[Feature] Reproducing Qwen3.6 35B-A3B DFlash Training

[Sylvan820]

Checklist

• 1. If the issue you raised is not a feature but a question, please raise a discussion at https://github.com/sgl-project/SpecForge/discussions/new/choose Otherwise, it will be closed.
• 2. Please use English, otherwise it will be closed.

Motivation

SpecForge Training Configuration

Target Model: Qwen3.6-35B-A3

• 40 layers, Qwen3.5 MoE architecture
• Hidden size: 5120, 32 attention heads, 8 KV heads

Draft Model Config: Based on qwen3.5-35b-a3b-dflash.json with modifications:

• 8 decoder layers
• Block size: 16

Training Script:

python -m torch.distributed.run --standalone --nproc_per_node 8 \
    scripts/train_dflash.py \
    --train-data-path cache/dataset/opc_train_regen_first_turn.jsonl \
    --num-epochs 10 \
    --batch-size 8 \
    --learning-rate 6e-4 \
    --warmup-ratio 0.04 \
    --max-grad-norm 1.0 \
    --max-length 4096 \
    --chat-template qwen3.5 \
    --num-anchors 512 \
    --loss-decay-gamma 7.0 \
    --target-model-backend sglang \
    --block-size 16 \
    --embedding-key model.language_model.embed_tokens.weight \
    --trust-remote-code

Dataset: opc_train_regen_first_turn.jsonl (2,508,380 samples)

• Custom training data, first-turn only, regenerated

Training Progress: Currently at epoch 0, step ~140,000 (training ongoing) around 1 epoch.

---

Benchmark Results

Evaluation Setup:

• SGLang 0.5.6.post2, TP=4, fa3 attention backend
• Draft window size: 4096
• MTPBench: bsz=64, output_len=28000, datasets: code/math/mtbench
• GSM8K: 128 prompts, concurrency=16
• SWE: 64 samples, 16 workers
• Accept length includes bonus token (+1)

SpecForge Results (Current)

Training Step	Code	Math	MTBench	GSM8K
24,000	1.96	2.07	1.99	2.55
122,000	2.65	2.83	2.24	-
140,000	2.77	2.78	2.32	2.89

Official DFlash Pair (Reference)

Target	Draft	Code	Math	MTBench	GSM8K
Qwen3.6-35B-A3B	Official DFlash	4.45	5.24	3.23	6.84

Are these results normal? After ~140K steps (~1 epoch), SpecForge accept_length reaches only ~2.9 on GSM8K. This is significantly lower than the official DFlash pair (4.4-6.8). Should we expect further improvement with 2-3 more epochs?

Related resources

No response

[xiangqianzsh]

@Sylvan820 HI, which version of sglang do you use, the defualt 0.5.9 version does not have the dflash feature

[Sylvan820]

@Sylvan820 HI, which version of sglang do you use, the defualt 0.5.9 version does not have the dflash feature

I use the Qwen3.5 35B-A3B example.sh

[xiangqianzsh]

@Sylvan820 HI, which version of sglang do you use, the defualt 0.5.9 version does not have the dflash feature

I use the Qwen3.5 35B-A3B example.sh

Could you share the versions of SpecForge, torch, and sglang you're using?

[Sylvan820]

@Sylvan820 HI, which version of sglang do you use, the defualt 0.5.9 version does not have the dflash feature

I use the Qwen3.5 35B-A3B example.sh

Could you share the versions of SpecForge, torch, and sglang you're using?

We are using the latest versions in our current environment:

• SpecForge: latest main checkout, package version 0.2.0
• torch: 2.9.1+cu128
• sglang: 0.5.6.post2 for inference 0.5.9 for training

CUDA version is 12.8.

[xiangqianzsh]

@Sylvan820 HI, which version of sglang do you use, the defualt 0.5.9 version does not have the dflash feature

I use the Qwen3.5 35B-A3B example.sh

Could you share the versions of SpecForge, torch, and sglang you're using?

We are using the latest versions in our current environment:

• SpecForge: latest main checkout, package version 0.2.0
• torch: 2.9.1+cu128
• sglang: 0.5.6.post2 for inference 0.5.9 for training

CUDA version is 12.8.

sglang support dflash since 0.5.11(or 0.5.10), and how you evaluate accept_length of dflash ?

[Sylvan820]

@Sylvan820 HI, which version of sglang do you use, the defualt 0.5.9 version does not have the dflash feature

I use the Qwen3.5 35B-A3B example.sh

Could you share the versions of SpecForge, torch, and sglang you're using?

We are using the latest versions in our current environment:

• SpecForge: latest main checkout, package version 0.2.0
• torch: 2.9.1+cu128
• sglang: 0.5.6.post2 for inference 0.5.9 for training

CUDA version is 12.8.

sglang support dflash since 0.5.11(or 0.5.10), and how you evaluate accept_length of dflash ?

？？？

[xiangqianzsh]

@Sylvan820 HI, which version of sglang do you use, the defualt 0.5.9 version does not have the dflash feature

I use the Qwen3.5 35B-A3B example.sh

Could you share the versions of SpecForge, torch, and sglang you're using?

We are using the latest versions in our current environment:

• SpecForge: latest main checkout, package version 0.2.0
• torch: 2.9.1+cu128
• sglang: 0.5.6.post2 for inference 0.5.9 for training

CUDA version is 12.8.

sglang support dflash since 0.5.11(or 0.5.10), and how you evaluate accept_length of dflash ?

？？？
I also want to test the speed of dflash, but I find dflash was merged to sglang main branch since 2026-04-07 (ref: sgl-project/sglang#22077), newer than 0.5.9 and 0.5.6.post2, so I can not test it in SpecForge( same as #520)

[Sylvan820]

@Sylvan820 HI, which version of sglang do you use, the defualt 0.5.9 version does not have the dflash feature

I use the Qwen3.5 35B-A3B example.sh

Could you share the versions of SpecForge, torch, and sglang you're using?

We are using the latest versions in our current environment:

• SpecForge: latest main checkout, package version 0.2.0
• torch: 2.9.1+cu128
• sglang: 0.5.6.post2 for inference 0.5.9 for training

CUDA version is 12.8.

sglang support dflash since 0.5.11(or 0.5.10), and how you evaluate accept_length of dflash ?

？？？
I also want to test the speed of dflash, but I find dflash was merged to sglang main branch since 2026-04-07 (ref: sgl-project/sglang#22077), newer than 0.5.9 and 0.5.6.post2, so I can not test it in SpecForge( same as #520)

Oh, ok. I test it in DLFASH official sglang environment sglang 0.5.6. you can get it in dflash github.

[xiangqianzsh]

@Sylvan820 HI, which version of sglang do you use, the defualt 0.5.9 version does not have the dflash feature

I use the Qwen3.5 35B-A3B example.sh

Could you share the versions of SpecForge, torch, and sglang you're using?

We are using the latest versions in our current environment:

• SpecForge: latest main checkout, package version 0.2.0
• torch: 2.9.1+cu128
• sglang: 0.5.6.post2 for inference 0.5.9 for training

CUDA version is 12.8.

sglang support dflash since 0.5.11(or 0.5.10), and how you evaluate accept_length of dflash ?

？？？
I also want to test the speed of dflash, but I find dflash was merged to sglang main branch since 2026-04-07 (ref: sgl-project/sglang#22077), newer than 0.5.9 and 0.5.6.post2, so I can not test it in SpecForge( same as #520)

Oh, ok. I test it in DLFASH official sglang environment sglang 0.5.6. you can get it in dflash github.

Ok, thanks