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From: Chris Barts on 11 Jan 2007 06:18 On Wed, 10 Jan 2007 11:01:57 -0800, Tim Bradshaw wrote: > these codes How many people have forgotten that 'code' is a mass noun and, as such, does not take plurals? Do you also say 'these muds' and 'these dusts'? -- My address happens to be com (dot) gmail (at) usenet (plus) chbarts, wardsback and translated. It's in my header if you need a spoiler. ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =----
From: Tim Bradshaw on 11 Jan 2007 06:37 Chris Barts wrote: > > How many people have forgotten that 'code' is a mass noun and, as such, > does not take plurals? Do you also say 'these muds' and 'these dusts'? How many people have forgotten that *language changes over time* and is not something handed down from the elder days, never to be changed? The sense of `codes' I gave is very common in the HPC community where "a code" typically refers to something approximating to a particular implementation of an algorithm. The plural use, which is more common, means something like "implementations of algorithms" Thus for instance a paper title from 2001: "High-Performance Java Codes for Computational Fluid Dynamics" and many other examples. Note that this use is quite different than the mass noun use "this code" would refer to a *single* program, or some chunk of code from it, while "these codes" would refer to a number of programs, or rather to their computational kernels. And in fact, this usage is fairly similar to the way you might use "these muds" say, to refer to a number of different kinds of mud. I'm quite sure I could find such usages in the geological literature, since I'm already aware of usages like "these shales" to refer to different kinds of shale. --tim
From: Juan R. on 11 Jan 2007 07:05 John Thingstad ha escrito: > > So far as i know the prediction is that at some time in the second half > > of this century, fast supercomputer could only offers us a 1000s MD > > simulation for a _E. coli_ (~ 10^10 heavy atoms). MD simulations are > > very inexpensive and rough. Prediction suggests no accurate _ab initio_ > > model would be available on this century. > > > > My suggestion is to forget Moor's law. > Computing increase in power increase has been decreasing for some time. > Growth is no longer exponential but scalar. > Say, a quad core CPU has 180% the speed of a single core. > Amdahl's law (wikipedia) Yes, prediction was done over an exponential rise. Of course, if rise is linear in next decades then we will not see MD simulation for E. coli in this century, and no _ab initio_ simulation for many many many time. I believe that the law you cite is asumming that parallelizable task in of order N^0 and i do not agree because do not account for synchronization issues between cores is N dependant. Topologically, performance is approx. [N * 100] - [b * [ [N * [N - 1]] / 2] ] Assuming 60-70% for general tasks for the Opteron dual-core [1], one obtains b = 35. Therefore for quad systems performance would be of order of 190% for Opteron. More realistic formula may account for N dependence on b and for real topological design, for instance if topology for 8 cores is C-C-C-C |x| |x| C-C-C-C then above formula does not apply. Performance would be of order 240%. Note that two perfect parallel quad systems it would be 190 * 2 = 380% [1] http://www-03.ibm.com/servers/eserver/opteron/pdf/IBM_dualcore_whitepaper.pdf
From: John Thingstad on 11 Jan 2007 07:39 On Wed, 10 Jan 2007 16:56:29 +0100, pTymN <ptymn1447(a)gmail.com> wrote: > I work in the video games industry, and I think that multicore > processors are going to kill the PPU (physics processing unit) cards > that Aegia is trying to release. For the foreseeable future, more > realistic collision detection and particle based physics will happily > consume as many processors as we can throw at the problem. It will not > be cheap to add interactive fluids to a game, and this is one problem > that requires fairly random memory access, so GPUs won't be as useful. > > I work on Gamebryo, and we recently parallelized our physics and > collision libraries. Triangle mesh to triangle mesh collisions are > computationally expensive and can be done in parallel. > Sorry! This was never supposed to end up here.. -- Using Opera's revolutionary e-mail client: http://www.opera.com/mail/
From: John Thingstad on 11 Jan 2007 07:43
On Thu, 11 Jan 2007 13:05:17 +0100, Juan R. <juanrgonzaleza(a)canonicalscience.com> wrote: Nop. The numbers are gotten from Amhdal's law. They are also the numbers Intel use! (180%) Yes, they are approximate. Obviously. -- Using Opera's revolutionary e-mail client: http://www.opera.com/mail/ |