Furthermore, reality itself is the "simulation". It takes the entire universe at one time t1 as input, transforms it according to the functions known as the fun

Furthermore, reality itself is the "simulation". It takes the entire universe at one time t1 as input, transforms it according to the functions known as the fundamental forces, to produce the entire universe at time t2 as output, where t1 and t2 are one discrete time step apart. Restricting the "simulation" on a subset of the input is bound to introduce errors.