Re: Issue using UPC on Opteron Cluster

From: Alexandre Chauvin (alexandre.chauvin_at_gmail_dot_com)
Date: Fri Nov 03 2006 - 06:13:42 PST

  • Next message: Dan Bonachea: "Re: Issue using UPC on Opteron Cluster"
    Thank you Dan for this quick reply. I will give it a try even if I saw that
    I have to download the Beta version 2.3.16 of UPC to be compatible with PPW.
    I was trying with version 2.2.2 so far.
    I will keep you updated.
    Another quick question is that I am facing some difficulties to allocate
    more than 1.3GB of RAM per thread with the vapi conduct. Can U see any
    explanation for that?
    On 11/3/06, Dan Bonachea <bonachea_at_cs_dot_berkeley_dot_edu> wrote:
    > Hi Alexandre -
    >    This is a common experience for UPC programs that are written in a
    > shared-memory style without regard for locality, when run for the first
    > time
    > in a distributed-memory environment (where locality is extremely important
    > for
    > good performance, because communication is orders of magnitude more
    > expensive
    > across nodes than within a shared-memory node).
    >    Chances are you have some communication-related performance bugs in
    > your
    > application - possibly due to the layout of your main data structures, but
    > possibly also just communication "leaks" from accidental or trivial
    > sharing of
    > data where things need to be tuned.
    >    Luckily, we now have a very nice performance tool designed specifically
    > to
    > help UPC programmers find and fix such problems, called the Parallel
    > Performance Wizard:
    >    I strongly encourage you to download it and give it a try. The PPW team
    > is
    > very receptive to feedback about the performance tool, and probably would
    > even
    > help you to track down your performance issues if they aren't immediately
    > obvious in the tool output.
    > Hope this helps..
    > Dan
    > At 01:30 AM 11/3/2006, Alexandre Chauvin wrote:
    > >Hello All --
    > >
    > >I am facing some issues when trying to run a UPC code on an Opteron
    > Cluster
    > >environement. I am quite newbie with UPC so the answer could be very
    > trivial.
    > >Could you please have a look?
    > >
    > >I would like to use my whole cluster to do a sort. But, if the code goes
    > very
    > >fast when using 8GB memory with pthreads within a single node, it goes
    > very
    > >slow as soon as I try to use multiple nodes.
    > >
    > >I tried both vapi and mpi conducts -- infiniband interconnect -- but
    > >performance was very bad. It went from 1min on 1 node to more than 20mins
    > >when using 2nodes!
    > >
    > >
    > >Is it something particular I should do to use multiple nodes mode
    > >efficiently?
    > >

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