---
license: apache-2.0
base_model: answerdotai/ModernBERT-large
tags:
- onnx
- sequence-classification
- text-classification
- query-classifier
- modernbert
- llm-routing
pipeline_tag: text-classification
library_name: onnxruntime
---

# Query Classifier ONNX (ModernBERT-large Fine-Tuned)

A CPU-optimized ONNX sequence classification model fine-tuned from **ModernBERT-large** to classify user queries into **`low`**, **`medium`**, and **`hard`** complexity levels. It is designed for LLM routing, enabling applications to dispatch simple requests to smaller, lower-cost models while reserving larger reasoning models for complex, multi-step tasks.

---

## 📌 Model Details

- **Base Architecture**: [`answerdotai/ModernBERT-large`](https://huggingface.co/answerdotai/ModernBERT-large) (`ModernBertForSequenceClassification`)
- **Training Data**: Fine-tuned on a manually curated dataset of **1,800 user queries** spanning factual QA, programming, reasoning, mathematics, and technical problem solving.
- **Model Format**: Int8 quantized ONNX (`model.onnx`, ~397 MB).
- **Inference Runtime**: Pure **ONNX Runtime + Hugging Face Rust `tokenizers`** — zero PyTorch or `transformers` runtime dependencies are required for inference.

---

## 🏷️ Class Labels & Definitions

| Class ID | Label | Description & Examples |
| :--- | :--- | :--- |
| **0** | **`low`** | Simple factual questions, basic definitions, direct short lookup, unit conversions.<br>*Example:* "What is the capital of France?", "How many days in a leap year?" |
| **1** | **`medium`** | Explanations, code snippets, summarizing text, multi-step instructions.<br>*Example:* "Explain how key-value storage works in Redis", "Write a python script to parse CSV files." |
| **2** | **`hard`** | Complex algorithms, multi-file code synthesis, lock-free concurrency, advanced mathematics.<br>*Example:* "Implement a lock-free SPMC queue in C++ using atomics", "Calculate the integral of x^2 * sin(x) dx." |

---

## 📊 Benchmark & Evaluation Results

Evaluated on an independent **held-out test set of 301 unseen queries** (balanced across `low`, `medium`, and `hard` buckets):

### Accuracy & F1 Breakdown

- **Overall Accuracy**: **88.04%**
- **Macro F1-Score**: **0.8797**

| Class | Precision | Recall | F1-Score | Support |
| :--- | :--- | :--- | :--- | :--- |
| **`low`** | **100.00%** | 81.00% | **0.8950** | 100 |
| **`medium`** | **82.18%** | 83.00% | **0.8259** | 100 |
| **`hard`** | **84.87%** | **100.00%** | **0.9182** | 101 |
| **Overall** | **88.04% Acc** | — | **0.8797 Macro-F1** | **301 total** |

### 🎯 Confusion Matrix (Actual vs. Predicted)

| Actual \ Predicted | `low` | `medium` | `hard` |
| :--- | :--- | :--- | :--- |
| **`low`** | **81** | 18 | 1 |
| **`medium`** | **0** | **83** | 17 |
| **`hard`** | **0** | **0** | **101** |

### Latency & Throughput Profile (CPU Execution)

| Metric | Measurement |
| :--- | :--- |
| **Median Latency (p50)** | **67.68 ms** |
| **Mean Latency** | **81.44 ms** |
| **p90 Latency** | **134.69 ms** |
| **p99 Latency** | **161.74 ms** |
| **Throughput** | **12.3 queries/sec** |

### 🧪 Reproducing Evaluation & Running Local Tests

The held-out test dataset and evaluation script are provided directly in the repository [`tests/`](tests) folder:
- [`tests/test_dataset.csv`](tests/test_dataset.csv): 301 held-out test queries (100 `low`, 100 `medium`, 101 `hard`).
- [`tests/evaluate.py`](tests/evaluate.py): Standalone evaluation script for computing accuracy, F1, confusion matrix, and latency profile.

To run the benchmark suite locally:
```bash
python tests/evaluate.py
```

---

## 🚀 Quickstart: Pure ONNX Runtime Usage

The model can be used directly with ONNX Runtime without requiring PyTorch or Transformers for inference.

### 1. Installation

```bash
pip install onnxruntime tokenizers numpy huggingface-hub
```

### 2. Python Code Example

```python
import numpy as np
import onnxruntime as ort
from tokenizers import Tokenizer
from huggingface_hub import hf_hub_download

# Repository details
REPO_ID = "prvn-ramesh/query-classifier-onnx"

# 1. Download model artifacts from Hugging Face Hub
model_path = hf_hub_download(repo_id=REPO_ID, filename="model.onnx")
tok_path = hf_hub_download(repo_id=REPO_ID, filename="tokenizer.json")

# 2. Load tokenizer and initialize ONNX Runtime session
tokenizer = Tokenizer.from_file(tok_path)
session = ort.InferenceSession(model_path, providers=["CPUExecutionProvider"])
label_map = {0: "low", 1: "medium", 2: "hard"}

def classify_query(text: str):
    # Tokenize input string
    encoded = tokenizer.encode(text)
    input_ids = np.array([encoded.ids], dtype=np.int64)
    attention_mask = np.array([encoded.attention_mask], dtype=np.int64)

    # Run inference session
    outputs = session.run(None, {
        "input_ids": input_ids,
        "attention_mask": attention_mask
    })
    
    # Softmax over logits
    logits = outputs[0][0]
    exp_logits = np.exp(logits - np.max(logits))
    probs = exp_logits / np.sum(exp_logits)
    
    pred_idx = int(np.argmax(probs))
    
    return {
        "label": label_map[pred_idx],
        "confidence": float(probs[pred_idx]),
        "scores": {label_map[i]: float(probs[i]) for i in range(len(probs))}
    }

# Example usage
query = "Write a lock-free multi-threaded SPMC queue in C++ using atomics"
result = classify_query(query)

print(f"Query: {query}")
print(f"Predicted Class: {result['label'].upper()} (Confidence: {result['confidence']:.2%})")
print(f"All Scores: {result['scores']}")
```

---

## 🙌 Citation & Acknowledgements

- Base model: [ModernBERT](https://huggingface.co/answerdotai/ModernBERT-large) developed by **Answer.AI** and **LightOn**.
- Frameworks: [ONNX Runtime](https://onnxruntime.ai/) and [Hugging Face Tokenizers](https://github.com/huggingface/tokenizers).