Files
xc-llm-ascend/vllm_ascend/spec_decode/ngram_proposer.py
Jade Zheng 51c8f60eb0 [Bugfix] Resolve MTP > 1 issue when lm head tp > 1 (#4254)
### What this PR does / why we need it?

Previously, the dummy run executed compute_logits only once, regardless
of num_speculative_tokens. This caused execute_model to hang on
compute_logits when lm head tensor parallelism exceeded 1. The fix
ensures compute_logits executes correctly during dummy run, matching
num_speculative_tokens.

I set the `non_blocking` argument to False when moving
`exceeds_max_model_len` to the CPU. From what I understand, using
`non_blocking=True` and immediately accessing the tensor on the CPU can
cause accuracy problems. However, this issue doesn't happen when
transferring data to a device. ref:
https://discuss.pytorch.org/t/should-we-set-non-blocking-to-true/38234/18

- vLLM version: v0.11.0
- vLLM main:
2918c1b49c

---------

Signed-off-by: Jade Zheng <zheng.shoujian@outlook.com>
2025-12-01 10:22:36 +08:00

74 lines
2.6 KiB
Python

import numpy as np
import torch
from vllm.config import CUDAGraphMode
from vllm.v1.spec_decode.ngram_proposer import \
NgramProposer as VllmNgramProposer
from vllm_ascend.spec_decode.interface import Proposer, SpecDcodeType
class NgramProposer(VllmNgramProposer, Proposer):
def __init__(self, vllm_config, device, runner):
super().__init__(vllm_config)
self.name = SpecDcodeType.NGRAM
self.device = device
self.runner = runner
def load_model(self, *args, **kwargs):
# No model to load.
pass
@torch.inference_mode()
def dummy_run(self,
num_tokens,
with_prefill=None,
skip_attn=None,
num_reqs=None,
num_tokens_across_dp=None,
aclgraph_runtime_mode: CUDAGraphMode = CUDAGraphMode.NONE,
batch_descriptor=None,
dummy_compute_logits=lambda hidden_states: None):
pass
def generate_token_ids(self,
valid_sampled_token_ids: list[np.ndarray],
sampling_metadata=None,
scheduler_output=None,
spec_decode_metadata=None,
positions=None,
num_scheduled_tokens=None,
hidden_states=None,
attn_metadata=None,
aux_hidden_states=None) -> list[list[int]]:
valid_ngram_requests = []
for i, sampled_ids in enumerate(valid_sampled_token_ids):
num_sampled_ids = sampled_ids.shape[0]
if not num_sampled_ids:
continue
req_id = self.runner.input_batch.req_ids[i]
if req_id in self.runner.input_batch.spec_decode_unsupported_reqs:
continue
num_tokens = self.runner.input_batch.num_tokens_no_spec[i]
if num_tokens >= self.runner.input_batch.max_model_len:
# Skip requests that have already reached the max model length.
continue
start_idx = self.runner.input_batch.num_tokens_no_spec[i]
end_idx = start_idx + num_sampled_ids
self.runner.input_batch.token_ids_cpu[
i, start_idx:end_idx] = sampled_ids
valid_ngram_requests.append(i)
draft_token_ids = self.batch_propose(
len(valid_sampled_token_ids),
valid_ngram_requests,
self.runner.input_batch.num_tokens_no_spec,
self.runner.input_batch.token_ids_cpu,
)
return draft_token_ids