Faiss.NET

C# bindings for Faiss.

• Faiss v1.14.1
• .NET 9.0

Warning

This library is under active construction and currently not usable yet.

Implemented Indexes

• IndexFlatIP
• IndexFlatL2
• IndexHNSW

Also, a generic Index factory is implemented which can be used to instantiate all other Faiss supported indexes.

This library aims to be as "bare metal" as possible while being straightforward to work with.

Additionally, Index serialization/deserialization and GPU Indexes + sharding is supported.

Supported Platforms:

Platform	x64	arm64
Windows	✅	✅
Linux	✅	✅
MacOS	✅	✅

GPU Acceleration:

Platform	x64	arm64
CUDA (Linux)	✅	✅
ROCm (Linux)	✅	❌

Installation

Prerequisites

Windows

You need a C++ redistributable installed. E.g.

$ winget install --id Microsoft.VCRedist.2015+.x64 --silent

Linux

OpenBLAS, OpenMP and Fortran runtimes must be installed. E.g.

$ sudo apt-get install -y libopenblas0 libgomp1 libgfortran5

MacOS

An OpenMP runtime is required. E.g.

$ brew install libomp

NuGet

Get the base NuGet:

$ dotnet add package Faiss.NET

Then pick a native package:

Either cpu only or with additional gpu support.

CPU only

$ dotnet add package Faiss.NET.Native

CPU+GPU

$ dotnet add package Faiss.NET.Gpu.Cuda # Linux only
$ dotnet add package Faiss.NET.Windows
$ dotnet add package Faiss.NET.MacOS

or

$ dotnet add package Faiss.NET.Native.Gpu.Rocm # Linux x64 only
$ dotnet add package Faiss.NET.Windows
$ dotnet add package Faiss.NET.MacOS

Usage

Basic

using Faiss.NET;

int dimensions = 4;
using var index = new FaissIndex<FaissIndexFlatL2>(new FaissIndexFlatL2(dimensions));

float[] vectors = { 1.0f, 2.0f, 3.0f, 4.0f };

index.Add(vectors);

using var searchResult = index.Search(vectors, 1);

float distance = searchResult.Distances[0]; // 0.0f
long label = searchResult.Labels[0]; // 0

Examples

Low-Level index usage

using Faiss.NET;

int dimensions = 2;
using var index = new FaissIndexFlatIP(dimensions);

float[] vectors = { 2.0f, 3.0f };
index.Add(1, vectors);

float[] distances = new float[1];
long[] labels = new long[1];

index.Search(1, vectors, 1, distances, labels);

long foundLabel = labels[0]; // 0
float foundDistance = distances[0]; // 13