Annoy-go

A go binding of Spotify's Annoy (Approximate Nearest Neighbors Oh Yeah). Codes are generated using Swig from the lastest(by now) Annoy commit(2be37c9e015544be2cf60c431f0cccc076151a2d).

Build

CGO is required to build this project. Use the following command to add it to your go.mod:

go get github.com/oligo/annoy-go@latest

API Usage

Swig does not generates document for the go source. Please consult the documents of Spotify Annoy for API usage. Here is a simple example located in the example directory to demostrate the basic usage.

package main

import (
	"errors"
	"fmt"
	"os"

	annoyindex "github.com/oligo/annoy-go"
)

const indexFile = "./embeddings.ann"

func main() {
	embeddings := [][]float32{
		{0.1, 0.2, 0.31},
		{0.4, 0.55, 0.67},
	}

	index := annoyindex.NewAnnoyIndexAngular(len(embeddings[0]))
	if PathExists(indexFile) {
		if ret := index.Load(indexFile, false); !ret {
			panic("Failed to load file without prefault")
		}
	} else {
		defer func() {
			index.Build(5)
			index.Save(indexFile, false)
		}()
		for i, embedding := range embeddings {
			index.AddItem(i, embedding)
		}
	}

	distance1 := index.GetDistance(0, 1)
	distance2 := index.GetDistance(0, 2)
	fmt.Printf("distance between 1 and 2: %f, 0 and 3: %f\n", distance1, distance2)

	// query with a vector
	query := []float32{0.12, 0.22, 0.3}
	result := []int{}
	distances := []float32{}
	index.GetNnsByVector(query, 10, -1, &result, &distances)

	for i, idx := range result {
		vector := []float32{}
		index.GetItem(idx, &vector)
		fmt.Printf("found vector: %v, distance: %f\n", result, distances[i])
	}
}

func PathExists(path string) bool {
	stat, err := os.Stat(path)
	if errors.Is(err, os.ErrNotExist) {
		return false
	}

	if err == nil || stat != nil {
		return true
	}

	return false
}