--- 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 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 costs $2 million/month > just for electricity for their server farms. Google > is building a > supercomputer in Oregon that will have cooling > towers 4 stories high. > http://en.wikipedia.org/wiki/Project_02 > > > > > --- Matt Mahoney <[EMAIL PROTECTED]> wrote: > > > > > --- Eugen Leitl <[EMAIL PROTECTED]> wrote: > > > > > Google already have enough computing problem > to > > > do a crude simulation of a > > > [human brain] > > > > > > > > Um, no. It takes 64 kNodes of Blue Gene/L to > do > > > about 8 1/10th speed > > > > crudely-simulated > > > > mice, or about one realtime cartoon mouse > > > (assuming, the code would scale, > > > > which it > > > > wouldn't). > > > > > > The Blue Gene/L simulation is at a lower level > than > > > is needed to do useful AI. > > > You don't need millisecond resolution. In most > > > neural models, the important > > > signal is the rate of firing, not the individual > > > pulses. I realize there are > > > exceptions, such as the transmission of phase > > > information for stereoscopic > > > sound perception up to 1500 Hz. But for most > > > purposes, neurons have an > > > information rate of about 10 bits per second. > This > > > was measured in tactile > > > sensation in the finger. (Sorry I don't have > the > > > references). In any case, > > > 0.1 seconds is about the smallest perceptable > time > > > unit in humans. > > > > > > The human brain has about 10^11 neurons with > 10^4 > > > synapses each. Each synapse > > > represents about 1 bit of memory (Hopfield > model). > > > Therefore you need 10^15 > > > bits of memory and 10^16 operations per second. > > > > > > Google has about 10^5 PCs with 2-4 GB memory > each, > > > connected by a high speed > > > Ethernet. Therefore they have enough memory. > They > > > have a mix of different > > > processors, but a modern processor can execute > 10^10 > > > to 10^11 16-bit > > > multiply-add instructions per second using SIMD > > > (SSE2) instructions (more if > > > you add a GPU). Therefore they have enough > > > computing power, or at least close > > > enough to do useful experiments. > > > > > > > > > > > > -- Matt Mahoney, [EMAIL PROTECTED] > > > -- 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/?&; > ____________________________________________________________________________________Looking for a deal? Find great prices on flights and hotels with Yahoo! FareChase. http://farechase.yahoo.com/ ----- 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
