On-device ML research with MLX and Swift

The Swift programming language has a lot of potential to be used for machine learning research because it combines the ease of use and high-level syntax of a language like Python with the speed of a compiled language like C++.

MLX is an array framework for machine learning research on Apple silicon. MLX is intended for research and not for production deployment of models in apps.

MLX Swift expands MLX to the Swift language, making experimentation on Apple silicon easier for ML researchers.

As part of this release we are including:

We are releasing all of the above under a permissive MIT license.

This is a big step to enable ML researchers to experiment using Swift.


MLX has several important features for machine learning research that few if any existing Swift libraries support. These include:

For more information on MLX see the documentation.

The Swift programming language is fast, easy-to-use, and works well on Apple silicon. With MLX Swift, you now have a researcher-friendly machine learning framework with the ability to easily experiment on different platforms and devices.

A Quick Tour

Getting set up with MLX Swift is quick and easy with Xcode or SwiftPM.

In MLX Swift, building and performing operations with N-dimensional arrays is simple. In the following example, all of the operations will be run on the default device, which is the GPU unless otherwise specified.

import MLX
import MLXRandom

let r = MLXRandom.normal([2])
// array([-0.125875, 0.264235], dtype=float32)

let a = MLXArray(0 ..< 6, [3, 2])
// array([[0, 1],
//        [2, 3],
//        [4, 5]], dtype=int32)

// last element of 0th row
print(a[0, -1])
// array(1, dtype=int32)

// slice of the first two rows        
print(a[0 ..< 2])
// array([[0, 1],
//        [2, 3]], dtype=int32)

// add with broadcast
let b = a + r

// array([[-0.510713, 1.04633],
//        [1.48929, 3.04633],
//        [3.48929, 5.04633]], dtype=float32)

You can also use function transformations in MLX Swift. Function transformations in MLX are useful for training models with automatic differentiation as well as optimizing compute graphs for speed or memory use. Below is an example which computes the gradient of a function.

func fn(_ x: MLXArray) -> MLXArray {

let gradFn = grad(fn)

let x = MLXArray(1.5)
let dfdx = gradFn(x)

// prints 2 * 1.5 = 3

The documentation contains a few more complete examples to help you get started with MLX Swift:

Further Resources

Here are a few more resources to get started with MLX Swift: