I'm kind of scratching my head here, can someone explain what problem this solves? There's already a CLR and already a way to build native apps for Win 8, etc. This is a new CLR that can run new 'native' apps?
It gives faster startup time (due to AOT compilation rather than JIT), and doesn't require that the .NET framework be installed. Possibly better runtime performance, but I wouldn't expect huge gains there. P/Invoke should have lower overhead, which may be highly relevant for some things.
I suspect that there's things that require this which they haven't announced yet, since on its own it seems like something kinda nice but not beneficial enough to justify creating.
Yeah I don't understand the need to get rid of a .NET framework dependency though. This only supports building Windows store apps, which only run on devices that have the .NET framework right now...
One admittedly crazy theory is that this is laying the groundwork for building iOS apps and therefore would compete with Xamarin. Any kind of JIT would not be allowed on the iOS app store.
Start up times could be a big deal to compete with iOS? Especially in similar app lifecycle models where apps could be stopped and restarted implicitly by the OS?
"It [...] doesn't require that the .NET framework be installed."
Are you sure? You still need the standard libraries, a garbage collector, its security checks when loading other code, and may want to use its compiler from your code. Together, that's a lot, maybe all, of what's in the framework.
The standard library base is huge... they already split things into a desktop and full profile for the .Net installer. This will only need to include those portions of the library your app actually uses, which is generally a pretty small part (including GC). Not to mention future versions of the .Net runtime not needing to be installed on the target machine.
If I remember ngen is very architecture/platform specific - that is why it has to be done on the target machine. This sounds like it is done ahead of time with support for a variety of architectures.
It seems like this is basically just the same thing that Mono has done for a long time with AOT. I'm not really sure how it differs from the Ngen tool, though.
.NET Native addresses many of the same issues as Mono AOT but it has a radically different basis. We had the advantage of hindsight :)
The biggest difference with NGen is the fact that .NET Native doesn't ever "fall back" to JIT compiled code. There are other differences--refactored runtime, static-optimized libraries, static marshalling, etc.--which can be seen by the perf wins over NGen. We're seeing 40% startup performance gain over NGen apps for top Windows Store apps.
@apardoe, one question: where will the compilation to machine instruction happen? From some comments in this thread, it seems that it will happen at app store server and not at developer's box. If that is the case then why will I need anything to do any settings in VS for building projects?
@rajeevk, we could compile from MSIL and not tell the developer. But you probably appreciate the chance to test out the app on your own the way your user will run it. After all, you'll want to profile it or maybe find that last on-device, optimized-only bug...
Reflection.Emit isn't allowed in the Windows Store profile so we haven't handled it in this go-around. Expression compile is supported and handled properly.
