--- Tom McCabe <[EMAIL PROTECTED]> wrote: > > --- Matt Mahoney <[EMAIL PROTECTED]> wrote: > > > > > --- Tom McCabe <[EMAIL PROTECTED]> wrote: > > > > > You cannot get large amounts of computing power > > simply > > > by hooking up a hundred thousand PCs for problems > > that > > > are not easily parallelized, because you very > > quickly > > > run into bandwidth limitations even with gigabit > > > Ethernet. Parts of the brain are constantly > > > communicating with one another; I would be very > > > surprised if you could split up the brain > > effectively > > > enough to be able to both run one tiny piece on a > > PC > > > and have the PCs communicate effectively in > > realtime. > > > > > > - Tom > > > > It is not that hard, really. Each of the 10^5 PCs > > simulates about 10 mm^3 of > > brain tissue. Axon diameter varies but is typically > > 1-2 microns. This means > > each bit of brain tissue has at most on the order of > > 10^7 inputs and outputs, > > each carrying 10 bits per second of information, or > > 100 Mb/s. This was barely > > within Google's network capacity in 2000, and > > probably well within it now. > > http://en.wikipedia.org/wiki/Google_platform > > Hmmm...This is an interesting issue. Do you have a > link to a paper on brain bandwidth?
I just googled "axon diameter" and found several references. There is a wide range so I used the low end to be conservative and did the math. I probably should consider dendrites too, but these tend not to be very long. I figure it's close enough for an order of magnitude estimate. > > I think individuals and small groups trying to build > > AGI will have a hard time > > competing with Google due to the cost of hardware. > > Hardware cost will not be a primary issue. The cost of > hardware decreases exponentially with Moore's Law; the > cost of solving a whole tangle of confusing problems > does not. Nobody is anywhere near the stage where they > have a program to run and they're looking for a > computer. It's like saying that anyone trying to build > an airplane will find it impossible to compete with > existing shipbuilders, because of their vast > metalworking capacity. It's true we can do theoretical work but the lack of computing power is definitely an obstacle. It has a strong effect on the direction of research. In the early days of AI when hardware was inadequate by a factor of a billion, we used symbolic approaches in narrow domains with hand coded rules. More recently when hardware was only inadequate by a million, we were able to experiment with statistical approaches, machine learning, and low level vision and language models. It is possible that a lot of the brain's computing power is used to overcome the limitations of individual neurons (speed, noise, reliability, fatigue) and we will find more efficient solutions. This hasn't happened yet, but I can't say that it won't. -- Matt Mahoney, [EMAIL PROTECTED] ----- This list is sponsored by AGIRI: http://www.agiri.org/email To unsubscribe or change your options, please go to: http://v2.listbox.com/member/?member_id=4007604&user_secret=8eb45b07
