[ExI] matrioshka brains again, was: RE: Symbol Grounding

Sun Apr 23 23:38:51 UTC 2023

…> On Behalf Of Jason Resch via extropy-chat
…Cc: Jason Resch <jasonresch at gmail.com>

…

>…Do you have a copy of this available online? I am interested…

I don’t, but I do have a website now, with almost nothing on it, so I will find a way to digitize that content and put it on there.  Thx for the good idea Jason.

>…Isn't incident solar radiation at 1 AU around 1300 W? 100 cm^2 should have 13 W available. I'm just making sure I'm not missing something, not sure why your estimate is 3 orders of magnitude less than my rough estimate…

I accounted for the considerable shielding required for any super-long-lived solar cell, but I probably over-accounted.  Significant spectral filtering is needed, as well as a physical barrier for micrometeoriods.  I am assuming being away from earth orbit to reduce space debris problems, but we need something that will produce power with a half-life of a thousand years or more.  Even then, it isn’t entirely clear to me what technology is needed for adequate shielding from cosmic rays, which punch right on thru your favorite mechanical barrier.

with a minimum latency between adjacent nodes of about 3 microseconds,

>…A node here is a processor/solar cell pair? If so they should be ~10 cm from each other. At c the latency would be 3 nanoseconds rather than microseconds, but I think I am missing something…

Eh, that’s what I get for doing this all from memory rather than recalculating, or even doing the dang calcs in my head to see if they are about in the right order of magnitude.  Oh the ignominy, oy vey, sheesh.  

My strawman design had nodes spaced at 1 meter, so inherent latency would be 3 nanoseconds.  Thx for the sanity check Jason: no sanity was detected.

with a cell-phone-ish 256GB of on-board memory per node, and given a trillion such nodes, can we park an effective GPT-4 chatbot on that? 

>…GPT-4 has a trillion parameters. At 8 bits per parameter you should be able to park it across 4 such nodes…

OK here’s the design challenge.  There is a tradeoff between memory availability, power use of the processor, signal bandwidth between nodes, and I do not know how to optimize that function other than just try some combinations and see how it works.  What I don’t know is how to optimize GPT with regard to number of processors, capability of each processor and so on.

>…My last estimates on this (using 2020 numbers) was that we're about 10^34 away from the best physically possible computers. So Moore's law has another 115 years left to go…

OK well, it might require AI to figure out how to do it, for it appears we are approaching the limits to what BI can do with electronics, at least for now.

>…Using 2016 tech estimates for such megastructures, feels to me a bit like a 1910 estimate of how many bits we could store in the future given the constraints that forests impose on the number of punch cards we can make…

Ja, I have found the work on this generally disheartening without Robert’s constant goading and schmoding (he was a rather insistent chap when he wanted calculations done (a process I refer to as Bradburyish goading and schmoding.))

Never mind the other rings for now, let's look at just one ring, for I am told GPT4 needs jillions of processors to do its magic, 

>…So long as the memory is there, you could use a pocket calculator to run GPT-4. It would just take a long time to produce its response…

Ja, I don’t think the current GPT-4 is what we need on there eventually, but I don’t understand the memory/processor balance with the transformers or really even how to estimate that.  I am told Elon is buying these GPUs and such, but at some point we need a collaborator who does understand that balance for working LLMs and other types of calculations.

…

>…Isn't thermodynamic efficiency just a matter of the fraction of the sky filled with star vs. the fraction of sky with ~3K vacuum?

Robert thought so, but I fear that he persistently failed (or rather he flatly refused) to take into account something important: the thermal gradient.  I worked for a while on estimating that using Bessel functions, but eventually gave up on that approach because it was too easy for me to punch holes in my own reasoning.

>… If I remember correctly then a Dyson sphere can at best utilize 50% of the energy present in the solar radiation. A ring, assuming rings don't fill most of the sky (from the point of view of the node on the ring) should be able to use closer to 100%...

Disagree, but if you have some calculations which would return the equilibrium temperature of the innermost nodes, I am all eyes.  The Bessel function approach predicts the inner nodes get hotter than blazes unless the entire device (collection of devices?) is quite diffuse.  This might not be a problem, in fact I think it is a solution.  It is a solution which comes with a cool bonus: it would explain why, if these things exist somewhere, we have never seen one, when they would be easily detectable if they used even 50% of the energy from the star (because it would have a weird-looking spectral signature.)

Robert and I never did agree on this while he was with us.  But for one ring, we don't care about that open question.  Thermodynamic details cheerfully available on request.

>…A single ring has as much space as it needs behind the ring for a long tail of a heatsink. I wouldn't imagine cooling a single ring would be much of a problem. But the temperature the computer operates at does set a floor on the efficiency of irreversible computations (by Laundauer's limit).  Jason 

Ja of course, but with a single ring we don’t care about heat sink capabilities.  We couldn’t overheat if we tried.  Even with a single shell, which consists of a billion rings, thermal considerations are irrelevant.  A billion rings with a trillion nodes per ring, if they can’t figure out the thermal heat sink problem, then we are just busted.

So let’s set aside the heat sink problem for now and just think about how to optimize one ring, or even a slightly different problem: see what happens with a million nodes co-orbiting a common barycenter.

spike

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