Sometimes I still marvel about how in most time-travel stories nobody thinks of this.
The alternate way of computing this is to not actually discard the future, but to split it off to a separate timeline
Or maybe also another one, somewhat related to the main post—let the universe compute, in it’s own meta-time, a fixed point [0] of reality (that is, the whole of time between the start and the destination of time travel gets recomputed into a form that allowed it to be internally consistent) and continue from there. You could imagine the universe computer simulating casually the same period of time again and again until a fixed point is reached, just like the iterative algorithms used to find it for functions.
Or maybe also another one, somewhat related to the main post—let the universe compute, in it’s own meta-time, a fixed point [0] of reality (that is, the whole of time between the start and the destination of time travel gets recomputed into a form that allowed it to be internally consistent) and continue from there. You could imagine the universe computer simulating casually the same period of time again and again until a fixed point is reached, just like the iterative algorithms used to find it for functions.
[0] - http://en.wikipedia.org/wiki/Fixed_point_(mathematics)