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Analog Computers

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Re: Analog Computers

#21

Post by adamnemecek »

mgraczyk wrote: post #20
adamnemecek wrote: post #17

I'm hoping that analog computing will come back in the form of photonic analog computing. This would be more powerful than quantum digital computing (you know the things that people are wasting time on). Fun fact, with analog computing, one could imagine achieving Real Computation ( https://en.wikipedia.org/wiki/Real_computation ) which is above and beyond Turing. completeness. Note the fun sentence "If real computat…

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.

Re: Analog Computers

#22

Post by mindcrime »

smellf wrote: post #18
mindcrime wrote: post #6

If any of you guys are into analog computing, just as an FYI, there's a sub-reddit dedicated to the topic (full disclosure, I started this particular one). analogcomputing.reddit.com There's not a ton of content there yet, but please feel free to add anything you come across. I'm a fan of the idea and suspect, like the author of this piece, that there is "something there".

How long have subreddits been accessible through a subdomain? Is this something the subreddit mods have to turn on?

For as long as I can remember and I've been using Reddit since about 2008.

Re: Analog Computers

#23

Post by mindcrime »

xfer wrote: post #15
mindcrime wrote: post #11

Earlier quoted context omitted.

The author's so called analog computers Why do you say "so-called"? can be built by using FPGAs. Also, FPAA's (Field Programmable Analog Array)[1] [1]: https://en.wikipedia.org/wiki/Field-programmable_analog_arra...

Maybe it was the wrong term. My point was we have them and they are used, but they are not cost efficient in general. So saying that they will be the future of computing, is a bit ridiculous imo.

Fair enough. I think they will be part of the future of computing, but saying they are "the future of computing" is probably hyperbole.

Re: Analog Computers

#25

Post by robotresearcher »

cr0sh wrote: post #16

A 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.

Re: Analog Computers

#26

Post by robotresearcher »

Miky wrote: post #14
xfer wrote: post #7

The author's so called analog computers can be built by using FPGAs. And the term he might be reaching for is called data-flow programming.

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 machine.

Even an Intel i7 chip is an analog machine that approximately implements the i7 computer design. They throw away the ones that don't approximate it up to tolerance.

Re: Analog Computers

#28

Post by janekm »

Analog 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?).
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