X-Message-Number: 26964 From: Date: Thu, 8 Sep 2005 02:44:51 EDT Subject: Sequential and parallel processing This is more to Donaldson, but other could find if they agree or not. For me, there is no magic in parallel processing, our brain make a lot of sequential work along dendrites and from neuron to neuron. The basic function of a neural network is sequential. Now, given the slowness of electrochemical signals, a lot of parallelism must be used in the brain. There is hardly any information processing in the brain with time constant smaller than one millisecond. Current electronics processors have a clock cycle smaller than one nanosecond, one million time faster. A single material electronics unit can so process one million more informations in a given time that the biological electrochemical system. For a given problem, that shift the sequential-parallel mix on the sequential side. That is not to say that actual electronics chips are fast enough to do everything on a single sequential processor. When I have told that a chip could contain one thousand neurons (this is parallel processing), Mr. Donaldson insisted that there must be only one neuron per chip, so he advocated an extreme form of sequential processing... In fact, a brain simulation is a big problem but not even what mathematicians call a hard one, such the salesman traveler. Anyway, the sequential-parallel option is something having a meaning only for general purpose computers. As I have said many time, only the slowest currents, varying one the tens of seconds scale would be processed by such devices. Anything faster would be taken into account by FPGAs (where you hardly define sequential and parallel processing) or specialised neuromorphics chips mixing numerical and analog computing. Clearly, the opinion of Mr. Donaldson is purely theoretical and has no relevance to practical desing at least in the uploading frame. YB. Content-Type: text/html; charset="US-ASCII" [ AUTOMATICALLY SKIPPING HTML ENCODING! ] Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=26964