At this point you are not talking about a simulation of a person, but rather a simulation of the entire world. Confronted with the knowledge that a GLUT exists predicting I will do anything, I will resolve to pick some relatively trivial decision each day, write down 10 choices, numbered 0 to 9, and then choose the item based on the first numerical digit I see written out on the 11th page of the first section of the New York Times for that day, excluding page numbers or references to page numbers. At that point, the simulation of me has to simulate the production of the next day's New York Times, which is tantamount to having to simulate the entire world.

Not that that is necessarily any harder to do than a complete and accurate simulation of an individual person, mind you.