---
license: mit
task_categories:
- feature-extraction
- sentence-similarity
- text-retrieval
dataset_info:
  features:
  - name: text
    dtype: string
  - name: length_category
    dtype: string
  - name: source
    dtype: string
  splits:
  - name: train
    num_bytes: 373887763
    num_examples: 8000
  download_size: 210093799
  dataset_size: 373887763
configs:
- config_name: default
  data_files:
  - split: train
    path: data/train-*
tags:
- embedding
- benchmark
- long-context
- deepinfra
- rag
- wikitext
language:
- en

size_categories:
- 1K<n<10K
---


# Variable Length Embedding Benchmark (VLEB)

## Dataset Summary
**VLEB (Variable Length Embedding Benchmark)** is a specialized dataset designed to evaluate the performance, latency, and stability of **embedding models and rerankers** across a wide spectrum of context lengths. 

Unlike standard datasets that focus on short passages, VLEB provides a balanced distribution of text ranging from standard RAG chunks to maximum-context documents (up to 32k tokens). It is constructed from `wikitext-103-raw-v1` using a **smart-clipping strategy** that preserves semantic integrity without splitting words.

This benchmark is essential for:
- **Length Generalization:** Testing if models maintain semantic understanding as context grows.
- **RAG Profiling:** Measuring encoding latency and memory usage at different bins.
- **"Lost-in-the-Middle" Analysis:** Evaluating retrieval degradation in long-context windows.

## Data Structure

The dataset consists of **8,000 samples**, strictly balanced across 4 length categories (2,000 samples per bin). Token counts are calculated using the `Qwen/Qwen2.5-7B-Instruct` tokenizer.

| Category | Token Range (Qwen) | Typical Use Case |
| :--- | :--- | :--- |
| **Short** | 512 - 2,048 | Standard RAG chunks, abstracts, news snippets. |
| **Medium** | 2,048 - 8,192 | Full articles, technical reports, single-file code. |
| **Long** | 8,192 - 16,384 | Multiple papers, book chapters, long legal contracts. |
| **Very Long** | 16,384 - 32,000 | Entire books, massive documentation, stress testing context limits. |

## Usage

```python
from datasets import load_dataset

# Load the full dataset
dataset = load_dataset("ovuruska/variable-length-embedding-bench")

# Filter for specific length requirements
short_contexts = dataset.filter(lambda x: x['length_category'] == 'Short')
very_long_contexts = dataset.filter(lambda x: x['length_category'] == 'Very Long')

print(f"Sample Text ({very_long_contexts[0]['length_category']}):")
print(very_long_contexts[0]['text'][:200] + "...")

```

## Construction Methodology

1. **Source:** The dataset is derived from the `wikitext-103-raw-v1` corpus.
2. **Stream Buffering:** The raw text was processed as a continuous stream rather than isolated lines.
3. **Smart Clipping:** A buffer system accumulated tokens until a target length (randomly selected within bin ranges) was met. The text was then clipped at the exact token boundary and decoded back to string, ensuring **no words are split** and the text remains natural.
4. **Validation:** All samples were re-tokenized to ensure they strictly fall within their assigned bin limits.

## Citation

If you use this dataset for benchmarking, please cite:

```bibtex
@misc{vleb_2026,
  author = {DeepInfra Engineering Team},
  title = {Variable Length Embedding Benchmark (VLEB)},
  year = {2026},
  publisher = {Hugging Face},
  howpublished = {\url{[https://huggingface.co/datasets/DeepInfra/variable-length-embedding-benchmark](https://huggingface.co/datasets/DeepInfra/variable-length-embedding-benchmark)}}
}

```