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# FP-Quant

[FP-Quant](https://github.com/IST-DASLab/FP-Quant) is a family of quantization algorithms tailored for the Blackwell generation of Nvidia GPUs. The goal is to allow for efficient post-training quantization (PTQ) and quantization-aware training (QAT) of LLMs in the [MXFP4 and NVFP4 data-types](https://www.opencompute.org/documents/ocp-microscaling-formats-mx-v1-0-spec-final-pdf).

This integration accompanies the pre-print of the [**Bridging the Gap Between Promise and Performance for Microscaling FP4 Quantization**](https://arxiv.org/abs/2509.23202) pre-print.

Currently, only QAT is only supported with `pseudoquantization=True`. Models can either be quantized on the fly with `quantization_config=FPQuantConfig()`:

```python
from transformers import AutoModelForCausalLM, AutoTokenizer, FPQuantConfig
import torch

model = AutoModelForCausalLM.from_pretrained(
    "qwen/Qwen3-8B",
    quantization_config=FPQuantConfig(),
    device_map="auto",
    dtype=torch.bfloat16,
)
```

or pre-processed with GPTQ for better quality (see [FP Format Quantization Harness](https://github.com/IST-DASLab/FP-Quant)).

You can choose between MXFP4 and NVFP4 with `FPQuantConfig(forward_dtype="mxfp4")`. NVFP4 provides better quality but uses a little more memory.

A **Blackwell-generation GPU is required** to run the kernels. Runtime support for FP-Quant is implemented through the [QuTLASS](https://github.com/IST-DASLab/qutlass) library and a lightweight PyTorch interface lib [`fp_quant`](https://github.com/IST-DASLab/FP-Quant/tree/master/inference_lib). We recommend installing the former **from source** and the latter with  `pip install fp_quant`.

Users **without a Blackwell-generation GPU** , can use the method with `quantization_config=FPQuantConfig(pseudoquant=True)` without having to install [QuTLASS](https://github.com/IST-DASLab/qutlass). This would provide no speedups but would fully emulate the effect of quantization.

> [!TIP]
> Find models pre-quantized with FP-Quant in the official ISTA-DASLab [collection](https://huggingface.co/collections/ISTA-DASLab/fp-quant-6877c186103a21d3a02568ee).

## torch.compile

FP-Quant is fully compatible with [torch.compile](https://pytorch.org/tutorials/intermediate/torch_compile_tutorial.html).

```python
import torch
from transformers import AutoModelForCausalLM, AutoTokenizer, FPQuantConfig

model = AutoModelForCausalLM.from_pretrained(
    "qwen/Qwen3-8B",
    quantization_config=FPQuantConfig(),
    device_map="auto",
    dtype=torch.bfloat16,
)

model.forward = torch.compile(model.forward, mode="max-autotune", fullgraph=True)
```

## Speedups

FP-Quant currently performs best for very large batch size processing.

See [QuTLASS README](https://github.com/IST-DASLab/qutlass/blob/main/README.md) for speedups.
