Lightweight Nearest Neighbors with Flexible Backends

Quickstart • Main Features • Supported Backends • Installation

Vicinity is a light-weight, low-dependency vector store. It provides a simple and intuitive interface for nearest neighbor search, with support for different backends and evaluation.

There are many nearest neighbors packages and methods out there. However, we found it difficult to compare them. Every package has its own interface, quirks, and limitations, and learning a new package can be time-consuming. In addition to that, how do you effectively evaluate different packages? How do you know which one is the best for your use case?

This is where Vicinity comes in. Instead of learning a new interface for each new package or backend, Vicinity provides a unified interface for all backends. This allows you to easily experiment with different indexing methods and distance metrics and choose the best one for your use case. Vicinity also provides a simple way to evaluate the performance of different backends, allowing you to measure the queries per second and recall.

Quickstart

Install the package with:

pip install vicinity

Optionally, install any of the supported backends, or simply install all of them with:

pip install vicinity[all]

The following code snippet demonstrates how to use Vicinity for nearest neighbor search:

import numpy as np
from vicinity import Vicinity, Backend, Metric

# Create some dummy data
items = ["triforce", "master sword", "hylian shield", "boomerang", "hookshot"]
vectors = np.random.rand(len(items), 128)

# Initialize the Vicinity instance (using the basic backend and cosine metric)
vicinity = Vicinity.from_vectors_and_items(
    vectors=vectors,
    items=items,
    backend_type=Backend.BASIC,
    metric=Metric.COSINE
)

# Create a query vector
query_vector = np.random.rand(128)

# Query for nearest neighbors with a top-k search
results = vicinity.query(query_vector, k=3)

# Query for nearest neighbors with a threshold search
results = vicinity.query_threshold(query_vector, threshold=0.9)

# Query with a list of query vectors
query_vectors = np.random.rand(5, 128)
results = vicinity.query(query_vectors, k=3)

Saving and loading a vector store:

vicinity.save('my_vector_store')
vicinity = Vicinity.load('my_vector_store')

Evaluating a backend:

# Use the first 1000 vectors as query vectors
query_vectors = vectors[:1000]

# Evaluate the Vicinity instance by measuring the queries per second and recall
qps, recall = vicinity.evaluate(
    full_vectors=vectors,
    query_vectors=query_vectors,
)

Main Features

Vicinity provides the following features:

• Lightweight: Minimal dependencies and fast performance.
• Flexible Backend Support: Use different backends for vector storage and search.
• Serialization: Save and load vector stores for persistence.
• Evaluation: Easily evaluate the performance of different backends.
• Easy to Use: Simple and intuitive API.

Supported Backends

The following backends are supported:

• BASIC: A simple (exact matching) flat index for vector storage and search.
• HNSW: Hierarchical Navigable Small World Graph (HNSW) for ANN search using hnswlib.
• USEARCH: ANN search using Usearch. This uses a highly optimized version of the HNSW algorithm.
• ANNOY: "Approximate Nearest Neighbors Oh Yeah" for approximate nearest neighbor search.
• PYNNDESCENT: ANN search using PyNNDescent.
• FAISS: All FAISS indexes are supported:
  • flat: Exact search.
  • ivf: Inverted file search.
  • hnsw: Hierarchical Navigable Small World Graph.
  • lsh: Locality Sensitive Hashing.
  • scalar: Scalar quantizer.
  • pq: Product Quantizer.
  • ivf_scalar: Inverted file search with scalar quantizer.
  • ivfpq: Inverted file search with product quantizer.
  • ivfpqr: Inverted file search with product quantizer and refinement.
• VOYAGER: Voyager is a library for performing fast approximate nearest-neighbor searches on an in-memory collection of vectors.

NOTE: the ANN backends do not support dynamic deletion. To delete items, you need to recreate the index. Insertion is supported in the following backends: FAISS, HNSW, and Usearch. The BASIC backend supports both insertion and deletion.

Backend Parameters

Backend	Parameter	Description	Default Value
BASIC	metric	Similarity metric to use (cosine, euclidean).	"cosine"
ANNOY	metric	Similarity metric to use (dot, euclidean, cosine).	"cosine"
	trees	Number of trees to use for indexing.	100
	length	Optional length of the dataset.	None
FAISS	metric	Similarity metric to use (cosine, l2).	"cosine"
	index_type	Type of FAISS index (flat, ivf, hnsw, lsh, scalar, pq, ivf_scalar, ivfpq, ivfpqr).	"hnsw"
	nlist	Number of cells for IVF indexes.	100
	m	Number of subquantizers for PQ and HNSW indexes.	8
	nbits	Number of bits for LSH and PQ indexes.	8
	refine_nbits	Number of bits for the refinement stage in IVFPQR indexes.	8
HNSW	metric	Similarity space to use (cosine, l2).	"cosine"
	ef_construction	Size of the dynamic list during index construction.	200
	m	Number of connections per layer.	16
PYNNDESCENT	metric	Similarity metric to use (cosine, euclidean, manhattan).	"cosine"
	n_neighbors	Number of neighbors to use for search.	15
USEARCH	metric	Similarity metric to use (cos, ip, l2sq, hamming, tanimoto).	"cos"
	connectivity	Number of connections per node in the graph.	16
	expansion_add	Number of candidates considered during graph construction.	128
	expansion_search	Number of candidates considered during search.	64
VOYAGER	metric	Similarity space to use (cosine, l2).	"cosine"
	ef_construction	The number of vectors that this index searches through when inserting a new vector into the index.	200
	m	The number of connections between nodes in the tree’s internal data structure.	16

Installation

The following installation options are available:

# Install the base package
pip install vicinity

# Install all backends
pip install vicinity[all]

# Install specific backends
pip install vicinity[annoy]
pip install vicinity[faiss]
pip install vicinity[hnsw]
pip install vicinity[pynndescent]
pip install vicinity[usearch]
pip install vicinity[voyager]

License

MIT