Re: Berkeley UPC XT3 support

From: Dan Bonachea (bonachea_at_cs_dot_berkeley_dot_edu)
Date: Tue Sep 13 2005 - 13:24:20 PDT

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    At 10:12 AM 9/13/2005, Adrian Powell wrote:
    >      I noticed in the 2.2.0 ChangeLog that it says to get in touch with you 
    > all for XT3
    >queries....    What's the deal with XT3 support ?.
    Hi Adrian -
       The reason we don't directly encourage users to try BUPC 2.2 on XT3 is that 
    our XT3 port is brand-new and all we've done so far is a "phase 1" port, where 
    all UPC communication on that machine is performed using calls to an MPI-based 
    compatibility layer. Consequently, the communication performance for BUPC 
    programs on XT3 is currently somewhat worse than can be achieved by writing 
    applications directly in MPI. However, we've recently opened a contract with 
    Cray to do a "native" GASNet implementation on XT3, which will allow us to 
    bypass the MPI layer and deliver communication performance for UPC programs 
    comparable to (or hopefully even superior to) programs written directly for 
    MPI. That support will likely be included in the next release.
       So basically we want to ensure any Berkeley UPC users trying out the XT3 
    understand that our XT3 support is still very much a "work-in-progress" and 
    doesn't yet deliver the performance we expect to eventually provide on the 
    XT3. This is mostly just an attempt to head off any potential for unfair 
    performance comparisons by outside groups who may "discover" that BUPC on XT3 
    doesn't currently deliver the peak network performance.
       Provided you understand all this and are still interested in trying out the 
    initial XT3 port, I can send you the additional file (not included in the 
    distribution) that you'll need to do the build.
    >    Thanks,  Adrian.

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