Programming language: Python
License: MIT License
Latest version: v0.5.0

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Status Documentation

Fast Python Collaborative Filtering for Implicit Datasets.

This project provides fast Python implementations of several different popular recommendation algorithms for implicit feedback datasets:

All models have multi-threaded training routines, using Cython and OpenMP to fit the models in parallel among all available CPU cores. In addition, the ALS and BPR models both have custom CUDA kernels - enabling fitting on compatible GPU's. Approximate nearest neighbours libraries such as Annoy, NMSLIB and Faiss can also be used by Implicit to speed up making recommendations.


Implicit can be installed from pypi with:

pip install implicit

Installing with pip will use prebuilt binary wheels on x86_64 Linux, Windows and OSX. These wheels include GPU support on Linux.

Implicit can also be installed with conda:

# CPU only package
conda install -c conda-forge implicit

# CPU+GPU package
conda install -c conda-forge implicit implicit-proc=*=gpu

Basic Usage

import implicit

# initialize a model
model = implicit.als.AlternatingLeastSquares(factors=50)

# train the model on a sparse matrix of user/item/confidence weights

# recommend items for a user
recommendations = model.recommend(userid, user_item_data[userid])

# find related items
related = model.similar_items(itemid)

The examples folder has a program showing how to use this to compute similar artists on the last.fm dataset.

For more information see the documentation.

Articles about Implicit

These blog posts describe the algorithms that power this library:

There are also several other blog posts about using Implicit to build recommendation systems:


This library requires SciPy version 0.16 or later and Python version 3.6 or later.

GPU Support requires at least version 11 of the NVidia CUDA Toolkit.

This library has been tested with Python 3.6, 3.7, 3.8, 3.9 and 3.10 on Ubuntu, OSX and Windows.


Simple benchmarks comparing the ALS fitting time versus Spark can be found here.

Optimal Configuration

I'd recommend configuring SciPy to use Intel's MKL matrix libraries. One easy way of doing this is by installing the Anaconda Python distribution.

For systems using OpenBLAS, I highly recommend setting 'export OPENBLAS_NUM_THREADS=1'. This disables its internal multithreading ability, which leads to substantial speedups for this package. Likewise for Intel MKL, setting 'export MKL_NUM_THREADS=1' should also be set.

Released under the MIT License

*Note that all licence references and agreements mentioned in the implicit README section above are relevant to that project's source code only.