Qwen3.8 STQ — Quantization Frontier

One base model. One pinned toolchain. Four measured GGUF tiers.

Research · Evidence · Base model

Model family

This repository publishes controlled GGUF quantizations of Qwen/Qwen3.8-27B. Every tier was produced from the same BF16 GGUF with the same pinned llama.cpp build and importance matrix. This is a measurement study, not a new codec claim.

tier size physical bpw Top-1 WikiText-2 PPL best fit
IQ3_XXS 11.19 GB 3.3273 86.00% 7.3318 smallest practical text deployment
IQ4_XS 15.08 GB 4.4862 85.63% 6.9023 stronger perplexity at low memory
Q4_K_M 16.55 GB 4.9219 86.50% 6.8611 balanced default
Q5_K_M 19.23 GB 5.7201 86.88% 6.8498 closest measured quality to BF16

Point llama.cpp at the first shard; the remaining shards are discovered automatically.

Measured quality

Top-1 accuracy by quantization tier

BF16 baseline: 696/800 = 87.00%. Two independent paid runs reproduced the same file hash and item-level correctness vector. Results use a preregistered 800-item stratified MMLU+ARC letter-logprob harness, seed 22, 10,000 paired bootstrap samples, exact two-sided McNemar, and a +2.00 pp non-inferiority margin.

arm correct accuracy loss vs BF16 95% CI of loss McNemar p verdict
IQ3_XXS 688/800 86.00% 1.000 pp [−0.375, 2.375] pp 0.215 undetermined
IQ4_XS 685/800 85.63% 1.375 pp [0.500, 2.375] pp 0.007 significant loss on this set
Q4_K_M 692/800 86.50% 0.500 pp [−0.375, 1.375] pp 0.388 non-inferior
Q5_K_M 695/800 86.88% 0.125 pp [−0.750, 1.000] pp 1.000 non-inferior

Perplexity is monotone with bit width even though Top-1 is not. The IQ4/IQ3 ordering is therefore treated as a property of this 800-item sample, not a broad quality claim.

BF16 token agreement · unmatched protocols

Pacific and Unsloth BF16 next-token Top-1 agreement by quantization tier; corpora and protocols are not matched
nominal tier Pacific agreement agreements Wilson 95% CI Unsloth chart estimate direct delta
IQ3_XXS 72.000% 576/800 [68.789, 75.001]% ≈89.2% not calculated
IQ4_XS 87.625% 701/800 [85.162, 89.729]% ≈94.0% not calculated
Q4_K_M 88.500% 708/800 [86.103, 90.529]% ≈95.8% not calculated
Q5_K_M 90.750% 726/800 [88.543, 92.568]% ≈97.2% not calculated

Pacific agreement is measured from the completed 800-item runs: for each fixed MMLU+ARC prompt, the candidate's raw pre-sampling Top-1 token ID is compared with the BF16 Top-1 token ID. All five evidence files share the same ordered item fingerprint and pinned llama.cpp commit. This is one next-token position per prompt; it is not task accuracy or generation quality.

The Unsloth provider chart also reports BF16 next-token Top-1 agreement, but on a different provider KL-divergence corpus and protocol. Its values above were digitized from the published PNG and rounded to 0.1 pp because no numeric result table is published. The green bars are estimates, and the cross-provider differences are not valid quality deltas. A valid provider comparison still requires running both GGUFs against the same 800 item IDs and scoring code.

The figure is generated with Microsoft Flint Chart 0.5.1 using its Swiss theme. Reproducibility assets: measured result · calculation script · Flint input · compiled Vega-Lite spec · render script.

LiveCodeBench v6 · preliminary

Execution grading is pending. The value below is a hard upper bound, not a measured pass@1 score. No extraction failure was manually repaired.

stage result status
Raw generation 1,055 / 1,055 complete; zero empty raw responses
Official code extraction 918 / 1,055 87.01% extraction coverage
Extraction failures 137 / 1,055 retained as automatic failure candidates
Measured pass@1 pending sandboxed execution has not run
Hard pass@1 ceiling ≤87.01% best possible before execution grading
BF16 model-card reference 90.3% upstream, unmatched protocol

The best-case cross-protocol gap to the upstream BF16 reference is ≤−3.29 pp. The actual gap can only be larger. A matched BF16 run is required before claiming quantization retention.

LiveCodeBench v36 reproducibility profile
setting value
Dataset release_v6, 1,055 tasks
Task-ID SHA-256 6108435b7b39af8ffaf11dc6c206adb6fa2ae92d6f01ea58ae0134ba345fd47a
LiveCodeBench commit 28fef95ea8c9f7a547c8329f2cd3d32b92c1fa24
Runtime Tesla V100-SXM2-16GB, NVIDIA driver 580.173.02
llama.cpp 580e88d8b7dece7099d9b62323521d0254ff3615, build 10716
Sampling n=1, temperature 1.0, top-p 0.95, top-k 20, min-p 0.0
Penalties presence 0.0, repetition 1.0
Thinking enabled; 8,192-token reasoning budget
Limits 16,384 output tokens, 32,768 context, 1,200 s timeout
Server full GPU offload, FP16 KV, batch 512, micro-batch 128, parallel 1
API local OpenAI-compatible endpoint, Jinja chat template

The initial 15-item pilot produced two reasoning-only truncations under an 8,192-token total limit. A 16,384-token limit with unrestricted reasoning reproduced the failure. v36 separated an 8,192-token reasoning budget from final-answer capacity; its pilot passed 15/15. Thirteen normally terminated pilot responses were retained, the two truncated responses were regenerated, and 1,040 remaining prompts ran under v36.

Machine-readable audit →

Throughput

Measured on one A100 80GB with full GPU offload, prompt 512 / generation 128, five runs.

arm prompt tok/s generation tok/s peak VRAM
BF16 2,423.5 26.9 50.1 GB
IQ3_XXS 1,232.9 50.9 11.3 GB
IQ4_XS 1,338.5 57.1 14.9 GB
Q4_K_M 1,288.1 48.2 16.3 GB
Q5_K_M 1,248.0 44.2 18.7 GB

Pinned build

component revision
Base model Qwen/Qwen3.8-27B@1d4bf0f2ff6012fd82039f2fa52739d0dd7c60c0
llama.cpp 580e88d8b7dece7099d9b62323521d0254ff3615
Conversion convert_hf_to_gguf.py --outtype bf16 --no-mtp
Importance matrix shared; 20 realized chunks from the pinned 96-record corpus

The reproducible BF16 text GGUF SHA-256 is 03ab7ad49486af2f111ed8d7616a0f485f9c5032bd6bc2419b84bb3b90f3930f. The BF16 text model and full run evidence are hosted in the artifact dataset.

Usage

llama-cli \
  -m Q4_K_M/qwen38-27b-q4_k_m-00001-of-00003.gguf \
  -p "Explain why low-bit perplexity and task accuracy can disagree."

For vision input, add:

--mmproj mmproj/qwen38-27b-mmproj-bf16.gguf

Merge split shards with llama-gguf-split --merge if a single file is required.

Scope

  • MMLU+ARC Top-1, WikiText-2 PPL, and A100 throughput are measured results.
  • BF16 next-token agreement is measured at 800 fixed prompt positions from the preserved pre-sampling token IDs; it is not a generation-quality score.
  • LiveCodeBench 87.01% is an ungraded ceiling, not pass@1.
  • The older v0.26 MLP-only IQ3 result is not pooled with this full-model GGUF study.
  • This repository is a research measurement, not a universal deployment recommendation.

License

Apache-2.0, inherited from Qwen/Qwen3.8-27B.

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