glq 0.7.2

E8 lattice codebook quantization for LLM weights

GLQ — fit larger LLMs on smaller GPUs

E8-lattice post-training quantization for LLM weights: 2–8 bits/weight, served on vLLM · HuggingFace Transformers, with deterministic fused CUDA kernels and opt-in KV-cache compression (up to ~4×). Validated from 24 GB 3090-class GPUs (A10G, sm_86) to a 96 GB RTX PRO 6000 Blackwell (sm_120).

GLQ encodes each group of 8 weights as a 16-bit index into a 65,536-entry E8 lattice codebook; a Randomized Hadamard Transform makes the weights incoherent so Euclidean nearest-neighbour rounding is near-optimal under the Hessian-weighted proxy loss, and a fused CUDA kernel matmuls directly against the compressed indices — on the GPU serving path the dense weight is never materialized, so GPU memory drops with the compression ratio (CPU inference and a few architecture fallbacks dequantize instead).

What you get

• NEW in v0.7 — trellis (TCQ) codebook: single-stream decode at bf16 speed (176 vs 180 tok/s, SmolLM3-3B 4 bpw vs bf16, RTX PRO 6000 / vLLM) in a third of the memory, and good quality at 2–3 bpw. See Trellis codebook.
• 2–8 bpw, no group-size constraint, optional per-layer mixed precision.
• Serve anywhere — a vLLM plugin (weight + MoE + embedding + KV cache) and an HF Transformers integration. pip install glq, load, run.
• Small footprint — smallest of the ~4-bit quantizers we measured (vs AWQ / NVFP4 on a 26B); a 31B fits ≈16.5 GiB at 5 bpw where bf16 needs ≈58 GiB, with quality within noise of bf16 on our paired reasoning evals.
• Deterministic kernels — bit-identical logits across runs (reproducible lm-eval scoring / on-policy RL rollouts).
• Long context — opt-in E8 KV-cache compression (up to ~4× smaller KV → more context in the same VRAM).

Pick your path → run a model · fit a bigger model on your card · quantize your own · how GLQ compares · serve with vLLM · how it works

Quickstart

Run a pre-quantized model

pip install glq         # requires PyTorch ≥ 2.0

Python ≥ 3.10. Triton ships with PyTorch on CUDA and is used automatically. The CUDA C extension JIT-builds on first run (~30 s); CPU falls back to dequantize-then-matmul.

import glq.hf_integration  # registers GLQ with transformers
from transformers import AutoModelForCausalLM, AutoTokenizer

model = AutoModelForCausalLM.from_pretrained(
    "xv0y5ncu/SmolLM2-360M-Instruct-GLQ-block-diagonal-4bpw",
    device_map="auto",
)
tok = AutoTokenizer.from_pretrained("xv0y5ncu/SmolLM2-360M-Instruct-GLQ-block-diagonal-4bpw")
print(tok.decode(model.generate(
    **tok("The capital of France is", return_tensors="pt").to(model.device),
    max_new_tokens=20,
)[0], skip_special_tokens=True))

import glq.hf_integration registers quant_method="glq" with HF Transformers; from_pretrained then swaps nn.Linear for E8RHTLinear and uses the fused CUDA C kernel on inference. CPU falls back to a naive dequantize-then-matmul.

Or serve the fastest GLQ checkpoint on vLLM (the trellis-3INST decode — single-stream speed at bf16 parity, 1.9 GiB of weights):

pip install glq vllm      # glq ≥ 0.7.0 (trellis kernel storage layout)
vllm serve xv0y5ncu/SmolLM3-3B-trellis-3inst-4bpw-kernel --quantization glq

Available pre-quantized checkpoints

A few popular checkpoints (all on the xv0y5ncu HF org):

Repo	Base model	bpw	License	Footprint¹	Best for
Gemma-4-E4B-it-GLQ-4bpw	Gemma-4-E4B (8B, multimodal)	4.0	Apache 2.0	5.8 GiB	a capable model on an 8–12 GB card
SmolLM3-3B-trellis-3inst-4bpw-kernel	SmolLM3-3B	4.0 trellis	Apache 2.0	1.9 GiB	fastest GLQ decode — single-stream at bf16 parity
SmolLM3-3B-GLQ-block-diagonal-3.5bpw	SmolLM3-3B	3.5 mix	Apache 2.0	1.8 GiB	small + fast, fits anything
Gemma-4-12B-it-GLQ-5.0bpw	Gemma-4-12B	5.0 mix	Apache 2.0	6.9 GiB	12B on a 24 GB card
gemma-4-26B-A4B-it-GLQ-4bpw	Gemma-4-26B-A4B (MoE)	4.0	Apache 2.0	~15 GiB	best quality-per-GB (MoE)
Gemma-4-31B-it-GLQ-5.0bpw-mix3-8	Gemma-4-31B	5.0 mix	Apache 2.0	16.5 GiB	a 31B on one 24–32 GB card
Devstral-Small-2-24B-Instruct-GLQ-4bpw	Devstral-Small 24B	4.0²	Apache 2.0	~20.5 GiB	coding / agentic
SmolLM2-360M-Instruct-GLQ-block-diagonal-4bpw	SmolLM2-360M	4.0	Apache 2.0	0.25 GiB	tiny / CI demo

24 checkpoints total — the HF org also has SmolLM3 at 6 bpw, the Gemma-4 12B/31B/E4B family across 3–8 bpw (incl. e8p variants), and Nemotron. Per-model quality (MMLU-Pro / AIME, paired vs bf16) and throughput are in each model card and in How GLQ compares and Quality & footprint below.

_{¹ Footprint = resident weight memory after load (vLLM's Model loading took … GiB) — the figure that decides whether a model fits a 24/32 GB card. For current (block-diagonal) checkpoints it tracks the bpw budget — that is what lets a 31B fit one GPU. E8-KV compression doesn't change it; its payoff is an up-to-~4× smaller KV cache → more context / concurrency in the same VRAM.}

_{² Quantized before block-diagonal FHT became the quantizer default: power-of-2 FHT padding is stored as real bits, so the checkpoint holds more bits per weight than its nominal rate and the footprint is correspondingly larger than 4 bpw implies (the Nemotron repos share this). The -block-diagonal- repos above are true-to-label re-quants.}

Quantize your own model

pip install 'glq[quantize]'    # adds transformers, datasets, etc.

glq-quantize \
    --model HuggingFaceTB/SmolLM2-360M \
    --output ./smollm2-glq-4bpw \
    --bpw 4 \
    --nsamples 128 \
    --device cuda

Other bit-widths: pass --bpw 2 through --bpw 8 (fractional like 2.5 also works). glq-quantize --help lists every flag. For models that don't fit in system RAM use --streaming (loads one layer at a time from safetensors).

For mixed-precision allocation, run a two-pass flow: a profile pass writes a per-layer bpw_allocation.json, then a quantize pass applies it. See examples/quantize_mixed_precision.md.

Trellis (TCQ) quantization — the fastest-decoding GLQ format and the recommended pick at 2–4 bpw:

GLQ_TRELLIS_VARIANT=3inst glq-quantize \
    --model HuggingFaceTB/SmolLM3-3B \
    --output ./smollm3-trellis-3inst-4bpw \
    --codebook trellis --bpw 4 --nsamples 128

Always set GLQ_TRELLIS_VARIANT=3inst for new quantizations: the lookup-free 3INST decode is what the fused fast path is built for, and its quality measured equal-or-slightly-better than the legacy hyb lookup-table variant in our paired tests. (hyb remains the env default only for back-compat with existing hyb checkpoints.)

Trellis constraints differ from the shell/e8p paths: integer bpw only (2 / 3 / 4) — mixed precision and fractional rates are rejected rather than silently rounded — and the fused kernel needs layer dims with out % 32 == 0, in % 64 == 0 (standard transformer shapes qualify). Models with per-layer embeddings (Gemma-4 E2B/E4B) are handled automatically — the PLE table quantizes via the shell codebook (requires glq ≥ 0.7.2). Use --streaming for Gemma-4 family models. See Trellis codebook for details.

Docker image (NVIDIA GPU)

A prebuilt CUDA image ships everything needed to run GLQ models — glq, PyTorch, vLLM, transformers, and lm-eval on CUDA 12.8:

ghcr.io/cnygaard/glq-env:latest     # CUDA 12.8 bundle: glq + vLLM + transformers + lm-eval

Prerequisite — GPU access in Docker. You need an NVIDIA GPU plus the NVIDIA Container Toolkit installed on the host; that's what makes the --gpus all flag pass the GPU into the container. Verify it works:

docker run --rm --gpus all ghcr.io/cnygaard/glq-env:latest nvidia-smi

If that prints your GPU table, you're set. (No toolkit → --gpus errors with "could not select device driver".)

Produce output. Mount a host directory for the model cache (the image's HF_HOME is /cache/hf, so models persist across runs instead of re-downloading), then generate:

docker run --rm --gpus all \
    -v "$HOME/.cache/huggingface:/cache/hf" \
    ghcr.io/cnygaard/glq-env:latest \
    python -c '
import glq.hf_integration, torch                      # registers GLQ with HF
from transformers import AutoModelForCausalLM, AutoTokenizer
mid = "xv0y5ncu/SmolLM3-3B-GLQ-3.5bpw"
tok = AutoTokenizer.from_pretrained(mid)
model = AutoModelForCausalLM.from_pretrained(
    mid, device_map="cuda", torch_dtype=torch.float16)
ids = tok("The capital of France is", return_tensors="pt").to("cuda")
print(tok.decode(model.generate(**ids, max_new_tokens=20)[0],
                 skip_special_tokens=True))
'

Expected output:

The capital of France is Paris. It is located in the north of the country.

The first run downloads the model into the mounted cache; later runs reuse it. Swap mid for any GLQ checkpoint (see Available pre-quantized checkpoints).

Flag reference:

Flag	Why
--gpus all	binds all host GPUs into the container (needs the NVIDIA Container Toolkit). Use --gpus '"device=0"' to pick one.
-v "$HOME/.cache/huggingface:/cache/hf"	persists downloaded weights on the host (HF_HOME=/cache/hf inside) so they survive --rm.
--rm	remove the container when it exits (drop it to keep the container around).

Serving (vLLM) & an interactive shell. The image bundles vLLM, so you can serve an OpenAI-compatible endpoint — publish the port and mount the cache:

# Plain chat — the model ships its own chat template, so nothing extra needed:
docker run --rm --gpus all -p 8000:8000 \
    -v "$HOME/.cache/huggingface:/cache/hf" \
    ghcr.io/cnygaard/glq-env:latest \
    vllm serve xv0y5ncu/Gemma-4-E4B-it-GLQ-4bpw --max-model-len 64000

Tool-calling + thinking. Gemma-4's tool template is not in the model (its bundled chat_template.jinja is plain chat) and not in the vLLM pip wheel, so fetch it from vLLM's examples/ first, then mount it:

curl -fsSL https://raw.githubusercontent.com/vllm-project/vllm/v0.20.2/examples/tool_chat_template_gemma4.jinja \
    -o tool_chat_template_gemma4.jinja

docker run --rm --gpus all -p 8000:8000 \
    -v "$HOME/.cache/huggingface:/cache/hf" \
    -v "$PWD/tool_chat_template_gemma4.jinja:/work/tool.jinja:ro" \
    ghcr.io/cnygaard/glq-env:latest \
    vllm serve xv0y5ncu/Gemma-4-E4B-it-GLQ-4bpw \
        --max-model-len 64000 \
        --enable-auto-tool-choice \
        --tool-call-parser gemma4 \
        --reasoning-parser gemma4 \
        --chat-template /work/tool.jinja \
        --default-chat-template-kwargs '{"enable_thinking": true}'

Pass --chat-template the in-container mount path (/work/tool.jinja), not the host path. --default-chat-template-kwargs '{"enable_thinking": true}' defaults Gemma-4 reasoning on. The gemma4 parsers and all of these flags are accepted by the image's bundled vLLM 0.20.2 and the model loads; note that startup runs a multi-minute torch.compile + CUDA-graph capture before the endpoint is ready. See the vLLM Gemma-4 recipe for the full tool-calling / reasoning reference.

Image vs. pip: the image is a convenience bundle and may lag the PyPI package — pip install -U glq inside the container (or your own venv) always gets the newest release. The pip package is the source of truth; the image just saves you assembling a matching CUDA + vLLM + transformers stack.

For the long-context E8 KV-cache flags (GLQ_KV_*), pass them with -e and see E8 lattice cache / Inline-dequant E8 KV. The image's default command is a shell (docker run --rm -it --gpus all ghcr.io/cnygaard/glq-env:latest) if you'd rather poke around interactively.

How GLQ compares

GLQ sits next to the other post-training quantizers — AWQ, GPTQ, NVIDIA's NVFP4 (TensorRT Model Optimizer), and Unsloth's dynamic mixed-precision. They optimize for different things; here is the honest layout.

	GLQ	AWQ	GPTQ	NVFP4 (ModelOpt)	Unsloth dynamic
Bits / weight	2–8 + mixed	4 (grouped)	3–4 (grouped)	~4 (W4A4)	mixed 2–8 (selective)
Group-size constraint	none	g64/g128	g64/g128	—	—
Core method	E8 lattice + RHT + LDLQ	activation-aware scale	block error-feedback	FP4 + per-tensor scale	per-layer bit allocation
Footprint at ~4-bit	smallest (no per-group scales/zeros)	+ group scales/zeros	+ group scales/zeros	+ FP8 scales	varies
Speed on Blackwell	W4A16; single-stream at bf16 parity (trellis 3INST, 3B measured)	W4A16 (Marlin)	W4A16 (Marlin)	fastest at batch (native FP4)	n/a (GGUF)
Serving stack	vLLM · HF	vLLM · HF · TRT	vLLM · HF · TRT	vLLM · TRT-LLM	llama.cpp / Ollama (GGUF)
KV-cache compression	built-in (~4×)	—	—	fp8 KV	(llama.cpp KV)
Bit-exact deterministic kernels	yes	—	—	—	—
Fine-tuning (QLoRA)	—	—	—	—	yes

_{A "—" means the feature is absent or not advertised by that method — we have not tested the other methods for those properties.}

Where each wins — pick by your constraint, not by a single "best":

• GLQ — the smallest footprint of the ~4-bit methods we measured, the widest bit-range (2–8) with per-layer mixed precision, deterministic kernels, and built-in KV compression. The pick when you are memory-bound — fit a bigger model or longer context on a 24–32 GB card — and serve on vLLM / HF.
• NVFP4 (ModelOpt) — fastest on Blackwell (native FP4 tensor cores). The pick when you have a Blackwell GPU with memory to spare and want raw decode speed; it trades a larger footprint than GLQ for that speed.
• AWQ / GPTQ — mature, ubiquitous 4-bit weight-only with fast Marlin kernels. The safe default on any GPU when a ~4-bit footprint is enough and you don't need <4 bpw.
• Unsloth dynamic — selective mixed-precision for the GGUF / llama.cpp stack, plus a strong QLoRA fine-tuning story. A different target (CPU/edge/Ollama, or training) than GLQ's GPU serving — GLQ also does per-layer mixed precision, but for the vLLM/HF stack.

Where GLQ speed stands after v0.7.1 (measured, SmolLM3-3B on an RTX PRO 6000, vLLM 0.25): single-stream (B=1) trellis-3INST decode is at bf16 parity — 176 vs 180 tok/s — while using a third of the weight memory. At batch, bf16 still leads (2,423 vs 4,887 tok/s at concurrency 32) — the batched GEMM is the remaining gap. The shell/e8p codebooks decode slower than trellis; their draw is the 2–8 bpw range and mixed precision. A weight-quantization method's headline win remains footprint — the freed VRAM as KV / longer-context headroom, and fitting models bf16 can't — but at 4 bpw trellis the single-user speed cost of that footprint is now ~zero on the hardware we measured.

Matched 4-bit head-to-head (measured)

Numbers behind the matrix: GLQ vs AWQ vs NVFP4 on one base model (gemma-4-26B-A4B-it, an MoE), all at ~4-bit so footprint is directly comparable, on a single RTX PRO 6000 Blackwell (vLLM 0.23, seed 0, thinking mode). bf16 is the uncompressed ceiling.

Method	bits	Weights, exact on disk¹	MMLU-Pro n=60²	AIME-2026 n=30²
bf16 (ceiling)	16	~50 GB	91.7%	90.0%
GLQ 4 bpw	4.0	14.97 GB	93.3%	90.0%
AWQ 4-bit	~4.25	17.19 GB	86.7%	83.3%
NVFP4 (W4A4)	~4	18.78 GB	86.7%	90.0%

GLQ has the smallest footprint, the top MMLU-Pro, and matches the bf16 ceiling on hard reasoning — AIME-2026 GLQ 90.0% = bf16 90.0% = NVFP4 90.0% > AWQ 83.3% (GLQ reproduces bf16's 27/30 exactly, at <1/3 the footprint); MMLU-Pro is saturated (all 86.7–93.3%, inside the ±8% n=60 band → a tie). The trade is decode speed: GLQ ran the same 30-problem AIME in 58 min vs ~24 min for AWQ/NVFP4 and ~32 min for bf16 — its W4A16 kernel is L2-codebook-gather-bound on Blackwell, where NVFP4's native FP4 tensor cores, AWQ's Marlin, and even bf16 all decode faster. So GLQ's win is footprint + quality, not speed — the pick when you are memory-bound. Full tables, truncations, chain lengths, and caveats: benchmarks/_quant_compare_gemma4_26b.md.

_{¹ Exact safetensors weight bytes summed from tensor headers (tower-independent — all three ship the identical 1.15 GB vision tower); loaded footprints track this ordering (GLQ ~14.0 < AWQ 15.6 < NVFP4 17.1 GiB). ² Thinking mode, single-sample pass@1, seed-fixed subsets; n=60 MMLU-Pro 95% CI ≈ ±8%, n=30 AIME ≈ ±15% — a fidelity comparison on one model / one GPU, not a leaderboard. NVFP4 is W4A4 (4-bit activations) and defaults to fp8 KV, a speed edge the W4A16 methods don't take; calibration differs per vendor. The paired GLQ-vs-bf16 view (incl. AIME-2024) is in Quality & footprint below.}

Trellis 3INST vs bf16 vs NVFP4 (measured)

The same exercise for the trellis-3INST format on a dense model: SmolLM3-3B, one RTX PRO 6000 Blackwell, vLLM 0.25.0, glq 0.7.1. Speed = vllm bench sweep serve (random 128-in/256-out, ignore-eos, seed 42, mean of 3 runs); quality = wikitext-2 PPL + AIME-2026 in thinking mode (32k budget, 8 samples/problem, avg@8).

	GLQ trellis-3INST 4 bpw	bf16	NVFP4 (W4A4)¹
Weights on disk	1.9 GB	5.8 GB	2.5 GB
Decode, 1 stream (tok/s)	176	180	301
Decode, 32 streams (tok/s)	2,423	4,887	7,600
PPL (wikitext-2)	9.23	9.12	n/a²
AIME-2026 avg@8 (thinking)	41.7%	47.5%	32.5%
240-generation batch job, wall-clock³	52 min	36 min	32 min

The read: at 4 bpw trellis, GLQ decodes single-stream at bf16 parity in a third of the memory, and keeps most of the reasoning quality (−5.8 pts AIME vs bf16) where this NVFP4 checkpoint's 4-bit activations cost −15 pts. NVFP4 is decisively faster — but its FP4 tensor cores exist only on Blackwell; on the 24 GB 3090-class (sm_86) / 4090-class (sm_89) cards GLQ targets, NVFP4 cannot use FP4 hardware, while GLQ's fp16-mma kernels have no Blackwell dependency (core GLQ kernels validated on sm_86 / sm_89 / sm_120; the trellis kernels to date on sm_120).

_{¹ Firworks/SmolLM3-3B-nvfp4, a community w4a4 checkpoint — results are scoped to it, not to NVFP4 at large. ² The checkpoint does not load in HF transformers; quality measured via vLLM (AIME row). ³ 30 AIME problems × 8 samples at up to 32k tokens each, launched as one batch — fixed load/compile overhead and the low-concurrency straggler tail compress the steady-state speed ratios (3.1× at c=32 becomes 1.6× on the real job).}

Quality & footprint

SmolLM3-3B at matched 4.5 bpw vs GPTQ

Blackwell RTX PRO 6000, 128 calibration samples, lm-evaluation-harness limit=200/task (GSM8K n=500, MMLU 50/subtask). GLQ 4.5 bpw uses two-pass mixed allocation (91 layers @ 4 bpw + 161 @ 5 bpw, avg 4.64 bpw).

Task	bf16	GLQ 4.5 bpw	GPTQ W4 g128
ARC-challenge (acc_n)	0.490	0.475	0.420
ARC-easy (acc_n)	0.745	0.735	0.695
HellaSwag (acc_n)	0.660	0.660	0.675
MMLU (acc)	0.617	0.603	0.589
TruthfulQA mc2	0.529	0.545	0.515
WinoGrande	0.655	0.660	0.670
WikiText-2 ppl ↓	10.67	10.90	11.33
GSM8K flex (n=500)	0.722	0.738	0.688
IFEval prompt-strict	0.310	0.310	0.285
IFEval prompt-loose	0.325	0.330	0.295
IFEval inst-strict	0.478	0.472	0.453
IFEval inst-loose	0.494	0.491	0.469

GLQ beats GPTQ on 10/12 metrics. WikiText-2 ppl gap to bf16: +2.2 % (GLQ) vs +6.2 % (GPTQ). GSM8K flex matches bf16; GPTQ drops 0.034.

Small models: SmolLM2-360M-Instruct at 4 bpw

GPTQ requires a group-size dividing the hidden dim; SmolLM2-360M's hidden=960 is not divisible by 128, forcing group_size=64 (~4.5 eff bpw) and losing quality. GLQ has no group-size constraint.

Method	bpw stored	5-task avg	% of bf16
bf16	16.0	0.557	100 %
GLQ 4-bit block-diagonal (current)	4.0	—	**97.9 %**¹
GLQ 4-bit legacy (padded)	~6.4 eff¹	0.555	99.6 %
GPTQ W4 (g64)	~4.5	0.486	87.2 %

5-task = ARC-e, HellaSwag, PIQA, WinoGrande, LAMBADA; 128 calibration samples; L40S. GPTQ's LAMBADA collapses to 0.346; GLQ preserves 0.508.

_{¹ The original "4 bpw" checkpoint predates block-diagonal FHT and stored its power-of-2 padding as real bits — effectively ~6.4 bits/weight, so its 99.6 % was earned with extra storage. The true-4-bpw re-quant (SmolLM2-360M-Instruct-GLQ-block-diagonal-4bpw) scores 97.9 % of bf16 on the same 5 tasks (paired GLQ/bf16 runs on the vLLM stack) — still well clear of GPTQ. The group-size constraint on GPTQ applies regardless.}

Gemma-4 family — GLQ vs bf16, paired (thinking mode)

Each GLQ checkpoint was run head-to-head against its bf16 base on the same questions, in thinking mode (these are reasoning models), on a single RTX PRO 6000 Blackwell with vLLM 0.23. These are small-n fidelity comparisons (95% CI ≈ ±8% MMLU-Pro, ±15% AIME), single-sample pass@1 — not leaderboard scores.

Model (GLQ vs bf16)	bpw	Footprint GLQ / bf16	MMLU-Pro n=60	AIME-2024 n=30
Gemma-4-31B-it	5.0 mix	16.5 / 57.9 GiB	90.0% vs 86.7%	90.0% vs 86.7%
Gemma-4-26B-A4B-it (MoE)	4.0	~15 / ~50 GiB	93.3% vs 91.7%	93.3% vs 93.3%
Gemma-4-12B-it	5.0 mix	6.9 / 24 GiB	81.7% vs 78.3%	83.3% vs 93.3%†

On these runs GLQ is within noise of bf16 — ahead on MMLU-Pro for all three, ahead/tied on AIME-2024 for the 31B and 26B-A4B. †At n=30 the 12B AIME-2024 gap (bf16 +3 items) is not statistically significant; likewise the 31B's AIME-2026 (GLQ 83.3% vs bf16 90.0%, bf16 +2 items). Footprint is the consistent win — a 31B in 16.5 GiB fits one 24–32 GB card where bf16 (~58 GiB) needs three. See each model card for the full paired tables, thinking budgets, and caveats.

GLQ also decodes at near-bf16 throughput on memory-bound GPUs — e.g. SmolLM3-3B 3.5 bpw ran at ~94% of bf16 tok/s (single-stream and batched) on an L40S — because the compressed weights cut DRAM bandwidth enough to offset the dequant cost.

How it works

1. E8 lattice codebook. 65,536 vectors from the first seven shells of the E8 lattice in 8 dimensions. Each 8-weight group of the weight matrix is encoded as one 16-bit index into this codebook (so the primary stage is 2 bpw). For 3–8 bpw, additional 8-bit (256-entry) or 16-bit (E8) residual codebooks refine the primary's reconstruction error.

2. Randomized Hadamard Transform. Random sign flips followed by Fast Walsh-Hadamard Transform rotate both weights and Hessian. After RHT the Hessian is approximately diagonal, so plain Euclidean nearest-neighbour in the codebook is near-optimal under the Hessian-weighted proxy loss.

3. LDLQ error feedback. Block-LDL decomposition of the Hessian drives a sequential sweep — GPTQ-style, but over 8-D blocks instead of scalar columns. Each block's quantization error propagates forward to correct downstream blocks.

4. Fused inference kernels. Custom CUDA C and Triton kernels read codebook indices from HBM, gather the 8-D vectors from the L2-cached 1 MB codebook, and accumulate the matmul directly — the dense weight matrix is never materialized. GPU memory savings scale with the compression ratio.

KV cache compression

GLQ ships two KV cache compressors. Either is opt-in — default behaviour is unchanged.

INT8 cache (HF transformers)

Per-channel absmax INT8 plus a small fp16 residual window for recent tokens — KIVI-style. Halves the KV memory at long context.

import glq.hf_integration
from glq.kv_cache import GLQQuantizedCache

cache = GLQQuantizedCache(model.config)
output = model.generate(**inputs, max_new_tokens=200,
                         past_key_values=cache)

Requires transformers >= 4.45. No external dependencies.

E8 lattice cache (vLLM, v0.3.0+)

Drops vLLM's paged KV cache to as little as ~25 % of fp16 footprint (recipe-dependent) using the same E8 lattice quantizer used for weights. Two fused Triton kernels (read-side dequant-gather, write-side scatter) keep decode within ~20 % of un-fused throughput.

Measured on Gemma-4-E4B-it, RTX PRO 6000 Blackwell, vLLM 0.20:

	fp16 baseline	E8 lattice
KV cache capacity @ 27.9 GiB	303,984 tokens	1,221,232 (4.02×) at e8_relaxed:1
mmlu_pro n=240 accuracy	71.25 %	71.25 % (bit-identical) at e8_relaxed:2
NIAH passkey @ ctx=16k / 32k / 64k / 130k	—	40/40 at e8_relaxed:2 (full 128k window)
cudaLaunchKernel per decode	110,659	71,619 (−35 %) at e8_relaxed:2

Note the capacity row was measured with the e8_relaxed:1 recipe and the quality rows with e8_relaxed:2 — the recipes trade capacity for fidelity, so pick one and measure both for your model.

Activation:

GLQ_KV_QUANT=e8_relaxed:2 \
GLQ_KV_E8_SIDECAR=1 GLQ_KV_E8_SIDECAR_READ=1 \
GLQ_KV_E8_COMPRESSED_ALLOC=1 \
GLQ_KV_E8_FUSED_GATHER=1 GLQ_KV_E8_FUSED_WRITE=1 \
vllm serve google/gemma-4-E4B-it

The envs above use the workspace path: GLQ pre-decompresses the referenced K/V into a scratch buffer, then calls vLLM's stock attention. Because that buffer is built with a data-dependent block_table.unique(), glq auto-forces cudagraph_mode=PIECEWISE for this path (you'll see [glq_vllm] E8 KV active → cudagraph_mode forced ... to PIECEWISE at startup; --enforce-eager is no longer required as of v0.3.5). Weight-only GLQ still uses the default FULL_AND_PIECEWISE. The v0.5 inline-dequant path below lifts the PIECEWISE restriction and is the recommended path for long-context / KV-bound serving.

Validated end-to-end on Gemma-4-E4B-it / Gemma-4-31B-it on vLLM 0.20.x.

Inline-dequant E8 KV (default in v0.5.1)

The workspace path above pre-decompresses K/V into a scratch buffer that vLLM's attention then re-reads — pure overhead, since each K/V vector is read exactly once. The inline-dequant path instead dequantizes the compressed E8 K/V inside a forked Triton attention kernel (an 8-point FHT butterfly for the inverse Hadamard, plus flash-decoding KV-split for long-context occupancy). There is no workspace, and — because the read/write hooks are host-sync-clean — the FULL CUDA graph captures the whole decode, eliminating the per-token eager-dispatch overhead that dominated E8-KV decode.

As of v0.5.1 this is the default for the E8-KV path — the standard bundle is all you need (no extra flag):

GLQ_KV_QUANT=e8_relaxed:2 \
GLQ_KV_E8_SIDECAR=1 GLQ_KV_E8_SIDECAR_READ=1 \
GLQ_KV_E8_COMPRESSED_ALLOC=1 \
GLQ_KV_E8_FUSED_GATHER=1 GLQ_KV_E8_FUSED_WRITE=1 \
vllm serve xv0y5ncu/SmolLM3-3B-GLQ-3.5bpw

Opt out with GLQ_KV_E8_INLINE_DEQUANT_V3=0 (reverts to the 65 K workspace path) or GLQ_KV_E8_FORCE_PIECEWISE=1 (keeps inline but disables the FULL decode graph).

Decode throughput, SmolLM3-3B-GLQ-3.5bpw, RTX PRO 6000 Blackwell, vLLM 0.20.2 — inline vs the pre-v0.5 E8-KV path (workspace, PIECEWISE):

	E8 KV before v0.5	inline (v0.5)
decode B=1	~15 tok/s	38 (2.5×)
decode B=4	~37	127 (3.4×)
decode @ ctx=16k, B=1	~15	36 (2.4×)

The speedup is the FULL-graph capture the inline path unlocks; it brings E8-KV decode to roughly weight-only parity. On Gemma-4-E4B-it (large heads, already compute-bound) decode is roughly unchanged, but quality and long-context behaviour match.

Quality is neutral. On SmolLM3 the inline-FULL path is bit-identical to PIECEWISE (MMLU-Pro n=120 and NIAH-16k match exactly). On Gemma-4 it lands within vLLM's own run-to-run greedy non-determinism — MMLU-Pro n=120, thinking, 16384-token budget: PIECEWISE 0.742 vs inline-FULL 0.750 (a smaller gap than two PIECEWISE runs differ from each other), NIAH-16k 10/10 both.

Scope. It covers the 4 bpw KV recipe (e8_relaxed:2); other recipes automatically fall back to the workspace path. It requires the Triton attention backend (auto-forced when E8 KV is active). Validated across the consumer GPU lineup — A10G (sm_86, 3090-class, 24 GB), L40S (sm_89, 4090-class), and RTX PRO 6000 Blackwell (sm_120, 5090-class): the kernels compile and NIAH-16k + MMLU are correct on all three, and FULL-vs-PIECEWISE is quality-neutral on Blackwell (the consumer-card runs are shorter FULL-only smokes). Opt out per above.

Advanced

CUDA-graph decode wrapper

The B=1 autoregressive decode path is Python-dispatch-bound in eager mode. CUDAGraphWrapper captures the fixed-shape decode and replays it; benchmarks below are on SmolLM3-3B 3.5bpw, L40S.

Mode	GLQ 3.5 bpw	bf16
Eager	25 tok/s	40
CUDA graph	37 tok/s	40

from glq.cuda_graph import CUDAGraphWrapper
wrapper = CUDAGraphWrapper(model)
logits = wrapper(input_ids)   # first call captures; replays after

The wrapper falls back to eager for variable shapes (prefill, batch>1, extra kwargs). For 24B models the matmul is compute-bound at B=1, so graphs don't help (Devstral-24B GLQ 4 bpw: 6.6 tok/s eager vs 6.4 graphed).

Tuning vLLM CUDA-graph capture sizes (v0.3.4+)

vLLM 0.20 captures both FULL model-forward graphs (single replay per fixed shape) and PIECEWISE subgraphs split at attention. The default capture set is derived from max_num_seqs * 2, so a single-sequence harness only gets FULL captures for [1, 2]. For batched serving, raise the list explicitly:

from vllm import LLM
llm = LLM(model="xv0y5ncu/Gemma-4-E4B-it-GLQ-4bpw",
          compilation_config={
              "cudagraph_capture_sizes": [1, 2, 4, 8, 16],
          })

Measured impact on Gemma-4-E4B-it-GLQ-4bpw, RTX PRO 6000 Blackwell, 256-token decode:

Mode	B=1 tok/s	B=4 tok/s (total)
Eager	14.4	35.0
Piecewise + default capture [1, 2]	39.4	132.7
Piecewise + capture [1, 2, 4, 8, 16]	40.0	157.3 (+18.5 %)

At B=1 the FULL graph was already captured (no change). At B=4 the extended list keeps the FULL graph active where the default degenerated to PIECEWISE-only, recovering ~6 tok/s per sequence.

Cost: ~10-20 MB VRAM per captured shape on 3B / E4B models (vLLM prints the total at "Graph capturing finished in N s, took X GiB"). On 24-31B models budget ~100-200 MB per shape. Capture time is ~1 s per shape, one-time at LLM init.

Bit widths

bpw	Primary	Residual stages
2	16 b	—
3	16 b	+ 8 b
4	16 b	+ 16 b
5	16 b	+ 16 b + 8 b
6	16 b	+ 16 b + 16 b
7	16 b	+ 16 b + 16 b + 8 b
8	16 b	+ 16 b + 16 b + 16 b

One global scale per layer; no group-size parameter. Non-power-of-2 hidden sizes use block-diagonal FHT (v0.2.9+) — e.g. 2688 is decomposed as 2048 + 512 + 128 so on-disk storage matches the nominal rate exactly.

The table above applies to the shell and e8p codebooks. The trellis codebook is a single K-bit trellis code with no residual stages — integer 2 / 3 / 4 bpw only.

Trellis codebook (--codebook trellis) — QTIP-derived TCQ

--codebook trellis replaces the per-8-weight lattice lookup with trellis-coded quantization (TCQ) over 256-weight sequences, following QTIP (Tseng et al., 2024): a Viterbi search encodes each row against a tail-biting trellis, so neighbouring weights share state and the effective codebook is exponentially larger than a flat lookup at the same rate. In our SmolLM3-3B tests it is GLQ's best format at 2–4 bpw — at 2 bpw it clearly beats the e8p codebook (PPL 11.74 vs 13.21) — and at 4 bpw its decode is GLQ's fastest (single-stream at bf16 parity, see the measured table).

Variants. GLQ_TRELLIS_VARIANT=3inst decodes each 16-bit trellis state arithmetically (a hash + two fp16 halves — "3 instructions", no lookup table), which is what the fused fast path is built around; the default hyb uses a 512-entry lookup table and exists for back-compat with earlier hyb checkpoints. Quality measured equal-or-slightly-better for 3INST in our paired tests — use 3INST for new quants.

What the v0.7.1 kernels do (the 129 → 179 tok/s single-stream jump): the input Hadamard transform and fp16 cast run inside every decode block instead of as separate 1-block launches; the five lowest FHT butterfly stages run as warp shuffles; and the per-shard output transforms of fused QKV / gate-up layers batch into single launches. All bit-exact — wikitext-2 PPL is unchanged to the fourth decimal across the entire optimization series. Runtime opt-outs, should you ever need the unfused paths: GLQ_TRELLIS_FUSE_INPUT=0, GLQ_TRELLIS_BATCH_OUT_RHT=0.

Storage layout. Trellis checkpoints store indices in the decoder-native "kernel" layout (trellis_layout: "kernel" in the config) — loading them requires glq ≥ 0.7.0; older versions abort with a layout error rather than decode garbage. Rates are integer 2 / 3 / 4 bpw with a single trellis code per layer (no residual stages, no mixed precision — both are rejected at quantize time). Quantization cost is the Viterbi encode: ~35 min for a 3B on one GPU (CUDA-graph-cached).

E8P codebook (--codebook e8p) — derivative of QuIP#

--codebook e8p is derivative work that ports the E8P codebook and its tensor-core decode kernels from QuIP# (Tseng et al., 2024). It swaps the default E8-shell codebook for QuIP#'s 2-bit E8P (padded-D̂8) grid decoded on tensor cores (mma.sync GEMV), plus residual vector quantization for the higher rates. The port is self-contained (no quiptools dependency); full credit and the citation are in Acknowledgments.

bpw	RVQ recipe (stages)	added per stage
2	[E8P]	16-bit E8P (primary)
3	[E8P, E81B]	+ 8-bit E81B residual
4	[E8P, E8P]	+ 16-bit E8P residual
5	[E8P, E8P, E81B]	+ 8-bit E81B
6	[E8P, E8P, E8P]	+ 16-bit E8P
7	[E8P, E8P, E8P, E81B]	+ 8-bit E81B
8	[E8P, E8P, E8P, E8P]	+ 16-bit E8P

Each E8P stage is a 16-bit tensor-core decode (mma.sync GEMV, +2 bpw); odd bit-widths end in a single 8-bit E81B residual (WMMA lookup-matmul, +1 bpw).

glq-quantize --model HuggingFaceTB/SmolLM2-360M --output ./out \
    --codebook e8p --bpw 4 --nsamples 128

The entire linear — input RHT → E8P tensor-core decode (all RVQ stages) → ×Wscale → output RHT — runs as a single fused CUDA op (glq_fused_linear_e8p_cuda), so vLLM captures B=1 decode in a FULL CUDA graph exactly like the default path (HF inference is supported too). On SmolLM3-3B 4 bpw (RTX PRO 6000 Blackwell, vLLM 0.23) that fused op runs B=1 decode at ~85 tok/s; collapsing the per-linear dispatch into one opaque op is what makes cudagraph a win here — the equivalent unfused multi-op path is ~7× slower under capture. The full 2–8 bpw range serves on both HF and vLLM as of v0.6.7 (the 5–8 bpw N-stage decode landed there); the fused op is bit-exact against the unfused reference across all of 2–8 bpw (decode reproduces the quantize-side weight to ~66–68 dB SQNR per bit-width).

Devstral-24B tokenizer

transformers 5.x auto-routes Mistral/Devstral models through mistral_common, which rejects the standard tokenizer.json. Use PreTrainedTokenizerFast explicitly:

from huggingface_hub import snapshot_download
from transformers import AutoModelForCausalLM, PreTrainedTokenizerFast

path = snapshot_download("xv0y5ncu/Devstral-Small-2-24B-Instruct-GLQ-4bpw")
tok = PreTrainedTokenizerFast(tokenizer_file=f"{path}/tokenizer.json")
tok.pad_token, tok.eos_token, tok.bos_token = "<pad>", "</s>", "<s>"
model = AutoModelForCausalLM.from_pretrained(
    "xv0y5ncu/Devstral-Small-2-24B-Instruct-GLQ-4bpw",
    device_map="cuda", dtype="float16",
)

examples/inference_hf.py includes a load_tokenizer() helper that handles this automatically.

transformers compatibility

For models ≤ 1B parameters use transformers >= 5.0. Transformers 4.57.x has a weight-loading bug that produces garbage output for small GLQ models. Larger models (3B+) work with both 4.x and 5.x.

Inference kernels

glq/inference_kernel.py + glq/csrc/glq_cuda.cu provide CUDA C and Triton kernels that compute Y = X @ dequant(W)^T without materializing the weight matrix. Each kernel iterates over N/8 codebook blocks per output row, gathers 8-D vectors from the L2-cached codebook, and accumulates the matmul directly against indices.

Path	When	Notes
CUDA C Tensor Core	B ≥ 2 (prefill)	inline PTX mma.sync against codebook-loaded registers; 3-5× faster than Triton
CUDA C split-K matvec	B = 1 (decode)	4 rows/warp + __shfl_xor_sync reduction; 2.7× faster than Triton
CUDA C shared-mem FHT	RHT step	double-buffered butterfly; low 5 stages as warp shuffles (v0.7.1)
Trellis 3INST fused linear	trellis checkpoints, B = 1	lookup-free decode with the input RHT + cast computed in-block — one kernel per linear (v0.7.1)
Shard-batched output RHT	trellis, fused QKV / gate-up	per-shard output transforms in one grid.y launch (v0.7.1)
Triton fallback	no ninja, or n_pad > 32 768	always available

Bit-exact determinism. Every kernel reduces partial sums in a fixed order (scratch-buffer split-K or in-block reduction) instead of atomicAdd across k-splits, so running the same prompt at B=1 decode or B=8 prefill produces identical logits across runs — required for reproducible lm-eval scoring and on-policy RL rollouts.

Direct kernel access:

from glq.inference_kernel import glq_dequant_matmul
y = glq_dequant_matmul(x, Qidxs, codebook, Wscale,
                       Qidxs2=Qidxs2, codebook2=codebook2,
                       inv_resid_scale=inv_rs)  # 3/4 bpw two-stage

Architecture

glq/
  codebook.py          # E8ShellCodebook: enumeration, encode/decode
  hadamard.py          # Fast Walsh-Hadamard Transform
  rht.py               # Randomized Hadamard Transform
  ldlq.py              # Block-LDL quantization with error feedback
  quantize_model.py    # Full model pipeline + CLI
  quantized_linear.py  # E8RHTLinear: drop-in nn.Linear replacement
  inference_kernel.py  # Triton kernels + CUDA dispatch
  csrc/glq_cuda.cu     # CUDA C kernels (split-K matvec, TC, FHT)
  hf_integration.py    # HuggingFace Transformers integration
  kv_cache.py          # INT8 quantized KV cache
  cuda_graph.py        # B=1 decode wrapper
glq_vllm/              # vLLM integration: weight + KV cache (v0.3.0+)

Acknowledgments

This project builds on QuIP# (Tseng et al., 2024). The default E8-shell pipeline is inspired by its Hadamard-incoherence + lattice-codebook formulation, and the optional --codebook e8p path is derivative work that ports QuIP#'s E8P (padded-D̂8) codebook and its tensor-core decode / residual kernels — the grid_packed_abs codebook plus the decode_matvec_e8p, decompress_packed_e8p, and E81B lookup-matmul kernels in glq/csrc/glq_e8p.cu. All credit for the E8P codebook and those kernels belongs to the QuIP# authors; this repository is an independent port, not an official QuIP# release. See the QuIP# repository for the paper and citation.

The --codebook trellis path is likewise derivative of QTIP (Tseng et al., 2024): the tail-biting trellis formulation, the hybrid lookup codebook, the "3INST" lookup-free decode idea, and the bit-unpack structure of the kernels in glq/csrc/glq_trellis.cu all originate there — GLQ grafts them onto its own RHT + LDLQ pipeline and fused-linear kernel architecture. All credit for TCQ and the 3INST decode belongs to the QTIP authors; see the QTIP repository for the paper and citation.

Other foundations:

• E8 lattice: Korkin & Zolotarev (1872); Gosset (1900); Conway & Sloane, Sphere Packings, Lattices and Groups; Viazovska (2016) — sphere-packing optimality in 8 dimensions.
• Block-feedback quantization: GPTQ (Frantar et al., 2022).
• INT8 KV cache: KIVI (Liu et al., 2024).

License

GNU General Public License v3.0 (GPL-3.0). See LICENSE.