gpt-oss-20B-NVFP4A16-BF16

GPT-OSS-20B-NVFP4

Model Overview

• Model Architecture: openai/gpt-oss-20b (Mixture of Experts, 128K context)
• Parameters: 20 billion (quantized from original MXFP4 to NVFP4)
• Input: Text
• Output: Text
• Model Optimizations:
  • Weight quantization: NVFP4 (4-bit floating point with E4M3 FP8 scaling)
  • Activation quantization: FP16 (W4A16 configuration)
  • Block size: 16 values per scaling factor
• Release Date: 8/30/2025
• Version: 1.0
• Model Developers: 2imi9

This model is a quantized version of OpenAI's GPT-OSS-20B using NVIDIA's advanced NVFP4 format. It follows the official NVIDIA TensorRT Model Optimizer methodology, providing superior accuracy retention compared to MXFP4 quantization while maintaining significant memory efficiency gains.

Key Features

• Advanced Quantization: Uses NVFP4 format with FP8 E4M3 scaling for enhanced precision
• Memory Efficient: ~75% size reduction from original model
• High Accuracy: 2-3% better validation loss compared to MXFP4 quantization
• Production Ready: Full vLLM support as of v0.13.0

Deployment

Use with vLLM (Recommended)

vLLM v0.13.0+ now includes native NVFP4 support via the EPLB (Expert-Parallel Load Balancing) system.

from vllm import LLM, SamplingParams
from transformers import AutoTokenizer

model_id = "2imi9/gpt-oss-20b-NVFP4"

# Initialize model and tokenizer
tokenizer = AutoTokenizer.from_pretrained(model_id, trust_remote_code=True)
llm = LLM(
    model=model_id, 
    tensor_parallel_size=1, 
    trust_remote_code=True,
    quantization="nvfp4"  # Enable NVFP4 quantization
)

# Configure sampling
sampling_params = SamplingParams(
    temperature=0.7,
    top_p=0.9,
    max_tokens=512
)

# Chat template example
messages = [
    {"role": "system", "content": "You are a helpful AI assistant."},
    {"role": "user", "content": "Explain quantum computing in simple terms."}
]

prompt = tokenizer.apply_chat_template(messages, tokenize=False, add_generation_prompt=True)
outputs = llm.generate([prompt], sampling_params)

print(outputs[0].outputs[0].text)

Multi-GPU Deployment

from vllm import LLM, SamplingParams

model_id = "2imi9/gpt-oss-20b-NVFP4"

# Multi-GPU with tensor parallelism
llm = LLM(
    model=model_id,
    tensor_parallel_size=2,  # Use 2 GPUs
    trust_remote_code=True,
    quantization="nvfp4",
    max_model_len=32768  # Adjust based on available VRAM
)

sampling_params = SamplingParams(
    temperature=0.7,
    top_p=0.9,
    max_tokens=1024
)

outputs = llm.generate(["Your prompt here"], sampling_params)

OpenAI-Compatible Server

# Start vLLM server with NVFP4 model
python -m vllm.entrypoints.openai.api_server \
    --model 2imi9/gpt-oss-20b-NVFP4 \
    --quantization nvfp4 \
    --tensor-parallel-size 1 \
    --max-model-len 32768 \
    --trust-remote-code \
    --host 0.0.0.0 \
    --port 8000

# Client usage
from openai import OpenAI

client = OpenAI(base_url="http://localhost:8000/v1", api_key="dummy")

response = client.chat.completions.create(
    model="2imi9/gpt-oss-20b-NVFP4",
    messages=[
        {"role": "system", "content": "You are a helpful assistant."},
        {"role": "user", "content": "Explain quantum computing in simple terms."}
    ],
    temperature=0.7,
    max_tokens=512
)

print(response.choices[0].message.content)

Use with Transformers (Fallback)

from transformers import AutoModelForCausalLM, AutoTokenizer
import torch

model_id = "2imi9/gpt-oss-20b-NVFP4"

# Load model and tokenizer
model = AutoModelForCausalLM.from_pretrained(
    model_id, 
    torch_dtype=torch.bfloat16,
    trust_remote_code=True,
    device_map="auto"
)
tokenizer = AutoTokenizer.from_pretrained(model_id, trust_remote_code=True)

# Generate text
prompt = "The future of artificial intelligence will"
inputs = tokenizer(prompt, return_tensors="pt").to(model.device)
outputs = model.generate(**inputs, max_new_tokens=200, temperature=0.7)
print(tokenizer.decode(outputs[0], skip_special_tokens=True))

Creation Process

This model was created using the official NVIDIA methodology with TensorRT Model Optimizer:

import torch
from transformers import AutoModelForCausalLM, AutoTokenizer
import modelopt.torch.quantization as mtq

# Load base model (upcast from original MXFP4 to BF16)
MODEL_ID = "openai/gpt-oss-20b"
model = AutoModelForCausalLM.from_pretrained(
    MODEL_ID, 
    torch_dtype=torch.bfloat16, 
    trust_remote_code=True, 
    device_map="auto"
)
tokenizer = AutoTokenizer.from_pretrained(MODEL_ID, trust_remote_code=True)

# Configure NVFP4 quantization
config = mtq.NVFP4_DEFAULT_CFG

# Calibration for optimal quantization
def forward_loop(model):
    calibration_prompts = [
        "The future of artificial intelligence is",
        "Machine learning has transformed",
        "Deep learning models are capable of"
    ]
    model.eval()
    with torch.no_grad():
        for prompt in calibration_prompts:
            inputs = tokenizer(
                prompt, 
                return_tensors="pt", 
                max_length=512, 
                truncation=True
            ).to(model.device)
            model(**inputs)

# Apply quantization
model = mtq.quantize(model, config, forward_loop)

# Save quantized model
model.save_pretrained("/path/to/output", safe_serialization=True)
tokenizer.save_pretrained("/path/to/output")

Performance Analysis

Quantization Quality

vLLM v0.13.0 NVFP4 Features

The latest vLLM release includes comprehensive NVFP4 support:

• EPLB Integration: NVFP4 support via Expert-Parallel Load Balancing (#29804)
• Blackwell Ultra Support: SM103 (GB300) native acceleration with CUDA 13 (#30484)
• DeepSeek Optimizations: Sparse prefill kernel for FP8 KV-cache compatibility (#27532)
• MLA FP8 Optimization: Enhanced performance with ReduceScatterSum (#29795)

NVFP4 Technical Advantages

Based on NVIDIA research findings:

• Enhanced Precision: E4M3 FP8 scaling factors reduce quantization errors
• Better Convergence: Improved training stability and accuracy recovery
• Blackwell Optimization: Native hardware acceleration on latest NVIDIA GPUs
• Training Efficiency: Purpose-built for both training and inference workflows

Recommended QAT Workflow

For production use requiring maximum accuracy, NVIDIA recommends:

1. Supervised Fine-Tuning (SFT) on task-specific data using BF16 precision
2. Quantization-Aware Training (QAT) to adapt weights to NVFP4 format
3. Validation against benchmarks and custom tasks

This approach can achieve up to 98% task-specific performance recovery.

Hardware Requirements

Optimal Performance (Native NVFP4 Acceleration)

Compatible Hardware (Software Emulation)

Framework Support Status

Model Format Details

This model contains the full BF16 weights along with quantization parameters that enable inference engines like vLLM and TensorRT-LLM to convert weights to true 4-bit NVFP4 format during model loading. The memory savings and performance benefits are realized at inference time, not during storage.

Use Cases

Ideal Applications

• Production Inference: Memory-constrained environments requiring high accuracy
• High-Throughput Serving: vLLM deployment with OpenAI-compatible API
• Research: NVFP4 quantization effectiveness studies
• Comparison Studies: Benchmarking against MXFP4 and other quantization methods
• Edge Deployment: High-performance models on resource-limited hardware

Performance Expectations

Limitations and Considerations

• Storage Size: Model stored in fake-quantized BF16 format (~39GB) for broad compatibility
• Runtime Conversion: True 4-bit compression achieved during inference engine loading
• Hardware Dependency: Optimal performance requires NVIDIA Blackwell architecture
• vLLM Version: Requires vLLM v0.13.0 or later for native NVFP4 support

Evaluation and Benchmarking

This model maintains the capabilities of the original GPT-OSS-20B while providing memory efficiency benefits. For comprehensive evaluation, test against:

• Language Modeling: Perplexity on standard datasets
• Downstream Tasks: Task-specific accuracy measurements
• Generation Quality: Human evaluation of output coherence
• Memory Usage: Deployment memory requirements vs. accuracy trade-offs

License

This model inherits the Apache 2.0 license from the base openai/gpt-oss-20b model. Commercial use is permitted under the same terms.

Citation

@misc{gpt-oss-20b-nvfp4-2025,
  title={GPT-OSS-20B-NVFP4: NVIDIA NVFP4 Quantized Large Language Model},
  author={2imi9},
  year={2025},
  url={https://huggingface.co/2imi9/gpt-oss-20b-NVFP4}
}

Acknowledgments

• Base Model: OpenAI team for GPT-OSS-20B architecture and training
• Quantization Framework: NVIDIA TensorRT Model Optimizer team
• NVFP4 Format: NVIDIA research team for advanced 4-bit floating point format
• Inference Engine: vLLM team for NVFP4 integration in v0.13.0
• Community: Hugging Face for model hosting and transformers library support