Inkling-Small DSpark speculator
Overview
A DSpark speculator for the Inkling-Small NVFP4 target, enabling faster inference through speculative decoding. DSpark extends the DFlash parallel-draft backbone with a Markov logit-bias head and a per-position confidence head. This checkpoint was trained with SpecForge using hidden states from a live SGLang target engine.
Model Specifications
- Base model:
thinkingmachines/Inkling-Small-NVFP4; the exact matching target checkpoint and tokenizer are required. - Format: Safetensors (single-file BF16, 1.39B trainable parameters; draft weights only).
- Draft: 6 layers (Qwen3-style GQA), hidden 4096, 32 heads / 8 KV heads, head_dim 128, FFN 12288, rope_theta 8000000,
block_size=7. - RoPE: YaRN, factor 128,
original_max_position_embeddings=8192,max_position_embeddings=1048576(matches the target addressable range); config carries bothrope_scalingandrope_parametersschemas. - Vocabulary: 200,058 tokenizer entries and 201,024 padded weight rows;
mask_token_id=200064. - DSpark heads: Markov rank 256 (vanilla) and confidence head (with-Markov).
- Aux hidden-state layers:
[1, 6, 12, 17, 23, 28, 34, 39]. - Trained context: 8,192 native; long-context adaptation with sequences up to 65,536.
- Target weights: target embedding and unembedding weights are not included in this checkpoint.
Evaluation Results
Acceptance length over the full DeepSpec workload datasets. DSPARK block size 7, thinking effort 0.99, temperature 0 and temperature 1.0 / top-p 0.95:
| Dataset | n | acc_len @ T=0 | acc_len @ T=1 |
|---|---|---|---|
| GSM8K | 1,319 | 5.4254 | 5.2700 |
| MATH500 | 500 | 4.8009 | 4.6787 |
| MBPP | 257 | 4.1515 | 4.0105 |
| HumanEval | 164 | 3.9911 | 3.9084 |
| MT-Bench | 80 | 3.7309 | 3.6076 |
| LBPP | 162 | 3.6420 | 3.5093 |
| AIME24 | 30 | 3.5456 | 3.3864 |
| AIME25 | 30 | 3.4172 | 3.3192 |
| LiveCodeBench | 1,055 | 3.4154 | 3.3139 |
| Alpaca | 52,002 | 3.3504 | 3.2087 |
| Arena-Hard-v2 | 750 | 3.2091 | 3.0265 |
| SWE-Bench | 300 | 3.1914 | 2.9975 |
| Mean (12) | 3.8226 | 3.6864 |
RULER V2 at the 1M input configuration (50 prompts per partition, actual prompts 1,022,335–1,045,000 tokens):
| Partition | acc_len @ T=0 | acc_len @ T=1 |
|---|---|---|
| MK (multi-key) | 4.2665 | 3.9417 |
| MV (multi-value) | 4.2324 | 3.9666 |
| QA | 3.4938 | 3.2632 |
Long-context acceptance is flat on held-out 16K–64K agentic trajectories (67 rows, temperature 0): 3.592 (8–16K), 3.560 (16–32K), 3.534 (32K+).
Serving with SGLang
Requires a SGLang build with DSpark support
SGLANG_ENABLE_UNIFIED_RADIX_TREE=1 \
sglang serve --trust-remote-code \
--model-path thinkingmachines/Inkling-Small-NVFP4 --tp 8 \
--quantization modelopt_fp4 --attention-backend fa4 --page-size 128 \
--fp4-gemm-backend flashinfer_trtllm --moe-runner-backend flashinfer_trtllm_routed \
--enable-torch-symm-mem --mamba-radix-cache-strategy extra_buffer \
--mem-fraction-static 0.60 --swa-full-tokens-ratio 0.1 --mamba-full-memory-ratio 0.1 \
--max-running-requests 68 --reasoning-parser inkling --tool-call-parser inkling \
--skip-server-warmup --speculative-algorithm DSPARK \
--speculative-draft-model-path RadixArk/Inkling-Small-DSpark \
--speculative-draft-model-quantization unquant \
--speculative-dspark-block-size 7 \
--chunked-prefill-size 8192 --cuda-graph-max-bs-prefill 8192 \
--disable-flashinfer-autotune --host 0.0.0.0 --port 30000
Training Details
- Framework: SpecForge online distillation with hidden states captured from a frozen Inkling-Small target served by a colocated per-node TP4 SGLang engine; KV injection of fused target features into every draft layer with block-local bidirectional attention.
- Loss:
0.1 CE + 0.9 L1 distillation + 1.0 confidence BCE, 512 sampled anchors per sequence,block_size=7, within-block decay gamma4.