nativeAOT/CoreRT output?

Martin · December 20, 2020, 2:23pm

As several commercial monogames (Carrion and SoR4) have already used AOT, I thought I would try AOT compiling following this tutorial:

github.com

dotnet/corert/blob/master/samples/MonoGame/README.md

# Building a MonoGame app with CoreRT

CoreRT is an AOT-optimized .NET Core runtime. This document will guide you through compiling a .NET Core [MonoGame](http://www.monogame.net) game with CoreRT.

_Please ensure that [pre-requisites](../prerequisites.md) are installed._

## Create .NET Core MonoGame project
Open a new shell/command prompt window and run the following commands.
```bash
> dotnet new --install MonoGame.Template.CSharp
> dotnet new mgdesktopgl -o MyGame
> cd MyGame
```

This will install .NET Core MonoGame template and create empty game project. .NET Core MonoGame port lives at https://github.com/cra0zy/MonoGame/tree/core currently. Thank you @cra0zy for the great work! 

Verify that the empty game builds and runs. You should see blue window:

```bash
> dotnet run

This file has been truncated. show original

I successfully compiled the blank project for both non-AOT and AOT (which outputs the blue screen), however, I ran into problems with the NeonShooter/Platformer2D samples.

The language of the tutorial isn’t very clear where it says you need to “transplant links to sample sources and assets”, I interpreted this to mean to overwrite the references to the Content/Game in ‘.csproj’ and ‘Program.cs’, respectively. This compiled with no errors, and the non-AOT version of the game worked (screenshot 1), however, the AOT version crashed (screenshot 2). I tried debugging the AOT version, and the error seems to originate from loading the Content (screenshot 3).

Can someone ( @harry-cpp ) offer some advice on how to do AOT properly? AOT support is a pretty big deal, especially the imminent wasm output, which is expected to bring monogame to a far larger audience than ever before. Thus, incorporating a workable AOT guide into the official documentation would seem like it would help many developers.

PS: I am on VS2019 16.9.0 preview 2.0, Windows 10 and Monogame 3.8.

Martin · March 10, 2021, 11:23pm

I managed to make this work. Here are my steps and a github of a minimal working example for the NeonShooter sample.

STEPS:
1. Add the Nuget package ‘Microsoft.DotNet.ILCompiler’ into your VS2019 preview project
2. Create and reference the rd.xml file
3. run x64 Native Tools Command Prompt for VS 2019 via: dotnet publish -r win-x64 -c release

TROUBLESHOOTING:
1. NU1101 Unable to find package nuget error.
The official tutorial advocated adding the nuget source into the project file, but for some reason that did not work for me. Instead I added the experimental Nuget source for VS (Tools > Nuget Package Manager > Package Manager Settings) with settings:

dotnet-experimental
https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-experimental/nuget/v3/index.json

2. Some of the Nuget Packages don’t work. The one I used was 6.0.0-preview.3.21153.3 which did.

3. You get the error “fatal error LNK1112: module machine type ‘x86’ conflicts with target machine type ‘x64’”.
You run dotnet publish in the Developer Powershell / Command prompt, which are x86. You must start up an external x64 Native Tools Command Prompt.

4. You get "EXEC : error : Failed to load assembly ‘Microsoft.Xna.Framework.Content.ContentTypeReader’"
Delete this from the csproj file:

  <ItemGroup>
    <TrimmerRootAssembly Include="Microsoft.Xna.Framework.Content.ContentTypeReader" Visible="false" />
  </ItemGroup>

5. Compiles but will produce runtime crash on
"Font = content.Load<SpriteFont>("Font");"
You forgot to add the rd.xml file to your project with the appropriate contents:

<Directives>
    <Application>
        <Assembly Name="MonoGame.Framework">
            <Type Name="Microsoft.Xna.Framework.Content.ListReader`1[[System.Char,mscorlib]]" Dynamic="Required All" />
        </Assembly>
        <Assembly Name="mscorlib" />
    </Application>
</Directives>

6. Runtime crash referencing the Content.
You tried to launch the compiled .exe under the subfolder \native. The one that will work is under \publish.

7. Here is a minimal example for the Neonshooter sample game that should just compile.

KakCAT · March 11, 2021, 9:03am

Have you tested how much faster is the AOT version compared to the default version?

I’m assuming it’s obviously faster, but wondering how much.

Martin · March 20, 2021, 10:06pm

For GPU bound games like the Neonshooter, I don’t think there would be any benefit.
For CPU bound games, think strategy games with 000s of units, or generating worlds via Perlin noise etc, there I would expect to be some improvement depending on how you do it. However, I haven’t fully tested AOT for performance yet. I may post some more results if/when I have the time. In anycase, I am pleased to say that as far as compatibility goes, pretty much everything works so far, including multiplayer, threading and Myra UI.

Karob · September 8, 2021, 2:24pm

For number 5, I also had to add the following to my .csproj

  <ItemGroup>
    <RdXmlFile Include="rd.xml" />
  </ItemGroup>