OneCompression is a Python package for compressing large language models.

github.com/FujitsuResearch/OneCompression
OneComp homepage screenshot

About OneComp

OneComp is an open-source Python package for compressing large language models with post-training quantization. It runs from the command line as onecomp or from Python with Runner.auto_run, detecting available GPU VRAM, assigning per-layer bit widths, quantizing, evaluating, and saving the result.

It includes quantization methods such as QEP, LPCD, AutoBit, JointQ, MDBF, and block-wise distillation, along with LoRA fine-tuning, rotation preprocessing, vLLM plugins for serving, and GGUF export for llama.cpp/Ollama with Hugging Face Hub upload. GGUF export supports Llama and Qwen2 architectures, and rotation preprocessing supports Llama and Qwen3 architectures.

Key features

  • Automatic VRAM-based per-layer bit-width assignment via AutoBit
  • Quantization error propagation to subsequent layers with QEP
  • Serve quantized models with vLLM plugins for DBF, Mixed-GPTQ
  • Convert models to GGUF v3 format for llama.cpp and Ollama
  • LoRA fine-tuning of quantized models for accuracy recovery
  • Block-wise distillation against FP16 teacher at block granularity
Best for: Researchers and developers who need to quantize LLMs to fit available GPU memory.
Good for
  • Single-command quantization via CLI or Python Runner
  • Multiple quantization methods including QEP, LPCD, JointQ, and MDBF
  • Integrations for vLLM serving, GGUF export, and Hugging Face Hub upload
Watch out for
  • GGUF export supports only Llama and Qwen2 architectures
  • Rotation preprocessing supports only Llama and Qwen3 architectures

OneComp at a glance

Type
Open-source project
Pricing
Not confirmed. Check the site
Open source
Yes · Source code
Language
English
Last checked
Oct 5, 2026 · Online when checked
Listed
Oct 5, 2026

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OneComp FAQ

How do I start automatic quantization?
Run `onecomp meta-llama/Llama-2-7b-hf` from the command line, or call `Runner.auto_run(model_id="meta-llama/Llama-2-7b-hf")` from Python.
How does AutoBit choose bit widths?
It estimates the target bit width from available VRAM and assigns per-layer bit widths to minimize quantization error under the memory budget.
How can quantized models be used for inference?
Serve them with vLLM using built-in plugins for DBF and Mixed-GPTQ methods, or convert them to GGUF v3 format for llama.cpp and Ollama.
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