Disco Go

🔥 Recommendations for Go using collaborative filtering

• Supports user-based and item-based recommendations
• Works with explicit and implicit feedback
• Uses high-performance matrix factorization

Installation

Run:

go get github.com/ankane/disco-go

Getting Started

Import the package

import "github.com/ankane/disco-go"

Prep your data in the format userId, itemId, value

data := disco.NewDataset[string, string]()
data.Push("user_a", "item_a", 5.0)
data.Push("user_a", "item_b", 3.5)
data.Push("user_b", "item_a", 4.0)

IDs can be integers or strings

data.Push(1, "item_a", 5.0)

If users rate items directly, this is known as explicit feedback. Fit the recommender with:

recommender, err := disco.FitExplicit(data)

If users don’t rate items directly (for instance, they’re purchasing items or reading posts), this is known as implicit feedback. Use 1.0 or a value like number of purchases or page views for the dataset, and fit the recommender with:

recommender, err := disco.FitImplicit(data)

Get user-based recommendations - “users like you also liked”

recommender.UserRecs(userId, 5)

Get item-based recommendations - “users who liked this item also liked”

recommender.ItemRecs(itemId, 5)

Get predicted ratings for a specific user and item

recommender.Predict(userId, itemId)

Get similar users

recommender.SimilarUsers(userId, 5)

Examples

MovieLens

Load the data

data, err := disco.LoadMovieLens()

Create a recommender

recommender, err := disco.FitExplicit(data, disco.Factors(20))

Get similar movies

recommender.ItemRecs("Star Wars (1977)")

Storing Recommendations

Save recommendations to your database.

Alternatively, you can store only the factors and use a library like pgvector-go. See an example.

Algorithms

Disco uses high-performance matrix factorization.

• For explicit feedback, it uses the stochastic gradient method with twin learners
• For implicit feedback, it uses the conjugate gradient method

Specify the number of factors and iterations

recommender, err := disco.FitExplicit(data, disco.Factors(8), disco.Iterations(20))

Progress

Pass a callback to show progress

callback := func(info disco.FitInfo) { fmt.Printf("%+v\n", info) }
recommender, err := disco.FitExplicit(data, disco.Callback(callback))

Note: TrainLoss and ValidLoss are not available for implicit feedback

Validation

Pass a validation set with explicit feedback

recommender, err := disco.FitEvalExplicit(trainSet, validSet)

The loss function is RMSE

Cold Start

Collaborative filtering suffers from the cold start problem. It’s unable to make good recommendations without data on a user or item, which is problematic for new users and items.

recommender.UserRecs(newUserId, 5) // returns empty array

There are a number of ways to deal with this, but here are some common ones:

• For user-based recommendations, show new users the most popular items
• For item-based recommendations, make content-based recommendations

Reference

Get ids

recommender.UserIds()
recommender.ItemIds()

Get the global mean

recommender.GlobalMean()

Get factors

recommender.UserFactors(userId)
recommender.ItemFactors(itemId)

References

• A Learning-rate Schedule for Stochastic Gradient Methods to Matrix Factorization
• Faster Implicit Matrix Factorization

History

View the changelog

Contributing

Everyone is encouraged to help improve this project. Here are a few ways you can help:

• Report bugs
• Fix bugs and submit pull requests
• Write, clarify, or fix documentation
• Suggest or add new features

To get started with development:

git clone https://github.com/ankane/disco-go.git
cd disco-go
go mod tidy
go test -v