2 Replies Latest reply on May 11, 2007 12:14 PM by Francesco Rustichelli

    How many cores is too many?

      Now that cosmos can work with multiple processors, how many is good enough?
      My analysis I'm running today has 930,000 DOF, 11 bodies total, 5 bonded surfaces, 5 contact surfaces, and 4 bolted surfaces each held with 12 bolts. 6 bodies are steel, 5 are nylon, so I am running direct sparse solver.
      This is a big simulation and is at 35% after 2 days running on dual core machine with Windows XP Pro (32-bit), 3GB ram, two 3.4GHz Xeon chips.
      I'm going to get a new computer because I will have lots of analyses more or less about this size. The IT people are considering Windows XP-64 bit, 8GB or 16GB of Ram, and perhaps 4 or even 16 processor cores. Then my neighbor mentioned that FEA is notorious for suffering from diminishing returns from multiprocessing, that perhaps 4 cores is already too much and 16 cores is likely too much. Anybody have any background on this topic?
      The question is, is 16 cores too much? 4 cores too much?
      Thanks greatly for your consideration.
        • How many cores is too many?
          Chris Michalski
          Kevin - not sure if you're still debating this, but I can tell youfrom working with one of the engineers at FloWorks on other issuesthat multi-core is only going to help you run multiple simulationsat once - 1 simulation, 1 processor core - as for the 32-bit/64-bitthey found it generally lets you run larger models (more nodes) butactually increases simulation time - my P4 3.6 never touches mostof the 4GB of RAM it's got during simulations (some up to aweek) - the consensus I've found was to spend the extra cashon a processor chiller and overclock it instead of loading it withRAM and multi-processor setups - not an easy solution but the bestfor breakneck speed or large simulations
          • How many cores is too many?
            Francesco Rustichelli
            Kevin, CosmosWorks can use very well 2 cores (NOTE: FFE+ and Sparsefor STATIC)

            I do not have official data but I believe it cannot use morecpu's yet.
            I do not know anybody who has tried 4 cores.

            Please note that CosmosFloWorks is different.
            Chris's answer is correct but applies only to FloWorks.

            Anyway using a double or quicker CPU is useless if you donot have enough RAM.
            930'000 DOF need about 400 MB ram with FFE+ and 4GBram with Sparse.

            So if you cannot simplify your model (or mesh), you have to useFFE+ or upgrade to a 64bit PC with at least 4 or 6GB ram.

            When your Cosmos stays completely in ram and not in VM,
            then you can think about the speed (or the number) of the CPU's.