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Chenjie Luo
1d21ab9e29
## Summary - DeepSeek PTQ (`examples/deepseek/ptq.py`) now defaults to native top-k routing during MoE calibration. The previous all-tokens-to-all-experts path (`CalibMoe`) is preserved behind a new `--calib_all_experts` flag. - After `mtq.quantize`, `fixup_moe_expert_amax` syncs every expert's `input_quantizer.amax` (w1/w2/w3) to the per-layer global peer max via `dist.all_reduce(MAX)` across EP ranks. `weight_quantizer.amax` stays per-expert; any uncalibrated expert is filled by computing amax over the dequantized FP8 weight. - `mtq.print_quant_summary` is now also written to `<output_path>/.quant_summary.txt`, mirroring `llm_ptq/hf_ptq.py`. ## Why Forcing all tokens through every expert doubled calibration time and inflated `input_quantizer.amax` for cold-routing experts with outliers they never see at inference. The new flow matches the inference distribution, runs roughly 2x faster, and mirrors the `layer_sync_moe_local_experts_amax` semantics that mtq runs automatically for `QuantSequentialMLP`-derived MoEs. ## Validation (DeepSeek-V3.2-Exp, MP=8, NVFP4_DEFAULT_CFG) Compared `_amax_baseline` (CalibMoe) vs `_amax_synced` (new default): - All 44,544 expert weight amaxes bit-identical. - Attention, shared experts, gate: identical. - Expert `w1.input` and `w3.input` (shared MoE block input): identical. - Expert `w2.input` (post-SiLU gated, expert-specific): synced to layer-wide peer max — 99.3% are larger than baseline (median 11.4x) since peer-max captures the worst-case outlier from any expert in the layer; 0.7% are smaller. This is the same trade-off `set_expert_quantizer_amax` makes for HF MoEs in `unified_export_hf.py`. ## Test plan - [x] DeepSeek-V3.2-Exp MP8 PTQ with default flags — completes in ~7 min (vs ~27 min with CalibMoe), produces `_amax_synced/` consistent with the comparison above. - [x] DeepSeek-V3.2-Exp MP8 PTQ with `--calib_all_experts` — produces `_amax_baseline/` identical (other than rounding) to the prior `CalibMoe`-default behavior. - [x] `.quant_summary.txt` written under `output_path` on rank 0. <!-- This is an auto-generated comment: release notes by coderabbit.ai --> ## Summary by CodeRabbit * **New Features** * Added a `--calib_all_experts` option to enable an alternate PTQ calibration mode; default remains top-k routing with a post-calibration per-layer peer-max synchronization and a compute fallback for uncalibrated experts. * **Documentation** * Clarified default and alternate calibration behaviors and added note about generation of a `.quant_summary.txt` summary file. <!-- end of auto-generated comment: release notes by coderabbit.ai --> --------- Signed-off-by: Chenjie Luo <chenjiel@nvidia.com> Signed-off-by: Chenjie Luo <108829653+cjluo-nv@users.noreply.github.com>
NVIDIA Model Optimizer (referred to as Model Optimizer, or ModelOpt) is a library comprising state-of-the-art model optimization techniques including quantization, distillation, pruning, 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
- [2026/03/11] 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>nvcr.io/nvidia/tensorrt:<version>-py3
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 | Examples | Docs |
|---|---|---|---|
| Post Training Quantization | Compress model size by 2x-4x, speeding up inference while preserving model quality! | [LLMs] [diffusers] [VLMs] [onnx] [windows] | [docs] |
| Quantization Aware Training | Refine accuracy even further with a few training steps! | [Hugging Face] | [docs] |
| Pruning | Reduce your model size and accelerate inference by removing unnecessary weights! | [General] [Megatron-Bridge] | |
| Distillation | Reduce deployment model size by teaching small models to behave like larger models! | [Megatron-Bridge] [Megatron-LM] [Hugging Face] | [docs] |
| Speculative Decoding | Train draft modules to predict extra tokens during inference! | [Megatron] [Hugging Face] | [docs] |
| Sparsity | Efficiently compress your model by storing only its non-zero parameter values and their locations | [PyTorch] | [docs] |
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 Quantization | View Support Matrix |
| Diffusers Quantization | View Support Matrix |
| VLM 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 |
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.
Top Contributors
Happy optimizing!