### What does this PR do? Type of change: refactor (no behaviour change) The five GGML IQ CUDA encoders were five copies of the same search. IQ2_XS and IQ2_XXS shared 139 of their roughly 150 lines of encoder and launcher code, and IQ2_S 113 of them. IQ1_S and IQ1_M had the same structure with a different choice space. Every scaled packer also validated its scales twice, in the `ggml.cpp` pybind wrapper and again in the CUDA entry point. This PR keeps **one encoder per family**, as two templates: - **`iq2_family.cuh`** for IQ2_XS, IQ2_XXS and IQ2_S. The grid sits in shared memory, the 16 local scales are scored per group, and each vector then takes its best entry under the chosen scale. A format supplies its group shape, whether it stores seven sign bits and recovers the eighth from parity, and a `store()` that writes the chosen entries, sign masks and local scales into its layout. - **`iq1_family.cuh`** for IQ1_S and IQ1_M, over the shared ternary grid. Each group picks one of `kChoices` options. With `kSharedShift` the option also fixes the ±1/8 delta (IQ1_S: `shift * 8 + local`); otherwise each vector picks its own (IQ1_M). IQ1_S's scale kernel now writes FP16 scales, so both IQ1 formats take the same input. Each format file is now one `Format` struct, holding its layout constants and `store()`, plus its entry point: 58–100 lines each. Validation lives once in `common.cuh`, as `check_pack_inputs` and `check_scaled_pack_inputs`. `ggml.cpp` binds the CUDA entry points directly instead of through five wrappers. **The kernel sources shrink from 1,536 to 1,241 lines** (+665 / −960). This is the first of two PRs. #2604 builds on it: it adds CUDA decoders as a `decode()` next to each format's `store()`, and makes export reuse fake quant's packed payloads. ### Testing **Nothing changes in the output.** Before the refactor I hashed 40 outputs: 5 formats × float32/bfloat16/float16/float64 inputs × encode and decode, on a weight with zero, tiny, oversized and non-finite blocks. All 40 hash the same afterwards. **Encode speed is unchanged.** Old and new were timed alternately for four rounds, in both orders, on an idle RTX PRO 6000 with a 5632×2048 weight. They were within 1% for every format: IQ1_S 37.6 / 37.6 ms, IQ1_M 37.0 / 37.0, IQ2_XXS 10.9 / 10.9, IQ2_XS 11.9 / 12.0, IQ2_S 15.5 / 15.4. - `tests/gpu/torch/quantization/test_iq_formats_cuda.py`, `test_iq1_s_cuda.py`, `test_iq2_xs_cuda.py`: **49 passed** - **Validation reports the same errors in the same order.** Over 5 formats × 8 combinations of bad arguments (devices, dtype, width, grid shape, scales dtype, length and sign), every first error matches main's. - `tests/gpu/_extensions/test_torch_extensions.py`: the validation-message tests pass. #2515's two Q8_0 tests fail identically on a clean `main` on this GPU. - IQ unit tests (`test_ggml_backend.py`, `test_iq_formats.py`, `test_convert_hf_config.py`, `test_presets.py`, `test_export_weight.py`): **173 passed** ### Before your PR is "*Ready for review*" - Is this change backward compatible?: ✅ Same bindings, messages and bytes. - If you copied code from any other sources or added a new PIP dependency, did you follow guidance in `CONTRIBUTING.md`: ✅ No new code sources or dependencies. - Did you write any new necessary tests?: N/A. A refactor with no behaviour change, verified by the hashes above and the existing GPU tests. - Did you update Changelog?: N/A - Did you get Claude approval on this PR?: ❌ Not yet run. ### Additional Information Merge order: **this** → #2604 (pack each IQ weight once and decode on CUDA). 🤖 Generated with [Claude Code](https://claude.com/claude-code) <!-- This is an auto-generated comment: release notes by coderabbit.ai --> ## Summary by CodeRabbit * **Bug Fixes** * Quantization now checks that inputs and grids are CUDA tensors on the same device, with compatible shapes. Scaled formats also validate scale type, shape, and finite, non-negative values. * **Improvements** * IQ1 and IQ2 formats share common encoding paths while retaining their format-specific output layouts. <!-- end of auto-generated comment: release notes by coderabbit.ai --> --------- Signed-off-by: Chenjie Luo <chenjiel@nvidia.com> Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
NVIDIA Model Optimizer (referred to as Model Optimizer, or ModelOpt) is a library comprising state-of-the-art model optimization techniques including quantization, pruning, Neural Architecture Search (NAS), distillation, speculative decoding and sparsity to accelerate models.
[Input] Model Optimizer currently supports inputs of a Hugging Face, PyTorch or ONNX model.
[Optimize] Model Optimizer provides Python APIs for users to easily compose the above model optimization techniques and export an optimized quantized checkpoint. Model Optimizer is also integrated with NVIDIA Megatron-Bridge, Megatron-LM and Hugging Face Accelerate for training required inference optimization techniques.
[Export for deployment] Seamlessly integrated within the NVIDIA AI software ecosystem, the quantized checkpoint generated from Model Optimizer is ready for deployment in downstream inference frameworks like SGLang, TensorRT-LLM, TensorRT, or vLLM. The unified Hugging Face export API now supports both transformers and diffusers models.
Latest News
- [2026/09/16] End-to-end W4A4 NVFP4 + QAD tutorial for Qwen3.6-35B-A3B: NVFP4 W4A4 PTQ plus quantization-aware distillation, reaching up to 1.30x vLLM throughput over BF16 and 3.1x smaller checkpoints while recovering the accuracy W4A4 costs.
- [2026/09/09] BLOG: Improving NVFP4 Accuracy with Local-Hessian Weight Scales
- [2026/08/24] BLOG: AutoQuantize: A Fast Automatic Mixed-Precision Assignment
- [2026/08/17] BLOG: Developing Nemotron 3.5 Lightning NVFP4 with QAD Using NVIDIA Model Optimizer: Learn how quantization-aware distillation recovers accuracy from aggressive NVFP4 quantization while reducing model size and increasing throughput.
- [2026/06/26] BLOG: Creating the NVIDIA Nemotron 3 Ultra NVFP4 Checkpoint with NVIDIA Model Optimizer: How we quantized Nemotron 3 Ultra (550B) to NVFP4 with Model Optimizer — up to 5.9× higher decode-heavy inference throughput than GLM-5.1 754B FP4 while matching BF16 accuracy. NVFP4 Checkpoint on Hugging Face.
- [2026/05/27] End-to-end Optimization tutorial for Nemotron-3-Nano-30B-A3B: Pruning + two-phase distillation + FP8 quantization achieving 2.6× vLLM throughput and 2.6× memory reduction.
- [2026/05/13] Puzzletron: A new algorithm for heterogeneous pruning & NAS of LLM and VLM models.
- [2026/04/15] Customer story: Domyn compresses Colosseum-355B → 260B using ModelOpt's Minitron pruning + distillation
- [2026/03/17] Customer story: Bielik.AI builds Bielik Minitron 7B (33% smaller, 50% faster, 90% quality retained) using ModelOpt's Minitron pruning + distillation
- [2026/03/11] Model Optimizer quantized Nemotron-3-Super checkpoints are available on Hugging Face for download: FP8, NVFP4. Learn more in the Nemotron 3 Super release blog. Check out how to quantize Nemotron 3 models for deployment acceleration here
- [2026/03/11] NeMo Megatron Bridge now supports Nemotron-3-Super quantization (PTQ and QAT) and export workflows using the Model Optimizer library. See the Quantization (PTQ and QAT) guide for FP8/NVFP4 quantization and HF export instructions.
- [2025/12/11] BLOG: Top 5 AI Model Optimization Techniques for Faster, Smarter Inference
- [2025/12/08] NVIDIA TensorRT Model Optimizer is now officially rebranded as NVIDIA Model Optimizer.
- [2025/10/07] BLOG: Pruning and Distilling LLMs Using NVIDIA Model Optimizer
- [2025/09/17] BLOG: An Introduction to Speculative Decoding for Reducing Latency in AI Inference
- [2025/09/11] BLOG: How Quantization Aware Training Enables Low-Precision Accuracy Recovery
- [2025/08/29] BLOG: Fine-Tuning gpt-oss for Accuracy and Performance with Quantization Aware Training
- [2025/08/01] BLOG: Optimizing LLMs for Performance and Accuracy with Post-Training Quantization
- [2025/06/24] BLOG: Introducing NVFP4 for Efficient and Accurate Low-Precision Inference
- [2025/05/14] NVIDIA TensorRT Unlocks FP4 Image Generation for NVIDIA Blackwell GeForce RTX 50 Series GPUs
- [2025/04/21] Adobe optimized deployment using Model-Optimizer + TensorRT leading to a 60% reduction in diffusion latency, a 40% reduction in total cost of ownership
- [2025/04/05] NVIDIA Accelerates Inference on Meta Llama 4 Scout and Maverick. Check out how to quantize Llama4 for deployment acceleration here
- [2025/03/18] World's Fastest DeepSeek-R1 Inference with Blackwell FP4 & Increasing Image Generation Efficiency on Blackwell
- [2025/02/25] Model Optimizer quantized NVFP4 models available on Hugging Face for download: DeepSeek-R1-FP4, Llama-3.3-70B-Instruct-FP4, Llama-3.1-405B-Instruct-FP4
- [2025/01/28] Model Optimizer has added support for NVFP4. Check out an example of NVFP4 PTQ here.
- [2025/01/28] Model Optimizer is now open source!
Previous News
- [2024/10/23] Model Optimizer quantized FP8 Llama-3.1 Instruct models available on Hugging Face for download: 8B, 70B, 405B.
- [2024/09/10] Post-Training Quantization of LLMs with NVIDIA NeMo and Model Optimizer.
- [2024/08/28] Boosting Llama 3.1 405B Performance up to 44% with Model Optimizer on NVIDIA H200 GPUs
- [2024/08/28] Up to 1.9X Higher Llama 3.1 Performance with Medusa
- [2024/08/15] New features in recent releases: Cache Diffusion, QLoRA workflow with NVIDIA NeMo, and more. Check out our blog for details.
- [2024/06/03] Model Optimizer now has an experimental feature to deploy to vLLM as part of our effort to support popular deployment frameworks. Check out the workflow here
- [2024/05/08] Announcement: Model Optimizer Now Formally Available to Further Accelerate GenAI Inference Performance
- [2024/03/27] Model Optimizer supercharges TensorRT-LLM to set MLPerf LLM inference records
- [2024/03/18] GTC Session: Optimize Generative AI Inference with Quantization in TensorRT-LLM and TensorRT
- [2024/03/07] Model Optimizer's 8-bit Post-Training Quantization enables TensorRT to accelerate Stable Diffusion to nearly 2x faster
- [2024/02/01] Speed up inference with Model Optimizer quantization techniques in TRT-LLM
Install
To install stable release packages for Model Optimizer with pip from PyPI:
pip install -U nvidia-modelopt[all]
Model Optimizer will download and install additional third-party open source software projects. Review the license terms of these open source projects before use.
To install from source in editable mode with all development dependencies or to use the latest features, run:
# Clone the Model Optimizer repository
git clone git@github.com:NVIDIA/Model-Optimizer.git
cd Model-Optimizer
pip install -e .[dev]
You can also directly use NVIDIA container images, which have Model Optimizer pre-installed:
nvcr.io/nvidia/pytorch:<version>-py3nvcr.io/nvidia/nemo:<version>nvcr.io/nvidia/tensorrt-llm/release:<version>
Before pulling and using the container images, please review their respective license terms. Make sure to upgrade Model Optimizer to the latest version as described above. Visit our installation guide for more fine-grained control on installed dependencies or for alternative docker images and environment variables to setup.
Techniques
| Technique | Description | Getting started | Examples |
|---|---|---|---|
| Post Training Quantization | Compress model size by 2x-4x, speeding up inference while preserving model quality! | [Start here] | [HF LLMs / VLMs] [Megatron-Bridge LLMs / VLMs] [Diffusers] [ONNX] [Windows] |
| Quantization Aware Training / Distillation | Refine accuracy of quantized models even further with a few training steps! | [Start here] | [Hugging Face] [Megatron-Bridge] |
| Pruning | Reduce your model parameters or memory footprint and accelerate inference by removing unnecessary weights! | [Start here] | [General] [Megatron-Bridge] |
| Distillation | Reduce deployment model size by teaching small models to behave like larger models! | [Start here] | [Hugging Face] [Megatron-Bridge] [Megatron-LM] |
| Speculative Decoding | Train draft modules to predict extra tokens during inference! | [Start here] | [Hugging Face] [Megatron-LM] |
| Sparsity | Efficiently compress your model by storing only its non-zero parameter values and their locations | [Start here] | [Hugging Face] |
Pre-Quantized Checkpoints
- Ready-to-deploy checkpoints [🤗 Hugging Face - Nvidia Model Optimizer Collection]
- Deployable on TensorRT-LLM, vLLM and SGLang
- More models coming soon!
Resources
Model Support Matrix
| Model Type | Support Matrix |
|---|---|
| LLM / VLM Quantization | View Support Matrix |
| Diffusers Quantization | View Support Matrix |
| ONNX Quantization | View Support Matrix |
| Windows Quantization | View Support Matrix |
| Quantization Aware Training | View Support Matrix |
| Pruning | View Support Matrix |
| Distillation | View Support Matrix |
| Speculative Decoding | View Support Matrix |
Deprecation Policy
Model Optimizer follows a structured approach to managing deprecated features:
- Communication: Deprecation notices are documented in the Changelog. Deprecated items include source code statements indicating deprecation timing, with runtime warnings issued upon use.
- Migration Period: Since Model Optimizer is still pre-1.0, we provide a 1-release (~1-month) migration period after deprecation. During this window, deprecated features continue functioning while issuing warnings.
- Scope: The policy addresses both complete deprecations (entire APIs removed) and partial ones (specific parameters removed while methods remain).
- Removal: Following the migration period, deprecated elements are removed in alignment with semantic versioning standards, potentially including breaking changes in minor version updates while Model Optimizer remains in 0.x.
Citation
If you use NVIDIA Model Optimizer in your research, please cite it as follows:
@misc{nvidia-modelopt,
author = {{NVIDIA Corporation}},
title = {{NVIDIA Model Optimizer}},
howpublished = {\url{https://github.com/NVIDIA/Model-Optimizer}},
year = {2024--2026},
note = {GitHub repository}
}
Contributing
Model Optimizer is now open source! We welcome any feedback, feature requests and PRs. Please read our Contributing guidelines for details on how to contribute to this project.
AI Agents
ModelOpt's agent skills can be installed from this repository and used in any workspace.
Claude Code
claude plugin marketplace add https://github.com/NVIDIA/Model-Optimizer.git
claude plugin install modelopt@modelopt
Codex
codex plugin marketplace add https://github.com/NVIDIA/Model-Optimizer.git
Then open /plugins, select the modelopt marketplace, and install modelopt.
Contributors can also use the skills directly from a checkout. See the
agent tooling notes.
Top Contributors
Happy optimizing!
