Bad Performance on Power4/AIX

Axel akoh... at gmail.com
Mon Oct 29 21:56:01 CET 2007



On Oct 29, 9:28 am, jschmidt <jochenc... at googlemail.com> wrote:
> Hi,
>
> I've just compiled CP2K on a system with Power4-processors
> ("Regatta"), running under AIX, and there is a problem with the
> parallel version. The sdbg and sopt is fine, but as soon as I switch
> to pdbg or popt (using the arch-files from the cvs) the timings are
> really bad. A system with one water molecule needs about 100 secs

hi,

have you checked that a) you are not running across multiple
regatta frames (=> network overload) or b) you actually have
requested and been granted access to multiple cpus to run in
parallel on and c) have enough memory to not run into permanent
swapping/paging. the latter would easily explain a 100x increase
in runtime.

cheers,
    axel.

for
> initialization and again about 100 secs per MD step. Using the sopt-
> version this is only about 1 sec. Here is the arch-file that I used:
>
> PERL     = perl
> CC       = cc
> CPP      = /usr/ccs/lib/cpp
> FC       = mpxlf95_r -qsuffix=f=f90
> LD       = mpxlf95_r
> AR       = ar -r
> DFLAGS   = -D__AIX -D__ESSL -D__FFTSG -D__FFTESSL\
>            -D__parallel -D__BLACS -D__SCALAPACK
> CPPFLAGS = -C $(DFLAGS) -P
> FCFLAGS  = -C -g -q32 -qarch=pwr4 -qflttrap=overflow:zerodivide:enable
> \
>            -qfullpath -qinitauto=FF -qnointlog -qnosave -qsigtrap -
> qtune=pwr4
> LDFLAGS  = $(FCFLAGS) -bnoquiet
> LIBS     = -L /afs/ipp/@sys/lib -lscalapack\
>            /afs/ipp/@sys/lib/blacsF77init_MPI-POWER4-0.a\
>            /afs/ipp/@sys/lib/blacs_MPI-POWER4-0.a -lessl\
>           -L/afs/rzg/@sys/lib -llapack-essl -lessl -lpessl -lmass -
> lhmd
>
> OBJECTS_ARCHITECTURE = machine_aix.o
>
> Is anyone using the latest cvs-version on a such a system?
>
> Thanks for your help!
> Jochen




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