Google finalizes Android P as Android 9 “Pie,” launching today (ars technica)

> Based on the app usage patterns, each app is placed in one of five priority buckets. The system limits the device resources available to each app based on which bucket the app is in.
> [...]
> The system dynamically assigns each app to a priority bucket, and reassigns the apps as needed. The system may rely on a preloaded app that uses machine learning to determine how likely each app is to be used, and assigns apps to the appropriate buckets. If the system app is not present on a device, the system defaults to sorting apps based on how recently they were used.

I guess that preloaded app is part of the proprietary Google services, so non-Googlified AOSP devices can either use the default recently-used behaviour or implement their own equivalent app. (I'm not certain but I don't see why else they'd design it as an optional app.)

https://deepmind.com/blog/deepmind-meet-android/ gives a tiny bit more detail on the algorithm:

> we’ve partnered with the Android team to develop a feature called Adaptive Battery that uses a deep convolutional neural net to predict which apps you’ll use in the next few hours and which you probably won’t use until later.