First I've heard of analog computers but it sounds super interesting. So basically the structure of the system defined the algorithm and is therefore very specialized and efficient?
Analog Computers
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Re: Analog Computers
#32Earlier quoted context omitted.
Not really. FPGAs are fundamentally digital and pretty much give you a bunch of logic gates to work with ("Field-Programmable Gate Array"). The author's proposed architecture would instead provide an array of components that perform analog operations, such as summing, multiplication, and integration or differentiation, over analog voltages.
FPGAs are fundamentally analog, depending on if 'fundamental' means what was in the designer's head or what you actually fabricated. You are thinking about them and using them as if they were digital. Adrian Thompson at Sussex University used a genetic algorithm to auto-design FPGA circuits in the early 90s. Since no one told the GA that FPGAs were supposed to be logic circuits, it happily used the FPGA as an analog…
Obviously. But good luck implementing a human-comprehensible analog differential equation solver on one, without the help of a genetic algorithm, that doesn't depend (as Adrian Thompson's circuit did) on the temperature, the quirks of that specific board, and the effect of components which aren't even physically wired to it.
The difference isn't that FPGAs don't operate on analog voltages deep down (who said they don't?). The difference is in the set of tools and tolerances they give you, and in that sense FPGAs are only an analog coprocessor in the sense that a car can, technically, be used as a sailboat.
Re: Analog Computers
#33A good summary of analog computers can be found on the wikipedia article: https://en.wikipedia.org/wiki/Analog_computer Takeaway: Analog computers are limited in precision and by "analog noise"; the precision of the components used determine the precision of the output. Usually no more than 3 or 4 decimal places are possible, at least with the tech that was used in their heydey. I would say that is still close to the…
> Usually no more than 3 or 4 decimal places are possible By that do you mean accurate to 1 part in 100 (3dp) or 1000 (4dp) or what? Since the scale of a representation is arbitrary, I'm not sure what dp means here.
Good question. I guess precision is finally going to be fractions of the max voltage swing allowed by the computer. For example, if voltage goes from -5 to +5 volts, the voltage swing is 10v, and if noise allows 0.1mV of precision, then the precision is 1/100000 of the full voltage swing.
This could be expressed, at the end, simply in decibels, though. Signal-to-noise, as in classic analog systems.
Re: Analog Computers
#34Something that might be interesting is some kind of analog fpga for neural networks. Seems like NN weighting would translate well.
Re: Analog Computers
#35>The human brain is a great example – its processing power is estimated at about 38 petaflops, about two-fifths of that of TaihuLight.
Huh? So we now have computers more powerful than the human brain? I thought that was still some decades off. And how would one even measure such a thing? In the apples-to-apples comparison, a stupid human trick floating-point calculation savant might manage 1 flop/s.
Re: Analog Computers
#36So, Keith Emerson's Moog Synthesizer[0] was an analog computer, yes? [0] http://i.telegraph.co.uk/multimedia/archive/03593/emerson6_3...
Certainly. Most modular synths have all the basics - Sum, divide, multiply, add, XOR, etc.
And don’t forget, analogue random is the shit. In your face entropy!
Re: Analog Computers
#37Re: Analog Computers
#38Analog computing makes a lot of sense in the context of genetic algorithms and "deep learning" and I wouldn't be surprised if there's already some ASICs under design using those principles. One big challenge is that the design kits from the foundries aren't likely to include all the analog computer cells that would be needed (but perhaps for example a current mirror into a MIM capacitor could make for an integrator?)…
Genetic algos are inherently discrete, so I can't see analog computing being all that useful for them.
Re: Analog Computers
#39Earlier quoted context omitted.
What you're describing is generally accepted to be physically unrealizable. In fact, the sentence that follows your quoted sentence cites two commonly known physical limitations that prevent the existence of your "computational class above and beyond Turing". Whether or not there exist physically realizable computations that are not computable by a turing machine is an open question, but most physicists and computati…
Read unlimited as arbitrary precision. I'm familiar with the Turing thesis but he's wrong.
Care to elaborate?
Re: Analog Computers
#40Earlier quoted context omitted.
What you're describing is generally accepted to be physically unrealizable. In fact, the sentence that follows your quoted sentence cites two commonly known physical limitations that prevent the existence of your "computational class above and beyond Turing". Whether or not there exist physically realizable computations that are not computable by a turing machine is an open question, but most physicists and computati…
Read unlimited as arbitrary precision. I'm familiar with the Turing thesis but he's wrong.
> I'm familiar with the Turing thesis but he's wrong.
You're going to have to back up a statement like that with a whole lot of supporting evidence if you want to be taken seriously.