An unambiguous recipe cannot exist since it would have to give precise answers to ambiguous questions such as: if there are two identical simulations of you running on two computers, should they be counted as two copies or one?
Well this is your utility function, so you tell me! Imagine a hacker is able to get into the simulations and replace pleasant experiences by horrible torture. Does your utility function care twice as much if he hacks both simulations versus hacking just one of them? (My guess is that it does).
It wouldn’t be exactly twice but you’re more or less right. However, it has no direct relation to probability. To see this, imagine you’re a paperclip maximizer. In this case you don’t care about torture or anything of the sort: you only care about paperclips. So your utility function specifies a way of counting paperclips but no way of counting copies of you.
From another angle, imagine your two simulations are offered a bet. How should they count themselves? Obviously it depends on the rules of the bet: whether the payoff is handed out once or twice. Therefore, the counting is ambiguous.
What you’re trying to do is writing the utility function as a convex linear combination of utility functions associated with different copies of you. Once you accomplish that, the coefficients of the combination can be interpreted as probabilities. However, there is no such canonical decomposition.
It wouldn’t be exactly twice but you’re more or less right. However, it has no direct relation to probability. To see this, imagine you’re a paperclip maximizer. In this case you don’t care about torture or anything of the sort: you only care about paperclips. So your utility function specifies a way of counting paperclips but no way of counting copies of you.
From another angle, imagine your two simulations are offered a bet. How should they count themselves? Obviously it depends on the rules of the bet: whether the payoff is handed out once or twice. Therefore, the counting is ambiguous.
What you’re trying to do is writing the utility function as a convex linear combination of utility functions associated with different copies of you. Once you accomplish that, the coefficients of the combination can be interpreted as probabilities. However, there is no such canonical decomposition.