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

Jason Resch jasonresch at gmail.com
Sun Apr 23 21:23:49 UTC 2023

On Sun, Apr 23, 2023, 1:32 PM spike jones via extropy-chat <
extropy-chat at lists.extropy.org> wrote:

> -----Original Message-----
> >...> On Behalf Of Ben Zaiboc via extropy-chat
> ...
> >...At some point, surely, someone will start getting plausible answers to
> questions like 'How do we achieve practical fusion power plants/space-based
> solar power/drexlerian nanotechnology/mind uploading/indefinite
> life-extension/abundance economy for those who want it/give everyone in the
> world a chance to lead the lives they want to lead while simultaneously
> preventing any megolomaniac fuckheads wiping us all of the face of the
> earth, etc.?...I mean, what's the point of a superintelligence if it can't
> help with any of those?  Ben
> _______________________________________________
> Thanks Ben, great introduction for me to restart a discussion we had for
> years in this forum, and ask for new insights from the GPT jockeys among us
> please.
> When he was still with us, Robert Bradbury used to come to the west coast
> periodically and work with me on the mechanical details of Matrioshka
> Brains.  I am sorry to report that since he passed on, I have made little
> progress on the idea.  My last formal presentation on that topic for an
> engineering group was made in 2011.

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

  I do not know if anyone has worked on the idea since then, as I have been
> caught up in real-world matters such as parenthood.
> Question for our GPT hipsters please, or anyone else who wishes to comment:
> Given a Matrioshka Brain ring with each processor consuming the power
> which can be generated by 100 cm^2 of solar cells at 1 AU (we can go with
> about 20 mW as a reasonable conservative estimate (well below the record
> with current technology))

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.

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.

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.

> What I have described in the paragraph above is the most recent (about
> 2016-ish) BOTEC design of a single ring of a Matrioshka Brain.

I would tend to think a civilization able to build one would be able to
achieve computational substrates much closer to the maximum theoretical
physical limits.

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.

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.

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.

Newer more efficient but slightly less capable GPTs can run on modern
desktops with good graphics cards (perhaps needing a few hundred watts to
run at acceptable near real time speeds.)

and the thermodynamics problems with a Matrioshka Brain are far from
> resolved.

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

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).

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