Abram, On Thu, Jun 28, 2012 at 6:11 PM, Abram Demski <[email protected]> wrote:
> > (Steve, can you give any reason to think otherwise? In what practical > situations does it help to have an analog computer?) > This is a very important - and difficult question to answer. It really has little to do with continuous vs. digital representation. Some venues, like unidirectional cause and effect relationships compute easily with present digital techniques. However, these are fairly rare and trivial in our complex world. Other venues, where there is no direction to the flow of "information", where things interact as relationships rather than as causers and effectors, either require a different approach, or require a LOT of back and forth unidirectional iteration to make work. Digital computers for the most part compute formulas, whereas analog computers for the most part solve differential equations. N-body problems work according to differential equations that define the interactions. Our world is "just" a GIGANTIC differential equation. For ~100 years an analog computer computed the world's tide tables. That gorgeous antique brass and steel computer is now in a glass case at NOAA headquarters. I once spent part of an afternoon understanding every sprocket on it. It "computed" with sprockets, bicycle chain, etc., simulating the gravitational effects of the moon, Jupiter, etc., as well as the inertia of the water in inlets. Eventually, the application was moved to a CDC 7600 mainframe because digital technology finally caught up. However, tides are basically a 2-D problem. Many transformer and other magnetics designers STILL use fish tanks full of salty water with conductive foil shapes in them to generate the 3-D fields needed to predict their operation. It is a LOT easier to simply move some foil around in a fish tank, than to wait hours for a "modern" PC to do the same digitally. Of course, these problems are trivial compared to what we do in our own minds. Our world works via countless bidirectional and multidirectional interactions, and these sorts of things just don't "compute" in any reasonable way with simplistic unidirectional function computing machines, like present-day digital computers. Another significant effect is the MUCH greater simplicity of interacting with analog systems. This is hard to explain to people who have never seen one in action. The only way I survived my differential equations class was to stop by the Aeronautics and Astronautics department and patch my homework problems into their EAI TR-20 analog computer. It took me about an hour to plot a week of homework problems. That was a LONG time ago (before the first integrated circuits), but even today this would be a challenge to do this in Mathematica as quickly and easily, because of the need to create and type complex instructions, rather than simply plugging wires into places according to the terms in an equation. "Modern" digital approaches are SO mired in the low-level detail of their implementations that it is really hard to imagine how they might do anything intelligent. However bidirectional analog approaches are at a MUCH higher level - enough higher that you can actually imagine how they might work to accomplish REALLY complex things. This is a bit like comparing assembly language with high level languages. It is hard to see how individual assembly coded instructions could all work together to do things that are really high level, but throw in high level languages and supporting libraries and it takes MUCH less imagination to see how they could work. I hope this answers your question. Steve ========================== > On Thu, Jun 28, 2012 at 7:05 AM, Peter Voss <[email protected]> wrote: > >> This issues has bothered me for a long time, and I’d like to explore it a >> bit:**** >> >> ** ** >> >> While digital computers obviously can be set up to solve equations, there >> still seems to be a significant difference in efficiency of simulating/ >> calculating versus physical analog ‘doing’/ execution – like for example in >> solving an n-body problem. Real systems system just produce the result by >> interaction of all the forces (electro/ mechanical), while computers have >> to approximate/ iterate. **** >> >> ** ** >> >> Key question: Are there AGI common problems where digital/simulated >> approaches need hyper-exponential amounts of computing power compared to >> physical systems? Is this kind of equation-solving core to AGI? I don’t >> think so, but…**** >> >> ** ** >> >> Other may be able to formulate this better. **** >> >> ** ** >> >> What has bothered me is the glib assertion that a digital computer an >> calculate to any arbitrary level of precision (true)… but does the cost >> become unworkable in practice, even with Moore’s law.**** >> >> ** ** >> >> Peter**** >> >> ** ** >> >> *From:* Steve Richfield [mailto:[email protected]] >> *Sent:* Thursday, June 28, 2012 6:39 AM >> *To:* AGI >> *Subject:* Re: [agi] Happy 100th Birthday Alan Turing - No, computers >> will never think, but machines will!**** >> >> ** ** >> >> Hey everyone, >> >> Remember my discussions about how computers fundamentally compute >> functions, while biological neurons appear to fundamentally solve equations >> - a MUCH higher level thing to do. It appears possible to design something >> resembling a computer to do this, but NOT to simulate this sort of >> functionality in any sort of practical way because of the astronomical >> inefficiency of solving huge systems of simultaneous NON-linear equations >> using conventional computational methods. >> >> No, I don't think that we need any sort of silicon wetware, but we DO >> appear to need a radically more advanced sort of "computer", but probably >> NOT anything that Turing has ever thought of - in short, NOT a "Turing >> machine". >> >> Besides, you'll never get 2-D silicon to work like 3-D wetware. >> >> Steve >> ================**** >> *AGI* | Archives <https://www.listbox.com/member/archive/303/=now> >> <https://www.listbox.com/member/archive/rss/303/7190161-766c6f07> | >> Modify <https://www.listbox.com/member/?&;> Your Subscription >> <http://www.listbox.com> >> > > > > -- > Abram Demski > http://lo-tho.blogspot.com/ > > *AGI* | Archives <https://www.listbox.com/member/archive/303/=now> > <https://www.listbox.com/member/archive/rss/303/10443978-6f4c28ac> | > Modify<https://www.listbox.com/member/?&;>Your Subscription > <http://www.listbox.com> > -- Full employment can be had with the stoke of a pen. 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