kel-dx/llm-jp-4-8b-instruct-NVFP4-speculator.dflash

llm-jp-4-8b-instruct-NVFP4 DFlash Drafter

This repository contains a DFlash draft model for speculative decoding with kel-jp/llm-jp-4-8b-instruct-NVFP4.

This is not a standalone text-generation model. Use it as the draft/speculator model while serving the NVFP4 model as the verifier in stock vLLM.

Intended Use

• Verifier model: kel-jp/llm-jp-4-8b-instruct-NVFP4
• Drafting method: dflash
• Draft architecture: block size 4, 1 transformer layer, 28k draft vocabulary
• Proposal setting used in the released config: greedy, speculative_tokens=3
• Runtime target: stock vLLM with DFlash support

vLLM Example

vllm serve kel-jp/llm-jp-4-8b-instruct-NVFP4 \
  --trust-remote-code \
  --reasoning-parser llmjp4 \
  --speculative-config '{"method":"dflash","model":"kel-jp/llm-jp-4-8b-instruct-NVFP4-speculator.dflash","num_speculative_tokens":3}'

If you use an environment wrapper, set the same JSON as SPECULATIVE_CONFIG. The verifier model still needs the serving requirements documented on the NVFP4 model page, including the LLM-jp remote code/plugin setup.

Benchmark (DGX Spark / GB10, SM121)

Representative Japanese streaming decode benchmark on ELYZA-100 prompts, measured on NVIDIA DGX Spark / GB10 (SM121) with vLLM 0.24.0, stock vLLM DFlash, temperature 0, serial streaming requests, and exactly 128 generated tokens per request. Decode speed excludes time-to-first-token.

Setup	Mean decode tok/s	Speedup vs BF16	Notes
BF16 base model	14.42	1.00x	llm-jp/llm-jp-4-8b-instruct, no speculative decoding
NVFP4 verifier	29.73	2.06x	kel-jp/llm-jp-4-8b-instruct-NVFP4, no speculative decoding
NVFP4 + this DFlash drafter	49.04	3.40x	stock vLLM DFlash, num_speculative_tokens=3

The DFlash row is 1.65x faster than the NVFP4 verifier baseline by ratio of standalone means. In the paired per-prompt run against the same NVFP4 baseline, the DFlash mean was 48.76 tok/s and the ratio of mean decode throughput was 1.64x.

Paired speedup summary:

• Ratio of mean decode throughput: 1.64x
• Mean paired request speedup: 1.64x
• Median paired request speedup: 1.63x
• p05/p95 paired speedup: 1.37x / 1.97x
• Requests at least 1.5x faster: 70 / 100
• Requests at least 2.0x faster: 5 / 100
• Requests slower than baseline: 0 / 100

The raw benchmark artifacts are included under benchmark/:

• bf16-elyza100-streaming.json
• bf16-elyza100-streaming.csv
• baseline-elyza100-streaming.json
• baseline-elyza100-streaming.csv
• dflash20k-b4-l1-v28k-elyza100-streaming.json
• dflash20k-b4-l1-v28k-elyza100-streaming.csv
• elyza100-bf16-nvfp4-dflash-speedup-summary.json
• elyza100-bf16-nvfp4-dflash-speedup.png
• elyza100-baseline-vs-dflash-summary.json
• elyza100-baseline-vs-dflash-speedup.png
• dflash20k-b4-l1-elyza100-tps-histogram.png

Validation Metrics

The released checkpoint's held-out validation metrics:

{
  "loss_epoch": 2.047496609403255,
  "full_acc_epoch": 0.4021220020978507,
  "position_1_acc_epoch": 0.5539027137301571,
  "position_2_acc_epoch": 0.38056573750461736,
  "position_3_acc_epoch": 0.27111557473966125
}

Files

• model.safetensors: released drafter weights
• config.json: DFlash/speculators configuration consumed by vLLM
• config.py: custom config class required by the drafter
• val_metrics.json: validation metrics from the selected checkpoint
• benchmark/: benchmark summaries, per-request CSV/JSON, and plots

Limitations

• This artifact is useful only with a compatible verifier model and DFlash-capable vLLM runtime.
• The published benchmark is throughput-oriented and uses Japanese ELYZA-100 prompts. It is not a general quality evaluation of the verifier model.
• Speedup depends on prompt mix, max token settings, batching, hardware, and vLLM version.

License

Apache-2.0, following the verifier model release.