ML. NET Release Process

This document describes the different kinds of ML. NET releases, how those releases are versioned, and how they are built.

Types of releases

ML. NET NuGets (of which there are approximately 25) are versioned with the following format: A.B.C<-D>, where A, B, and C are integers, and D is an optional string.

A - version number: If A is 0, this NuGet is considered a work in progress (WIP), and could be deleted at any time. If A is greater than 0, then we plan to support the corresponding NuGet indefinitely.
B - sub-version number: This number is consistent within each GA release and within each WIP release. Therefore, all GA NuGets that are released at the same time will have the same sub-version number, and all WIP releases that are released at the same time will have the same sub-version number, but a WIP release and a GA release that are released at the same time may have different sub-version numbers.
C - patch index: C starts at 0 and is incremented every time we introduce a bug fix between releases.
D - preview suffix: D is an optional suffix which contains the word "preview" followed by an integer or by a datetime string and an integer. If D is not included and A is not 0, then the API surface is locked and will not change in future releases.

ML. NET has four kinds of releases: daily builds, previews, periodic general availability (GA), and fix. We detail each kind of release below.

Daily builds: these can be downloaded from this NuGet feed, and are built automatically each time a commit is made to the main branch.
Preview: These releases are built from the corresponding A.B-preview-X GitHub branch, and are expected to meet a higher quality bar than the daily builds. These can also be downloaded from this NuGet feed, or within Visual Studio, as detailed below. When we introduce new API's in a preview release, we avoid doing a GA release at the same time (unless there are patches required for the last GA release). If there are no new API's, then we go straight to a GA release and skip the preview release.
GA: These releases are built from the corresponding A.B GitHub branch. They are rigorously tested, stable, and meant for general use. They are also the default choice when installing ML. NET via the Install-Package Microsoft.ML command, and are published to nuget.org
Fix: These releases include patches for bugs in either the preview or GA releases.

Versioning for releases

The table below explains how each of the elements in our versioning schema would change, relative to the previous release, for each kind of release.

Release type	Change in `A`	Change in `B`	Change in `C`	Change in `D`
Daily build	No change	No change	No change	A date-like stamp is added, i.e. `Microsoft.Extensions.ML 1.5.0-preview-28327-2`
Preview	No change	No change	No change	`preview` tag added to the most recent GA release, if this is the first preview, or preview index is incremented (i.e. `A.B.C-preview` -> `A.B.C-preview2`)
GA	Incremented for major releases, only for non-WIP NuGets. WIP NuGets maintain an `A` value of `0`	Incremented, or reset to 0 if `A` was incremented	Reset to 0	`preview` tag is removed
Fix	No change	No change	Incremented	No change

Note: to install the preview packages via the NuGet Package Manager in Visual Studio, you must make sure to check the "Include prerelease" checkbox: