Dear Meep users, I want to buy a new computer (or a small workstation if that will be the best deal) for running numerical calculation - among which Meep. Maybe with two processors, but first I want to get some information and orient myself on the various options: if possible, I would like to get some hints on which may be the best chip (given some reasonable price constraints) for running Meep-MPI. I plan to run models with size of a couple of Gb.
I have asked around, and someone told me that, since a FDTD code needs to read the whole field from RAM at every cycle, then the most important consideration for a fast system is actually RAM speed; and second the processor should be somehow adapted to the speed of the memory, requesting RAM data at exactly the same speed at which RAM is able to supply them: if the processor asks data more quickly than that the result is worse performance. Can someone confirm/comment on this? The second consideration, that I saw in a past thread on Meep-discuss (http://www.mail-archive.com/meep-discuss@ab-initio.mit.edu/msg02357.html) is that MPI is not designed in particular for multicore systems, that have shared memory, but for multiprocessor systems in which each processor has its own memory (or a separate connection to the memory, I have not understood well). In fact for the about 1 Gb model that I am running now, using OpenMPI (the one that I found pre-installed on the Macbook Pro I own: I haven't yet checked how things work if I install the current version of OpenMPI) on a Core2 duo, I get a very small performance improvement with respect to the single processor Meep (each step runs in about 0.75 seconds with two processes rather than 0.80 seconds on the single-processor version). I read in that thread that Corei7 processors should be substantially better from that point of view. Can someone comment? Should one go for a Corei7 or a Xeon processor? Thanks in advance, Giovanni ---------------------------------------- Message sent by Cup Webmail (Roundcube) _______________________________________________ meep-discuss mailing list meep-discuss@ab-initio.mit.edu http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
