Qwen3.8-27B-Int4-AutoRound

INT4 (W4A16) quantization of Qwen/Qwen3.8-27B produced with Intel AutoRound (0.15.0.dev, git main), exported in the auto_round format (GPTQ-compatible packing, quant_method: auto-round).

19 GB on disk vs 55.6 GB BF16 (2.9× smaller). Tuned and validated on 2× Intel Arc B70 (Battlemage, 32 GB) with vLLM's XPU backend, TP=2.

Quantization recipe

• bits=4, group_size=128, sym=True, iters=200, nsamples=128, seqlen=2048, calibration dataset NeelNanda/pile-10k, signed-rounding tuning (AutoRound default).
• Kept in BF16 (unquantized):
  • vision tower (model.visual.*) — weights are bit-identical to the base model
  • lm_head (untied, 1.27B params)
  • GDN linear-attention low-rank gates (linear_attn.in_proj_a / in_proj_b)
  • MTP speculative-decoding tensors — preserved unmodified in model_extra_tensors.safetensors for stacks that can use them
• 400 of 607 candidate linear layers quantized; per-layer exclusions are recorded in quantization_config.extra_config and mirrored in quantization_config.json.

Quality — measured against an FP8 baseline of the same base model

Both sides served by the same vLLM build, identical harness, greedy decoding, thinking disabled:

Eval	FP8 (online per-tensor W8A16)	This model (INT4)
HumanEval pass@1	92.7	93.9
HumanEval+ pass@1	90.9	89.6
GSM8K 5-shot (raw-completions harness)	38.4	43.2

Coding performance is statistically indistinguishable from the FP8 baseline (n=164, ±2.3 pts). The low GSM8K absolutes on both sides are an artifact of the raw few-shot completions harness (roughly half the responses unparseable for both models); the A/B delta favors this model. Text-only validation — the (unmodified) vision tower was not exercised in these evals.

Speed — 2× Intel Arc B70 32GB, vLLM XPU backend, TP=2

Metric	FP8 online quant	This model
Single-stream decode	32.9 tok/s	51.9 tok/s (+58%)
Batched, 32 concurrent	167 tok/s	206 tok/s (+23%)
Median TTFT (1K-token prompt)	431 ms	478 ms

Serving

Docker (recommended on Intel Arc B-series)

The tuned serving stack this model was validated with ships as a Docker image: cyspiegel/vllm-xpu-b70 (vLLM XPU fork + custom GDN kernels, MTP speculative decoding, in-image Intel compute runtime). It downloads this checkpoint on first start and derives the fast GPTQ-kernel variant automatically:

docker run -d --name vllm-b70 --privileged --device /dev/dri --ipc host --shm-size 16g \
  -p 8000:8000 \
  -v ~/.cache/huggingface:/root/.cache/huggingface -v /path/to/models:/models \
  -e MODEL=CySpiegel/Qwen3.8-27B-Int4-AutoRound \
  cyspiegel/vllm-xpu-b70:latest

Serves an OpenAI-compatible API on :8000 as model name Qwen3.8-27B-Int4 with MTP speculative decoding enabled (PRESET=int4-mtp; use PRESET=int4 to disable it). Measured in-container on 2× Arc B70, TP=2: 57 tok/s single-stream greedy (13.1 ms/token), 199 tok/s at 32 concurrent. Compose file and all knobs: docker/b70/ in the CySpiegel/vllm-intel fork.

Plain vLLM

vllm serve <this-repo> --tensor-parallel-size 2 --language-model-only \
  --reasoning-parser qwen3 --enable-auto-tool-choice --tool-call-parser qwen3_coder

The checkpoint loads through vLLM's auto-round (INC) integration out of the box, and through Hugging Face transformers with the auto-round package installed.

Intel XPU tip: the fastest serve path in our testing was vLLM's GPTQ kernel (int4_gemm_w4a16). The packed tensors are already GPTQ-layout, so a config-only rewrite enables it: set quantization_config to {"quant_method": "gptq", "bits": 4, "group_size": 128, "sym": true, "desc_act": false, "lm_head": false} (keep the shards unchanged). On Arc B70 this was +58% decode throughput over FP8 online quantization; the unmodified auto-round path also works but benchmarked slower at high concurrency on XPU.

Provenance and license

Base model by the Qwen team, Apache-2.0. This derivative keeps the same license and carries the original LICENSE file. Quantized with AI assistance (Claude Code) on 2026-08-24; recipe selection, benchmarks, and validation as described above. No fine-tuning was performed — weights differ from the base model only by INT4 rounding-tuned quantization of the listed layers.