C-Pack: Packed Resources For General Chinese Embeddings
Written for the Research library (claude-opus-5-5) from the paper text, in our own words: the license "arXiv — non-exclusive licence to distribute" does not allow redistributing the text itself. Original — arxiv.org/pdf/2309.07597
Summary
Chinese has lagged behind English in general-purpose text embeddings because it lacks large public training sets, competitive models and a broad evaluation suite. C-Pack fills this gap with a bundle of resources. C-MTEB is a Chinese extension of MTEB with a unified evaluation protocol and pipeline. C-MTP is a training corpus of text pairs. Most of it is mined from web sources such as Baike, Zhihu and news sites by exploiting structural links (title–document, question–answer and similar), and it is then cleaned and supplemented with labeled data. BGE is a family of encoders trained in three stages:
- embedding-oriented pre-training,
- weakly supervised contrastive learning with very large batches of in-batch negatives,
- instruction-based fine-tuning on labeled pairs.
When released, BGE beat earlier Chinese embedding models on C-MTEB by over 10%. An English counterpart reached state of the art on MTEB. The open data, models and recipe have become a widely used foundation for Chinese retrieval and RAG systems.
Key points
- C-MTEB: 35 public datasets across 6 task types (retrieval, STS, pair classification, classification, reranking, clustering).
- C-MTP: about 100M Chinese text pairs, plus a separately released English set of about 200M pairs. The authors describe both as the largest public embedding training sets.
- BGE sizes: small (24M), base (102M) and large (326M) parameters. English BGE (large) averages 64.23 on MTEB.
- Ablations:
- Fine-tuning on C-MTP (labeled) raises the C-MTEB average from 59.0 (BGE-pretrain) to 63.96.
- Scaling the batch size up to 19,200 consistently helps, especially retrieval.
- Instructions and the custom pre-trained encoder each add further gains.
- Adoption: over 20M HuggingFace downloads by April 2024, with integration into Langchain and LLamaIndex.
Cited by
- LLM2Vec: Large Language Models Are Secretly Powerful Text Encoders
- A Survey on Hallucination in Large Language Models: Principles, Taxonomy, Challenges, and Open Questions
- LongLLMLingua: Accelerating and Enhancing LLMs in Long Context Scenarios via Prompt Compression
- Context Volume Drives Performance: Tackling Domain Shift in Extremely Low-Resource Translation via RAG
- Improving Text Embeddings with Large Language Models
- Multilingual E5 Text Embeddings: A Technical Report
- Smarter, Better, Faster, Longer: A Modern Bidirectional Encoder for Fast, Memory Efficient, and Long Context Finetuning and Inference
- mGTE: Generalized Long-Context Text Representation and Reranking Models for Multilingual Text Retrieval
- Qwen3 Embedding: Advancing Text Embedding and Reranking Through Foundation Models
Cite
@misc{xiao2023c,
title = {{C-Pack: Packed Resources For General Chinese Embeddings}},
author = {Xiao, Shitao and Liu, Zheng and Zhang, Peitian and Muennighoff, Niklas and Lian, Defu and Nie, Jian-Yun},
year = {2023},
doi = {10.48550/arxiv.2309.07597},
eprint = {2309.07597},
archivePrefix = {arXiv},
url = {https://doi.org/10.48550/arxiv.2309.07597}
}References
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