88plug/Gemma4-E4B-it-W4A16

Gemma4-E4B-W4A16

INT4 post-training quantization of google/gemma-4-e4b-it — Google's 4B-active multimodal MoE with 128 experts and hybrid sliding+global attention. Runs on a single RTX 3090 24GB or RTX 4090.

Quantized with AutoRound (iters=200, SignSGD rounding optimization) via llm-compressor. The LLM backbone is W4A16; vision tower, projector, and PLE layers remain BF16.

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At a Glance

Property	Value
Base model	google/gemma-4-e4b-it
Architecture	Sparse MoE, 128 experts, hybrid sliding+global attention + SigLIP vision
Quant method	AutoRound, iters=200
Quant scheme	W4A16 (4-bit weights, 16-bit activations)
Quant format	compressed-tensors (native vLLM)
Quantized	language_model.* — all Linear layers (attn + MLP)
Kept BF16	vision_tower, audio_tower, multi_modal_projector, embed_tokens_per_layer (PLE), per_layer_model_projection (PLE), lm_head, norms, embeddings
Disk size	~14 GB
Min GPU	1× RTX 3090 24GB

PLE layers kept at BF16

embed_tokens_per_layer and per_layer_model_projection implement Per-Layer Embeddings — ablations show catastrophic output degradation if quantized. Always excluded.

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Memory Requirements

Configuration	BF16	This Quant (W4A16)
Weights (disk/VRAM)	~28 GB	~14 GB
KV cache @ 32k ctx (fp8)	~2.0 GB	~2.0 GB
Total @ 32k ctx	~30 GB	~16 GB
Minimum GPU	A100 40GB	1× RTX 3090 24GB

The 4B active parameters (MoE) keep activation memory low. The full 26B+ parameter count still requires significant weight VRAM — W4A16 halves that requirement.

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Quick Start

Tested with vLLM v0.21.0 (vllm/vllm-openai:v0.21.0-cu129-ubuntu2404). Weights are in compressed-tensors format — vLLM detects and loads quantization automatically. No --quantization flag needed.

vLLM

docker run --gpus device=0 -p 8080:8080 \
  vllm/vllm-openai:v0.21.0-cu129-ubuntu2404 vllm serve \
  88plug/Gemma4-E4B-W4A16 \
  --kv-cache-dtype fp8 \
  --max-model-len 32768 \
  --gpu-memory-utilization 0.90

Weights are in compressed-tensors format — no --quantization flag needed.

Python client

from openai import OpenAI

client = OpenAI(base_url="http://localhost:8080/v1", api_key="x")

response = client.chat.completions.create(
    model="88plug/Gemma4-E4B-W4A16",
    messages=[{"role": "user", "content": "Explain sparse mixture-of-experts in two sentences."}],
    max_tokens=256,
)
print(response.choices[0].message.content)

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Quantization Design

The recipe targets all Linear modules in the LLM backbone with W4A16 (4-bit symmetric weight quantization, activations remain BF16). The following are excluded and kept at BF16:

Excluded pattern	Reason
lm_head	Output projection — quality-sensitive
.*embed_tokens$	Token embeddings
.*norm$	Layer norms
.*embed_tokens_per_layer.*	PLE: per-layer token embeddings — catastrophic if quantized
.*per_layer_model_projection.*	PLE: projection into hidden dim — catastrophic if quantized
.*vision_tower.*	SigLIP vision encoder — multimodal quality
.*audio_tower.*	Audio encoder — multimodal quality
.*multi_modal_projector.*	Cross-modal projector

All self_attn.{q,k,v,o}_proj and mlp.{gate,up,down}_proj layers across all transformer blocks are quantized to W4A16.

Calibration: 1024 samples — 512 from HuggingFaceH4/ultrachat_200k (chat) + 512 from wikitext-103-raw-v1 (text), max sequence length 2048.

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Competitor Comparables

Model	Source	Format	Compare angle
google/gemma-4-e4b-it	official	BF16	quality ceiling
RedHatAI/gemma-3n-E4B-it-quantized.w4a16	RedHatAI	compressed-tensors W4A16	same format, prior generation
88plug/Gemma4-E4B-W8A16	88plug	compressed-tensors W8A16	higher precision variant

First-to-market note: No compressed-tensors W4A16 quant found for gemma-4-e4b-it at release time. This is the first vLLM-native W4A16 for Gemma4 E4B.

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Benchmarks

Results pending.

Engine	Format	Batch	ctx	tok/s	TTFT p50	TTFT p99	VRAM
vLLM v0.21.0	W4A16 compressed-tensors	1	32k	—	—	—	—
vLLM v0.21.0	W4A16 compressed-tensors	8	32k	—	—	—	—
SGLang v0.5.8	BF16 (baseline)	1	32k	—	—	—	—
llama.cpp b9297	Q8_0 GGUF	1	32k	—	—	—	—
llama.cpp b9297	IQ4_XS GGUF	1	32k	—	—	—	—

Hardware: A6000 48 GB, CUDA 12.9, driver 570.

---

Quality Targets

Metric	Target
KL divergence vs BF16	< 0.014
MMLU recovery	≥ 99%

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SGLang Note

SGLang does not natively support compressed-tensors weights. To use SGLang, run the BF16 base model (google/gemma-4-e4b-it) directly:

docker run --gpus device=0 -p 30000:30000 \
  lmsysorg/sglang:v0.5.8-cu129 python -m sglang.launch_server \
  --model-path google/gemma-4-e4b-it \
  --tp 1 \
  --mem-fraction-static 0.85 \
  --port 30000

SGLang benchmark results above reflect BF16 baseline throughput, not this quant.

---

llama.cpp / GGUF

Convert from the BF16 base checkpoint — not from compressed-tensors weights. VLM requires a separate mmproj GGUF for image input.

python convert_hf_to_gguf.py google/gemma-4-e4b-it \
  --outfile Gemma4-E4B-BF16.gguf
python convert_hf_to_gguf.py google/gemma-4-e4b-it \
  --mmproj --outfile Gemma4-E4B-mmproj.gguf

llama-quantize Gemma4-E4B-BF16.gguf Gemma4-E4B-Q8_0.gguf Q8_0
llama-quantize --imatrix calibration_datav3.txt \
  Gemma4-E4B-BF16.gguf Gemma4-E4B-IQ4_XS.gguf IQ4_XS

llama-server \
  --model Gemma4-E4B-Q8_0.gguf \
  --mmproj Gemma4-E4B-mmproj.gguf \
  --n-gpu-layers 999 \
  --ctx-size 32768 \
  --port 8081

---

Citation

@misc{gemma4report,
  title  = {Gemma 4 Technical Report},
  author = {Google DeepMind},
  year   = {2025},
  url    = {https://huggingface.co/google/gemma-4-e4b-it}
}

---

About

88plug AI Lab produces production-grade compressed-tensors quantizations of frontier LLMs, VLMs, and omni models — built for native vLLM v0.21.0+ deployment with zero extra flags.

W8A16 — INT8 weights + BF16 activations. Near-lossless on any Ampere+ GPU. Runs where FP8 hardware cannot.

W4A16 — AutoRound with iters=200 and a mixed calibration corpus. Targets ≥ 99% MMLU recovery — the quality bar that makes W4A16 viable for production.

All weights are in compressed-tensors format. vLLM detects quantization automatically from quantization_config in config.json. No --quantization flag required.

Also available: Gemma4-E4B-it-W8A16 (INT8, ~5 GB) · Gemma4-E4B-it-W4A16 (INT4, ~14 GB)

Browse all releases → huggingface.co/88plug