SOLVED: "That Alien Message" by Eliezer Yudkowsky (RIO)
Short story on the premise that this universe is simulated. Basically had the first contact with 'aliens' be stars that were blinking in code (iirc: 20 stars, widely separated across the night sky). But from our perspective they blinked very slowly (on/off once a year, or something similar), and they were stupid (because code runs much faster than meat). So when the blinks start happening, everyone starts analyzing them, and figuring things out - happens really quickly on our end (20-100 years? - but they're still working on their message), and then we have to wait around for them to finish "typing". (ie: brings to mind the cheela in Dragon's Egg). So, the bulk of humanity goes into cold storage (12?-16? billion?), and waits out the slow simulators, until we can do something about it. The simulators were using this universe as an AI to answer questions/solve problems.
Short story on the premise that this universe is simulated. Basically had the first contact with 'aliens' be stars that were blinking in code (iirc: 20 stars, widely separated across the night sky). But from our perspective they blinked very slowly (on/off once a year, or something similar), and they were stupid (because code runs much faster than meat). So when the blinks start happening, everyone starts analyzing them, and figuring things out - happens really quickly on our end (20-100 years? - but they're still working on their message), and then we have to wait around for them to finish "typing". (ie: brings to mind the cheela in Dragon's Egg). So, the bulk of humanity goes into cold storage (12?-16? billion?), and waits out the slow simulators, until we can do something about it. The simulators were using this universe as an AI to answer questions/solve problems.
Inspired by this request: universe created to generate new experiences
If anyone is interested in the philosophical background to the simulation argument: "Are You Living In a Computer Simulation?" by Nick Bostrom
Another anonymous story along the same lines.