodingProposer(vllm_config, device, runner)
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elif method == "medusa":
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return MedusaProposer(vllm_config, device, runner)
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else:
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raise ValueError("Unknown speculative decoding method: "
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f"{method}")
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