RedHatAI/Qwen3.8-27B-speculator.dspark
Model Overview
- Model Architecture:
DSparkDraftModel
- Target Model Architecture:
Qwen3_5ForConditionalGeneration
- Input: Text
- Output: Text
- Model Optimizations:
- Speculative Decoding Algorithm: DSpark
- Draft Model: 5-layer Qwen3-style backbone
- Maximum Draft Length: 8 tokens
- Auxiliary Target Layers: 4, 12, 20, 28, 36, 44, 52, and 60
- Markov Head: Vanilla, rank 256
- Confidence Head: Enabled with Markov features
- Configured Maximum Context Length: 262,144 tokens
- Release Date: 2026-09-21
- Version: 1.0
- Model Developers: Red Hat AI
This is a DSpark speculator model for Qwen3.8-27B. It was trained using the Speculators library (version 0.8.0.dev221).
DSpark extends DFlash with a Markov head for modeling intra-block token dependencies and a confidence head for predicting per-position acceptance. The 5-layer draft model consumes auxiliary hidden states from layers 4, 12, 20, 28, 36, 44, 52, and 60 of the target model and proposes up to 8 tokens per decoding step.
Training Details
This checkpoint was warm-started from an earlier Qwen3.8-27B DSpark checkpoint and trained on a Qwen3.8-27B-regenerated version of Open PerfectBlend. Data preparation produced 1,739,710 8,192-token training examples with a 99/1 train-validation split. Hidden-state extraction used four independent vLLM data-parallel replicas, while four FSDP ranks trained the draft model.
The released checkpoint is from global step 107,520, or approximately 75% of the planned one-epoch run. It used the full verifier vocabulary, sample_from_anchor=true, and up to 1,024 anchors per sequence.
Key training configuration
Hidden-state extraction used vLLM 0.29.0 with data-parallel size 4, tensor-parallel size 1, and target layer IDs 4 12 20 28 36 44 52 60. Training used Speculators commit 876e2b6.
Model Specifications
Deployment
Acceptance Rates
Evaluation used vLLM 0.29.0, a dense Qwen/Qwen3.8-27B verifier.
Per-position acceptance rates:
Long-Context Acceptance
Evaluation of RedHatAI/Qwen3.8-27B-speculator.dspark using 8 speculative tokens on MRCR 8-Needle.
- Maximum successful prompt length: 1,114,783 tokens
Performance Eval Against MTP
Across HumanEval, math reasoning, and RAG, DSpark consistently delivers higher throughput and better interactivity than MTP with the same eight speculative tokens. The advantage is strongest at low-to-medium concurrency—particularly for math reasoning—and remains positive at concurrency 128, though it narrows for RAG. Both methods scale smoothly, while DSpark sustains lower per-token latency as load increases.