faiss相似性搜索和向量聚类库 faiss: A library for efficient similarity search and clustering of dense vectors.

Faiss是一个有效的相似性搜索和密集向量聚类的库。它包含搜索任意大小的向量集的算法，包括不适合放入RAM的数据集。它还包含用于评估和参数调整的支持代码。Faiss是用C ++编写的，包含Python / numpy的完整包装。一些最有用的算法是在GPU上实现的。它由 Facebook AI Research开发。

Faiss

Faiss is a library for efficient similarity search and clustering of dense vectors. It contains algorithms that search in sets of vectors of any size, up to ones that possibly do not fit in RAM. It also contains supporting code for evaluation and parameter tuning. Faiss is written in C++ with complete wrappers for Python/numpy. Some of the most useful algorithms are implemented on the GPU. It is developed by Facebook AI Research.

NEWS

NEW: version 1.4.0 (2018-08-30) no more crashes in pure Python code

NEW: version 1.3.0 (2018-07-12) support for binary indexes

NEW: latest commit (2018-02-22) supports on-disk storage of inverted indexes, see demos/demo_ondisk_ivf.py

NEW: latest commit (2018-01-09) includes an implementation of the HNSW indexing method, see benchs/bench_hnsw.py

NEW: there is now a Facebook public discussion group for Faiss users at https://www.facebook.com/groups/faissusers/

NEW: on 2017-07-30, the license on Faiss was relaxed to BSD from CC-BY-NC. Read LICENSE for details.

Introduction

Faiss contains several methods for similarity search. It assumes that the instances are represented as vectors and are identified by an integer, and that the vectors can be compared with L2 distances or dot products. Vectors that are similar to a query vector are those that have the lowest L2 distance or the highest dot product with the query vector. It also supports cosine similarity, since this is a dot product on normalized vectors.

Most of the methods, like those based on binary vectors and compact quantization codes, solely use a compressed representation of the vectors and do not require to keep the original vectors. This generally comes at the cost of a less precise search but these methods can scale to billions of vectors in main memory on a single server.

The GPU implementation can accept input from either CPU or GPU memory. On a server with GPUs, the GPU indexes can be used a drop-in replacement for the CPU indexes (e.g., replace IndexFlatL2with GpuIndexFlatL2) and copies to/from GPU memory are handled automatically. Results will be faster however if both input and output remain resident on the GPU. Both single and multi-GPU usage is supported.

Building

The library is mostly implemented in C++, with optional GPU support provided via CUDA, and an optional Python interface. The CPU version requires a BLAS library. It compiles with a Makefile and can be packaged in a docker image. See INSTALL.mdfor details.

How Faiss works

Faiss is built around an index type that stores a set of vectors, and provides a function to search in them with L2 and/or dot product vector comparison. Some index types are simple baselines, such as exact search. Most of the available indexing structures correspond to various trade-offs with respect to

• search time
• search quality
• memory used per index vector
• training time
• need for external data for unsupervised training

The optional GPU implementation provides what is likely (as of March 2017) the fastest exact and approximate (compressed-domain) nearest neighbor search implementation for high-dimensional vectors, fastest Lloyd's k-means, and fastest small k-selection algorithm known. The implementation is detailed here.

Full documentation of Faiss

The following are entry points for documentation:

• the full documentation, including a tutorial, a FAQand a troubleshooting sectioncan be found on the wiki page
• the doxygen documentationgives per-class information
• to reproduce results from our research papers, Polysemous codesand Billion-scale similarity search with GPUs, refer to the benchmarks README.

Authors

The main authors of Faiss are:

• Hervé Jégouinitiated the Faiss project and wrote its first implementation
• Matthijs Douzeimplemented most of the CPU Faiss
• Jeff Johnsonimplemented all of the GPU Faiss
• Lucas Hosseiniimplemented the binary indexes

Reference

Reference to cite when you use Faiss in a research paper:

    @article{JDH17,
  title={Billion-scale similarity search with GPUs},
  author={Johnson, Jeff and Douze, Matthijs and J{\'e}gou, Herv{\'e}},
  journal={arXiv preprint arXiv:1702.08734},
  year={2017}
}

Join the Faiss community

For public discussion of Faiss or for questions, there is a Facebook public discussion group at https://www.facebook.com/groups/faissusers/

We monitor the issues pageof the repository. You can report bugs, ask questions, etc.

License

Faiss is BSD-licensed. We also provide an additional patent grant.