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Analog computing may be coming back

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Re: Analog computing may be coming back

#51

Post by sbaiddn »

arbuge wrote: post #46
sbaiddn wrote: post #32

Earlier quoted context omitted.

Get a ruler. Draw a line 10 cm long, AB. Now grab end B and draw another another line, BC, with a certain angle $/alpha$ wrt to the first. Now measure the distance AC. Congratulations! You have just built an analog computer to use the Law of Cosines to solve for line segment AC. Non-dimensionalize your result and its a general LofC solver. A problem that (I suspect) would take the majority of modern day Eng undergrad…

The issues arise when converting the analog outputs of those physical experiments back to the digital domain for processing. High speed and resolution analog to digital converters are not cheap, and often require different process node technologies for implementation. The cost savings from the elimination of computing the models digitally have to be weighed against the costs arising from the converters' introduction.

I agree, hence my robots API joke.

Re: Analog computing may be coming back

#52

Post by krastanov »

pantulis wrote: post #43
zozbot234 wrote: post #22

Analog computing sucks. It's inherently sensitive to noise and random variation in your devices that's basically ubiquitous with modern chip-making processes. Digital electronics actively reject noise at every step in a computation, albeit at the cost of wasting energy in the process. With analog, a more complex computation becomes exponentially harder.

Sounds a lot like "quantum computing".

Quantum computing is digital (with error correction), not analog. Analog computing can not scale *in principle*. Quantum computing can theoretically scale (it is not forbidden by the laws of Nature like it is for analog computing), it is just engineeringly "difficult".

Re: Analog computing may be coming back

#53

Post by xor99 »

Analog computers can perform matmul operations without data movement using physical properties such as conductance changes in a very small volume. If noise and random variation can be modelled successfully then in certain cases they are obviously going to be better (e.g. energy use in edge applications). The discussion is not specific enough to applications to be useful. AI data centres are not going to be using this stuff anytime soon for example. On the other hand, you do not want an NVIDIA GPU inserted into your body.

Re: Analog computing may be coming back

#54

Post by dahart »

zozbot234 wrote: post #22

Analog computing sucks. It's inherently sensitive to noise and random variation in your devices that's basically ubiquitous with modern chip-making processes. Digital electronics actively reject noise at every step in a computation, albeit at the cost of wasting energy in the process. With analog, a more complex computation becomes exponentially harder.

One of the potentially large applications for optical analog computing is for training neural networks, which is an application where noise is a feature and is tolerable. People are already using noise (and low precision) intentionally for regularization and also doing things like intentionally not synchronizing GPU kernels for performance, which causes the inputs for the next round to be in a potentially random state when read, and noticing that the regularization side effects on the network are positive.

Re: Analog computing may be coming back

#55

Post by jermaustin1 »

nanna wrote: post #29
silvestrov wrote: post #26

Earlier quoted context omitted.

Analog computers are like LP records: only good for nostalgia.

Depth of sound, long term storage, ease of navigation, there are lots of reasons people prefer vinyl that aren't based in nostalgia.

What do you mean by depth of sound? A vinyl record has a dynamic range of around 70db, where as a CD has a dynamic range of up to 144db, though in practice it is usually only 90-96db. Either way you shake that stick though, digital audio (uncompressed) has a much deeper sound.

Even in the recording studio back in the days of vinyl pressings all ran on studio grade magnetic tape with a higher dynamic range (not by much, albeit), but the sound that the artist was going for was typically hindered by analog recording media in a way that isn't true today.

Re: Analog computing may be coming back

#56

Post by dahart »

noduerme wrote: post #14
choudharism wrote: post #2

The mark of a maturing domain is the evolution from only general tools to general + specialized. We've gone from only CPUs to CPU + GPU to specialized AI chips (Neural Engine, Tensor chips etc.) and specialized computing is a big tent which can fit many different architectures together. Analog computing is the closest thing to bioengineering in fundamental computer science that I know of, so I am confident that it wi…

Maybe I'm missing something, but wouldn't any optical computer have to still funnel signal through binary logic gates at some point? In what sense is that any more analog than (digital recordings on analog) magnetic tape decoded by a modem? The ultimate computation is still 1/0

Digitizing the output of an analog computation doesn’t make it a digital computation. It’s still analog. The ultimate computation is not binary 1/0, it gets converted to binary after the computation. We may be able to save time or energy by changing representation.

Imagine a NxN matrix-matrix multiply. The computation part is (naively) N^3 multiplies. The conversion back to digital is only N^2 operations, and those operations may be much simpler than digital multipliers. If there’s a way to do the N^3 multiplies as analog, then we can potentially save a lot by converting to and from binary to enable the analog phase.

Re: Analog computing may be coming back

#57

Post by adgjlsfhk1 »

orbifold wrote: post #48
staunton wrote: post #15

Earlier quoted context omitted.

> For physics reasons the integration density of optical compute elements is abysmal and will remain so forever. Could you give some details? Claims about "forever" often don't hold up. I guess you're referring to things like component size in relation to the wavelength of light used? One could use smaller wavelengths. Integrated photonics is certainly being done and also commercially relevant (in telecommunications)…

Visible light and near ultra-violet light has a wavelength ~400-800 nm, current gen transistors have a pitch of ~40 nm. This gets worse because scaling is actually either quadratic (2d) or cubic (future 3d integration). So we are talking about 100x to 1000x worse spatial scaling disadvantage at the moment. The only redeeming quality of light is wavelength multiplexing, but that is only useful for a subset of applicat…

100x loss in density isn't actually necessarily a problem. Optical systems have potential for much higher clocks (since there's so much less heat), and the actual logic on a cpu is tiny. If you can get 50ghz clocks, you can lose a lot of density and still win out (I'd take 10x single core perf over 10 cores any day of the week).

Re: Analog computing may be coming back

#58

Post by sbaiddn »

noduerme wrote: post #47
sbaiddn wrote: post #32

Earlier quoted context omitted.

Get a ruler. Draw a line 10 cm long, AB. Now grab end B and draw another another line, BC, with a certain angle $/alpha$ wrt to the first. Now measure the distance AC. Congratulations! You have just built an analog computer to use the Law of Cosines to solve for line segment AC. Non-dimensionalize your result and its a general LofC solver. A problem that (I suspect) would take the majority of modern day Eng undergrad…

>> Now build a robot that measures AC for you and you have an API for your analog computer. This line made me laugh out loud, but what an amazing explanation and set of examples. Thank you. The original ECU in my 1980 Datsun ... is digital, right? I just never thought of the insane analog vacuum pot system that controls the cold start valve and the air conditioning selector and the cruise control to also be a "comput…

Glad to get a chuckle. I was more more proud of my reproducible builds jab.

Does a 1980's Datsun have an ECU? That's not obvious to me. Even a 6502 would be an expensive add on at the time given car margins. Maybe a one bit controller?

But there are analog solutions to all these control situations. And you don't need vacuum tubes!

Measuring and adjusting the fuel-air mix is the carburetor's job. The carb doesnt just add fuel. It adds the right amount of fuel. Its needle calibrates it for different conditions (namely pressure).

The spark advance "computer" was super cool. Originally spark advance was a lever controlled by the user. Faster rpm -> adjust for more advance. Eventually the lever was attached to a governor (a set of balls attached to a spinning linkage and a stiff spring. It measures rpm) and the spark advance disappeared under the hood.

The automatic version of your car would have had a (very complicated) hydraulic circuit in the tranny pushing pistons that measure throttle, rpm, velocity and choose the gear accordingly.

The manual version had a vast organic neural network doing the same job but using just sound pitch of the engine. The manual transmission was cheaper because it didn't include the neural network shifter except on the very highest end cars - think RRs - and then only as a service (early SAS model).

German WW2 aircraft were fuel injected so they probably used a governor attached to the throttle wire and pressure gauge to guesstimate the mass flow and therefore the fuel to inject. There's a front page HN submission - the fuel control system of those engines or the original Mercedes Gull-wing!

All of the hydro-mechanical stuff described were slowly transistorized (but kept analog) in the 70s. In the late 80s to 90s everything became digital except the transmissions that took longer.

Re: Analog computing may be coming back

#59

Post by sbaiddn »

mellavora wrote: post #37
sbaiddn wrote: post #32

Earlier quoted context omitted.

Get a ruler. Draw a line 10 cm long, AB. Now grab end B and draw another another line, BC, with a certain angle $/alpha$ wrt to the first. Now measure the distance AC. Congratulations! You have just built an analog computer to use the Law of Cosines to solve for line segment AC. Non-dimensionalize your result and its a general LofC solver. A problem that (I suspect) would take the majority of modern day Eng undergrad…

> Typically an analog computer is thought of as a set of opamps and diodes, whose currents and voltages solve a set of non-linear ODEs; Oh oh oh! and also resistor/capacitor circuits! Great for integration or differentiation! Integration and differentiation have interesting audio effects; maybe our ears might be one of the better analog computers.

Our senses are incredibly good.

Re: Analog computing may be coming back

#60

Post by tinus_hn »

BitwiseFool wrote: post #49
nanna wrote: post #29

Earlier quoted context omitted.

Depth of sound, long term storage, ease of navigation, there are lots of reasons people prefer vinyl that aren't based in nostalgia.

No DRM and the fact that you actually own it is a big plus.

Like a CD?
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