X-Message-Number: 8191 Date: Wed, 7 May 1997 09:12:03 -0700 From: "Joseph J. Strout" <> Subject: Re: subsimulations I haven't taken part in this discussion for quite a while; I try not to jump in unless I have something to contribute (and time to contribute it!). Hopefully this message meets that standard... In Message #8185, Robert writes: >c) If people in the real world are motivated to simulate a world full of >people, the simulated people will also be so motivated, generating an >exploding set of subsimulations, effectively causing the original computer, >in the real world, to stop. I don't see how this could be. A simulation of a thing always runs slower than the "real" thing, unless the simulation is significantly simpler than the device running it. So my 180 MHz Macintosh can emulate a Commodore 64 in real time; it can also emulate a Pentium running Windows -- but substantially slower than a real Pentium. Within SoftWindows, I may perhaps be able to install a Mac emulator, and it will run slower than a Mac emulator running on a real Pentium, and MUCH slower than the real Mac. But suppose my Mac were fully multi-threaded (or instead of a real Mac, make the outermost Mac itself a simulation running on a Unix workstation). Another thread is simultaneously running which is, oh, finding prime numbers; and this other process has at least as high a priority as the simulation process. As we run simulations within simulations within simulations, does my prime-number search slow down? Not a bit. The simulations just get slower and slower, *with respect to my time scale* as an outside observer. Or, equivalently, with respect to the time scale of the outermost device. But with respect to the time scale of the next-to-last device (in this example, of SoftWindows), the simulation it's running hasn't slowed down a bit either. If it updated one simulation tick per 20 ticks of its own clock, then it's still doing so; it can have no "awareness" that its own clock is slowed down relative to the one above it. If we leave the realm of practicality and talk about planet-sized computers simulating billions of people, the same principles will hold. Maybe we're a simulation within a simulation within a simulation. Now we build a computer the size of Mars and start a simulation inside it. It will run along just swimmingly as far as we can tell. If the beings inside do the same thing, THEIR simulation will look slow to us, but just fine to them. And never mind that one second of our own time takes a million years for the ultimate creator, no matter what we're doing. So no matter how far you nest, things won't grind to a halt. As we peer deeper into layer after layer of simultation, it looks slower to us, but always fairly zippy to the simulators just above. And no amount of this will cause any slowing of the top-level simulation, which after all is just simulating atom movements and basic forces, and couldn't care less whether those atoms are arranged into clouds or computers. Regards, -- Joe ,------------------------------------------------------------------. | Joseph J. Strout Department of Neuroscience, UCSD | | http://www-acs.ucsd.edu/~jstrout/ | `------------------------------------------------------------------' Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=8191