### What does this PR do? Type of change: new feature Adds `modelopt.torch.utils.mlflow.MlflowRunLogger`, a reusable helper for recording a script run on an MLflow tracking server, and wires `examples/hf_ptq/hf_ptq.py` up to it via `--mlflow <tracking-uri>` so a PTQ run can be reproduced from its MLflow entry alone. Without the flag, behavior is unchanged — every hook is gated on it. The logger lives in the library rather than the example so other scripts can record runs the same way: it takes a tracking URI, an experiment name and an explicit `enabled` flag, with params, tags and artifacts passed in. `hf_ptq.py` supplies only the PTQ-specific pieces (its params, the resolved recipe, the quantization summaries). `mlflow` is an optional dependency, imported only once tracking is enabled, so it is not a new requirement for the library. The run is opened **before the model loads**, so a bad URI or an unreachable server fails in seconds rather than after hours of calibration. The invocation and the recipe are uploaded at that point too, which keeps a crashed run useful: it is still recorded, with status `FAILED` and its log attached. Uploaded artifacts: | Artifact | Contents | | --- | --- | | `command.txt` | The full invocation, copy-pasteable | | `version.txt` | The ModelOpt version that ran (also a searchable tag) | | `recipe/resolved_recipe.yaml` | The `--recipe` with `$import`s expanded | | `logs/hf_ptq.log` | Everything the run printed, including a crash traceback | | `summary/quant_summary.txt` | Per-quantizer summary (unless `--no-verbose`) | | `summary/moe.html` | Per-expert calibration token counts, when the run produces them | Plus model / format / calibration settings as searchable params, and `user` / `hostname` / `modelopt_version` / `git_sha` tags. Three design points worth review: 1. **The recipe is uploaded resolved, not verbatim.** A recipe may be a directory or use `$import`s, so the source file is not self-contained. For `huggingface/qwen3_6_moe/auto_quantize/w4a16_nvfp4_fp8_at_6p0bits-active_moe` the source is 2,230 B / 58 lines against 7,563 B / 308 lines resolved — the raw file records under 30% of what actually ran. 2. **`hf_ptq.py` has no logging framework** (bare `print()`), so the log is produced by teeing stdout/stderr. Handlers that libraries bound to `sys.stderr` at import time are re-pointed at the tee for the run's duration and handed back afterwards; without that, `transformers` / `huggingface_hub` warnings reach the console but never the log. Native (C-level) output is still not captured — documented in the README. 3. **The recipe upload lives in the caller, not the library.** That keeps `modelopt.recipe` out of `modelopt.torch.utils`, which would otherwise risk a `modelopt.torch.utils` → `modelopt.recipe` → `modelopt.torch.quantization` → `modelopt.torch.utils` import cycle. 4. **MLflow failures never fail the quantization.** Startup validation is fatal by design (it is before any GPU work); the end-of-run upload is best-effort. Only the main rank uploads, so `--use_fsdp2` runs produce a single run. ### Usage ```bash python hf_ptq.py \ --pyt_ckpt_path <huggingface_model_card> \ --recipe general/ptq/nvfp4_default-kv_fp8_cast \ --export_path <quantized_ckpt_path> \ --mlflow https://<your-mlflow-server>/ ``` ``` [mlflow] experiment: $USER/hf_ptq/<checkpoint basename>-<recipe name> [mlflow] run: https://<your-mlflow-server>/#/experiments/13/runs/c243352e... ``` `--mlflow_experiment` and `--mlflow_run_name` override the defaults (`$USER/hf_ptq/<basename>-<recipe name or --qformat>`, and the UTC start time). Passing `--mlflow` with no value uses `$MLFLOW_TRACKING_URI`. Authentication uses MLflow's own env vars. ### Testing **Unit** — 51 tests in `tests/unit/torch/utils/test_mlflow.py` for the library, plus 13 in `tests/examples/hf_ptq/test_hf_ptq_args.py` for the hf_ptq wiring. CPU-only, no network and no `mlflow` dependency (driven against a stub module). Covers experiment-name derivation and sanitization, URI accept/reject, tee pass-through, the pre-bound-handler redirect, artifact renaming, skipping absent optional outputs, the disabled path, and `version.txt`. 85 tests pass together with the existing `test_hf_ptq_args.py` / `test_example_utils.py`. **Hardware** — real PTQ runs against a live MLflow server: | Run | Result | | --- | --- | | Qwen3-0.6B, NVFP4 PTQ, 1×B200 | `FINISHED`, all artifacts, sane post-quant generations | | Qwen3.6-35B-A3B MoE, AutoQuantize `w4a16_nvfp4_fp8_at_6p0bits-active_moe`, 2×B200 | `FINISHED` in 63 min, search hit `effective bits: 6.00`; 106 KB log capturing every per-layer decision, 4.4 MB quant summary | | Qwen3.6-35B-A3B, plain NVFP4 PTQ, 2×B200 | `FINISHED` | | Qwen3-0.6B re-run after the library move, 1×H200 | `FINISHED`, all five artifacts including `version.txt` | | Run **without** `--mlflow` after the review fixes | exactly 1 `[load_recipe]` line and 0 `[mlflow]` lines, confirming the untracked path is untouched | | Two runs sharing one `--export_path`, second crashed early | second run uploads **no** summary — the first run's 124 KB file on disk is correctly not attributed to it, and its traceback is in the log | | Crash mid-run (gated HF dataset) | `FAILED` recorded with log + traceback attached, summaries correctly absent | | Malformed URI | Rejected by `argparse` with a `Did you mean https://…?` hint | | Unreachable host | Fails in 9.9 s total, before any model load | | No `--mlflow` | Exit 0, no MLflow output, unchanged export | **Coverage gap, stated plainly:** `summary/moe.html` is verified only against a synthetic file (unit test + a real upload). It could not be produced naturally — `expert_token_count` buffers live on `_QuantSparseSequentialMoe`, while Qwen3.5/3.6 experts take the fused `_QuantFusedExperts` path, so no such file is written for these models regardless of `--moe_calib_experts_ratio`. The uploader's conditional is correct; the branch simply had no natural input available here. ### Before your PR is "*Ready for review*" - Is this change backward compatible?: ✅ — new optional flags only; no `--mlflow` means no behavior change. - If you copied code from any other sources or added a new PIP dependency, did you follow guidance in `CONTRIBUTING.md`: ✅ — adds `mlflow` as an optional extra in `pyproject.toml` (`nvidia-modelopt[mlflow]`, folded into `all`) and to `examples/hf_ptq/requirements.txt`. Apache-2.0 (permissive). Imported lazily, so it is not required to install or import ModelOpt. No code copied from other sources. - Did you write any new necessary tests?: ✅ — 29 new unit tests. - Did you update [Changelog](https://github.com/NVIDIA/Model-Optimizer/blob/main/CHANGELOG.rst)?: ✅ — 0.47 New Features. - Did you get Claude approval on this PR?: ❌ — `/claude review` not yet run. A self-review was done first and its six findings are fixed in the third commit (the notable one: gathering the MLflow inputs re-read the recipe on *every* run, including without `--mlflow`). ### Additional Information The one deliberate coverage gap is `summary/moe.html`, described under Testing: no model available here takes the sparse-sequential MoE path that writes it, so it is covered by unit test and a synthetic upload rather than a natural one. The uploader treats it as an optional output and skips it when absent, which is exercised by test. 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Signed-off-by: Chenjie Luo <chenjiel@nvidia.com> Co-authored-by: Claude Opus 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
- [2026/06/26] 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 | Examples | Docs |
|---|---|---|---|
| Post Training Quantization | Compress model size by 2x-4x, speeding up inference while preserving model quality! | [HF LLMs / VLMs] [Megatron-Bridge LLMs / VLMs] [Diffusers] [ONNX] [Windows] | [docs] |
| Quantization Aware Training / Distillation | Refine accuracy of quantized models even further with a few training steps! | [Hugging Face] [Megatron-Bridge] | [docs] |
| Pruning | Reduce your model parameters or memory footprint and accelerate inference by removing unnecessary weights! | [General] [Megatron-Bridge] | |
| Distillation | Reduce deployment model size by teaching small models to behave like larger models! | [Hugging Face] [Megatron-Bridge] [Megatron-LM] | [docs] |
| Speculative Decoding | Train draft modules to predict extra tokens during inference! | [Hugging Face] [Megatron-LM] | [docs] |
| Sparsity | Efficiently compress your model by storing only its non-zero parameter values and their locations | [Hugging Face] | [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 / 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
For AI-assisted development setup, see the agent tooling notes.
Top Contributors
Happy optimizing!
