That's not even my second objection. My second objection is the rate of Entropy of the computer that would be using to make that computation, the amount of mass of the computer that would be required to use and how long it could continue to make computations before the heat death of computer. Also you would have to consider the fact that as performing multivariate calculus of the expanding universe that is completely gravitationally bound would require that the computer that is performing the calculations that govern the simulation to expand at a rate faster than the simulation that it is computing. Eventually what ever the rate of Entropy is in the Universe of the computer that would be simulating our Universe is would exceed the capability of it to exchange information from one end of the machine to the next as it eventually starts to expand faster than whatever the equivalent of the speed of light would be in the simulating universe.