4 ms·

It depends on which aspects you're trying to simulate accurately. If you consider the physically optimal implementation of any function (e.g. the optimal NAND g

It depends on which aspects you're trying to simulate accurately. If you consider the physically optimal implementation of any function (e.g. the optimal NAND gate), that system cannot be simulated in real time: the simulation will always be slower, pretty much by definition. Insofar that physics optimally implements itself, you cannot simulate reality in general without a massive performance hit (think about the recursive absurdity of the simulator simulating itself). What you can try to do is simulate the most salient/important aspects of reality, but the more physically optimal these aspects become, the harder simulation of them will get. For instance, as our computers become faster and more efficient, fast simulation of our reality becomes progressively harder. That's without even considering the physical optimality of natural systems, of course, which I imagine is rather high.

naasking 2y ago
Simulated time does not need to match real time.
- breuleux 2y ago
  Depends on the application. If you're playing a video game, you want real time. If you're trying to predict something, the simulation needs to run faster than real time. If you're trying to model a new technology or a recurrent situation, up to a few orders of magnitude of slowdown is quite acceptable.
  - mr_toad 2y ago
    > Depends on the application. If you're playing a video game, you want real time. If the player is part of the simulation they won’t know.
    - breuleux 2y ago
      I mean, sure, but the value proposition of a slow simulation containing slow minds is a little dubious, isn't it? It would be neither cheap nor useful, so why would it be made?
      - naasking 2y ago
        There's considerable value actually. You could simulate a whole economy and test economic theories if you could simulate a country full of minds, all with different interests and values. There's no need for this kind of simulation to be real-time. That there's value in simulating lots of minds is the core premise of the simulation hypothesis.
        breuleux 2y ago
        We can't simply assert that this is valuable, we have to analyze it properly. Mass simulation will happen if the expected value of the simulation exceeds the opportunity cost of, well, everything else we could do with these resources instead. First, the expected value... it is, frankly, questionable. Certainly it's great in the best case scenario where we stumble upon a good system and then put it in application, but how likely is that? I can see several cases where the entire value would be sunk: * You will need to run not just one, but many simulations. However, the same argument that implies the simulation will be slower than reality also implies that it will be bigger than reality. The problem isn't merely that this simulation won't occur in real time, it's also that it's going to be physically enormous. Even running a single one would be quite the undertaking. * It is quite possible that an economic system would work very well at first, only to collapse 50 years later for a variety of difficult-to-foresee reasons. If the simulation runs too slowly, we may have to commit to a system before the simulation can demonstrate its collapse. Or wait centuries, but then the initial conditions may have diverged far too much for the experiment to translate. * We're not even guaranteed to glean any important insights from such a simulation. Civilization is a chaotic system that involves a ton of smart agents who constantly come up with paradigm-shifting inventions or new ways to bend and manipulate the system. It won't take much time before all you're doing is explore some random alternate future, although it's slower than real time, so it's actually some random alternate past. It's not useless, but it's middling. * And then you have to implement changes. Very sensitive to the current conditions, which change faster than the simulator can keep up with. Good luck. As for the second part of the equation, the opportunity cost: likely humongous. Insofar that simulation hardware is a general purpose substrate, there is a mind-boggling number of uses for it. If you can simulate minds faster than real time, sure, that's useful. If not, it's unclear to me how a poor imitation of a real thing would even crack the top 10 of things you'd want to do with this hardware. Sorry for all the text. I think the whole debate can be summarized like this: the simulation hypothesis makes sense if simulation is cheap, it falls apart if it isn't. And I don't think simulation is going to be cheap (unless it's quite crude and approximate, in which case it won't tell us much about reality.)

naasking 2y ago

Simulated time does not need to match real time.

breuleux 2y ago
Depends on the application. If you're playing a video game, you want real time. If you're trying to predict something, the simulation needs to run faster than real time. If you're trying to model a new technology or a recurrent situation, up to a few orders of magnitude of slowdown is quite acceptable.
- mr_toad 2y ago
  > Depends on the application. If you're playing a video game, you want real time. If the player is part of the simulation they won’t know.
  - breuleux 2y ago
    I mean, sure, but the value proposition of a slow simulation containing slow minds is a little dubious, isn't it? It would be neither cheap nor useful, so why would it be made?
    - naasking 2y ago
      There's considerable value actually. You could simulate a whole economy and test economic theories if you could simulate a country full of minds, all with different interests and values. There's no need for this kind of simulation to be real-time. That there's value in simulating lots of minds is the core premise of the simulation hypothesis.
      - breuleux 2y ago
        We can't simply assert that this is valuable, we have to analyze it properly. Mass simulation will happen if the expected value of the simulation exceeds the opportunity cost of, well, everything else we could do with these resources instead. First, the expected value... it is, frankly, questionable. Certainly it's great in the best case scenario where we stumble upon a good system and then put it in application, but how likely is that? I can see several cases where the entire value would be sunk: * You will need to run not just one, but many simulations. However, the same argument that implies the simulation will be slower than reality also implies that it will be bigger than reality. The problem isn't merely that this simulation won't occur in real time, it's also that it's going to be physically enormous. Even running a single one would be quite the undertaking. * It is quite possible that an economic system would work very well at first, only to collapse 50 years later for a variety of difficult-to-foresee reasons. If the simulation runs too slowly, we may have to commit to a system before the simulation can demonstrate its collapse. Or wait centuries, but then the initial conditions may have diverged far too much for the experiment to translate. * We're not even guaranteed to glean any important insights from such a simulation. Civilization is a chaotic system that involves a ton of smart agents who constantly come up with paradigm-shifting inventions or new ways to bend and manipulate the system. It won't take much time before all you're doing is explore some random alternate future, although it's slower than real time, so it's actually some random alternate past. It's not useless, but it's middling. * And then you have to implement changes. Very sensitive to the current conditions, which change faster than the simulator can keep up with. Good luck. As for the second part of the equation, the opportunity cost: likely humongous. Insofar that simulation hardware is a general purpose substrate, there is a mind-boggling number of uses for it. If you can simulate minds faster than real time, sure, that's useful. If not, it's unclear to me how a poor imitation of a real thing would even crack the top 10 of things you'd want to do with this hardware. Sorry for all the text. I think the whole debate can be summarized like this: the simulation hypothesis makes sense if simulation is cheap, it falls apart if it isn't. And I don't think simulation is going to be cheap (unless it's quite crude and approximate, in which case it won't tell us much about reality.)