Re: Run Code on Multiprocessors

Date: Tue Nov 29 2005 - 22:14:41 PST

  • Next message: Rafik Salama: "Installation GCC error"
    On Tue, Nov 29, 2005 at 08:27:35PM -0700, Sirisha Muppavarapu wrote:
    > Hi...
    > When I run my upc code, it says, 
    > WARNING: Node 0 running more threads (4) than there are physical CPU's (2)
    >          enabling "polite", low-performance synchronization algorithms
    > -----------------------------------------------------------------------
    > I compiled my code with T=4 i.e 4 threads. The system is a linux system with 2
    > processors. Can anyone plz suggest how to force the threads to run on all the
    > processors of the machine and not just 1 processor. How do I make sure that
    > code is indeed running on/using multiprocessors?
    Both CPUs *are* being used, unless I'm missing something.  Do you have
    evidence that only one is used?
    The message above simply says that you're running 4 UPC threads on 2
    CPUs.  In this case, to avoid poor spin-lock performance, we revert to
    using pthread mutexes, which are more expensive in a contention-free
    situation, but much more well-behaved when contention is present.
    Jason Duell             Future Technologies Group
    <jcduell_at_lbl_dot_gov>       Computational Research Division
    Tel: +1-510-495-2354    Lawrence Berkeley National Laboratory

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