FAISS — Facebook 的高效密集向量相似度搜索和聚类库

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Faiss

Facebook’s library for efficient similarity search and clustering of dense vectors. Supports billions of vectors, GPU acceleration, and various index types (Flat, IVF, HNSW). Use for fast k-NN search, large-scale vector retrieval, or when you need pure similarity search without metadata. Best for high-performance applications.

技能元数据

来源	可选 — 通过 hermes skills install official/mlops/faiss
路径	optional-skills/mlops/faiss
版本	1.0.0
作者	Orchestra Research
许可证	MIT
依赖项	faiss-cpu, faiss-gpu, numpy
平台	linux, macos
标签	RAG, FAISS, Similarity Search, Vector Search, Facebook AI, GPU Acceleration, Billion-Scale, K-NN, HNSW, High Performance, Large Scale

参考：完整 SKILL.md

:::info 以下是 Hermes 在触发此技能时加载的完整技能定义。这是技能激活时代理所看到的指令。 :::

FAISS - Efficient Similarity Search

Facebook AI’s library for billion-scale vector similarity search.

何时使用 FAISS

Use FAISS when:

• Need fast similarity search on large vector datasets (millions/billions)
• GPU acceleration required
• Pure vector similarity (no metadata filtering needed)
• High throughput, low latency critical
• Offline/batch processing of embeddings

数据指标：

• 31,700+ GitHub stars
• Meta/Facebook AI Research
• Handles billions of vectors
• C++ with Python bindings

Use alternatives instead:

• Chroma/Pinecone: Need metadata filtering
• Weaviate: Need full database features
• Annoy: Simpler, fewer features

快速开始

安装

# CPU only
pip install faiss-cpu
 
# GPU support
pip install faiss-gpu

基本使用

import faiss
import numpy as np
 
# Create sample data (1000 vectors, 128 dimensions)
d = 128
nb = 1000
vectors = np.random.random((nb, d)).astype('float32')
 
# Create index
index = faiss.IndexFlatL2(d)  # L2 distance
index.add(vectors)             # Add vectors
 
# Search
k = 5  # Find 5 nearest neighbors
query = np.random.random((1, d)).astype('float32')
distances, indices = index.search(query, k)
 
print(f"Nearest neighbors: {indices}")
print(f"Distances: {distances}")

Index types

1. Flat (exact search)

# L2 (Euclidean) distance
index = faiss.IndexFlatL2(d)
 
# Inner product (cosine similarity if normalized)
index = faiss.IndexFlatIP(d)
 
# Slowest, most accurate

2. IVF (inverted file) - Fast approximate

# Create quantizer
quantizer = faiss.IndexFlatL2(d)
 
# IVF index with 100 clusters
nlist = 100
index = faiss.IndexIVFFlat(quantizer, d, nlist)
 
# Train on data
index.train(vectors)
 
# Add vectors
index.add(vectors)
 
# Search (nprobe = clusters to search)
index.nprobe = 10
distances, indices = index.search(query, k)

3. HNSW (Hierarchical NSW) - Best quality/speed

# HNSW index
M = 32  # Number of connections per layer
index = faiss.IndexHNSWFlat(d, M)
 
# No training needed
index.add(vectors)
 
# Search
distances, indices = index.search(query, k)

4. Product Quantization - Memory efficient

# PQ reduces memory by 16-32×
m = 8   # Number of subquantizers
nbits = 8
index = faiss.IndexPQ(d, m, nbits)
 
# Train and add
index.train(vectors)
index.add(vectors)

Save and load

# Save index
faiss.write_index(index, "large.index")
 
# Load index
index = faiss.read_index("large.index")
 
# Continue using
distances, indices = index.search(query, k)

GPU 加速

# Single GPU
res = faiss.StandardGpuResources()
index_cpu = faiss.IndexFlatL2(d)
index_gpu = faiss.index_cpu_to_gpu(res, 0, index_cpu)  # GPU 0
 
# Multi-GPU
index_gpu = faiss.index_cpu_to_all_gpus(index_cpu)
 
# 10-100× faster than CPU

LangChain integration

from langchain_community.vectorstores import FAISS
from langchain_openai import OpenAIEmbeddings
 
# Create FAISS vector store
vectorstore = FAISS.from_documents(docs, OpenAIEmbeddings())
 
# Save
vectorstore.save_local("faiss_index")
 
# Load
vectorstore = FAISS.load_local(
    "faiss_index",
    OpenAIEmbeddings(),
    allow_dangerous_deserialization=True
)
 
# Search
results = vectorstore.similarity_search("query", k=5)

LlamaIndex integration

from llama_index.vector_stores.faiss import FaissVectorStore
import faiss
 
# Create FAISS index
d = 1536
faiss_index = faiss.IndexFlatL2(d)
 
vector_store = FaissVectorStore(faiss_index=faiss_index)

最佳实践

1. Choose right index type - Flat for <10K, IVF for 10K-1M, HNSW for quality
2. Normalize for cosine - Use IndexFlatIP with normalized vectors
3. Use GPU for large datasets - 10-100× faster
4. Save trained indices - Training is expensive
5. Tune nprobe/ef_search - Balance speed/accuracy
6. Monitor memory - PQ for large datasets
7. Batch queries - Better GPU utilization

性能

索引类型	构建时间	搜索时间	内存	准确率
Flat	Fast	Slow	High	100%
IVF	Medium	Fast	Medium	95-99%
HNSW	Slow	Fastest	High	99%
PQ	Medium	Fast	Low	90-95%

资源

• GitHub： https://github.com/facebookresearch/faiss ⭐ 31,700+
• Wiki: https://github.com/facebookresearch/faiss/wiki
• 许可证： MIT