Gemma 4 26B-A4B-it -- Native TQ3 Checkpoint (12 GB)

Native 3-bit TurboQuant checkpoint of google/gemma-4-26B-A4B-it. Weights are stored as packed 3-bit indices with per-group norms. 12 GB on disk instead of 52 GB.

This checkpoint is designed for GPUs that cannot fit the original 52 GB BF16 weights. Tested on L40S 48GB ($0.91/hr) and H100 80GB.

Usage

Requires turboquant-plus-vllm and transformers >= 5.5.0 (Gemma 4 support).

pip install turboquant-plus-vllm@git+https://github.com/varjoranta/turboquant-vllm.git
pip install 'transformers>=5.5'

from turboquant_vllm import load_tq3_model

model, tokenizer = load_tq3_model("varjosoft/gemma-4-26B-A4B-it-TQ3-native")

chat = [{"role": "user", "content": "What is the capital of Finland?"}]
text = tokenizer.apply_chat_template(chat, tokenize=False, add_generation_prompt=True)
inputs = tokenizer(text, return_tensors="pt").to("cuda")

import torch
with torch.no_grad():
    output = model.generate(**inputs, max_new_tokens=100, do_sample=False)
print(tokenizer.decode(output[0], skip_special_tokens=True))

How It Works

The custom loader (load_tq3_model) creates the model skeleton on a meta device (zero memory), loads packed weights directly to GPU, and decompresses on-the-fly during each forward pass. Linear layers become compressed wrapper modules. MoE expert weights use chunked decompression (8 experts at a time) to limit GPU memory peak.

This is NOT a standard HuggingFace checkpoint. It cannot be loaded with AutoModelForCausalLM.from_pretrained(). You must use load_tq3_model() from the turboquant-plus-vllm library.

Results

Metric	Value
Checkpoint size	12 GB (vs 52 GB BF16)
GPU memory for weights	13.5 GB
Compression ratio	4.3x
Quality	Same packed weights as runtime TQ3, which scores 4.79/5 on our 20-scenario benchmark
Load time	~6 seconds (H100), ~12 seconds (L40S)
Minimum GPU	L40S 48GB tested. 24 GB-class feasible subject to KV cache and runtime overhead

Quality validated by spot-check on H100 80GB: correct on factual recall, arithmetic, science, and Finnish language prompts.

What This Checkpoint Contains

model-00001-of-00003.safetensors through model-00003-of-00003.safetensors: packed 3-bit weight indices (.tq_packed) and per-group norms (.tq_norms) for compressed layers; FP16 tensors for embeddings, layer norms, and biases
tq_config.json: compression parameters (bits=3, group_size=128, seed=42)
config.json, tokenizer.json, tokenizer_config.json: standard HuggingFace model config and tokenizer

How It Was Made

from turboquant_vllm.checkpoint import save_tq3_checkpoint

save_tq3_checkpoint("google/gemma-4-26B-A4B-it", "./gemma4-tq3-native")
# CPU only, ~60 GB RAM, ~2 minutes. No GPU needed.

Each weight tensor is read from the original safetensors one at a time (lazy loading), compressed with TQ3 (Walsh-Hadamard rotation + Lloyd-Max codebook + norm correction), and saved as packed uint8 indices + float32 norms. Non-weight tensors (embeddings, norms, biases) are kept as FP16.

Algorithm

Inspired by TurboQuant (Zandieh, Daliri, Hadian, Mirrokni; ICLR 2026). Our implementation uses a Gaussian Lloyd-Max codebook as an approximation of the paper's distortion-rate framework. Norm correction stores original_norm / reconstruction_norm per group to fix magnitude shrinkage at 3-bit.

Citation

@inproceedings{zandieh2026turboquant,
  title={TurboQuant: Online Vector Quantization with Near-optimal Distortion Rate},
  author={Zandieh, Amir and Daliri, Majid and Hadian, Majid and Mirrokni, Vahab},
  booktitle={International Conference on Learning Representations},
  year={2026}
}

Compressed by Varjosoft Oy using turboquant-plus-vllm.