[extropy-chat] Desirability of Singularity (was Are ancestor simulations immoral?)

[Martin Striz]

On 6/5/06, Anders Sandberg <asa at nada.kth.se> wrote:

> > What is the conversion you're using (i.e. J/spike)?  How do you derive
> > it?  Are you taking the total energy demands of a neuron over time
> > divided by the average number of spikes over the same time?  Or are
> > you counting just the thermodynamics of the axon and boutons?
>
> The Brillouin inequality states that if you erase one bit of information
> you have to at least pay an entropy cost of kT ln(2) Joules (where k is
> Boltzmann's constant and T is the temperature). This is of course a lower
> bound, being the reduction of entropy a bit erasure represents. A synapse
> having probability p of failing will on average erase -pln(p)/log(2) bits
> of information for each signal. Hence  N synapses receiving f signals per
> second will require at least -NfkTp*ln(p) J/s.

Gotcha, so you're assuming a computational substrate that has zero
energy demands other than for information erasure according to the
Brillouin inequality.

> > I'm not sure what you're comparing here, what a neuron could
> > accomplish if all of its energy input were used for computation rather
> > than metabolism (and minimal loss as heat)?  Or are you suggesting
> > that there's energy loss somewhere else?
>
> This would be the energy needed to run a thermodynamically perfect replica
> of the brain, with neurons not requiring any energy to run and just
> information erasure losses.

Understood now, but what's the point?   To say that evolution is X%
inefficient with respect to some idealized (and impossible) substrate
is rather uninformative.

Are you trying to use that as a canonical  metric for comparing any
future computational substrate?   A perfect computational substrate,
i.e. one that also has zero information erasure, runs on zero energy.
:)  Have I said anything interesting?

I thought a useful calculation would be to determine how efficient you
could make cells for computation, but that of course is unknown.
Neurons, as it happens, are probably greater than 90% efficient with
respect to /their design/, i.e. there's little heat loss.

Martin