[mpich-discuss] Faster MPI_Attr_get?

[Jed Brown]

On Fri, May 11, 2012 at 4:03 PM, Dave Goodell <goodell at mcs.anl.gov> wrote:

> On May 11, 2012, at 1:49 PM CDT, Dave Goodell wrote:
>
> > On May 11, 2012, at 1:17 PM CDT, Jed Brown wrote:
> >
> >> Can you make this fast, like ~100 clocks for the common case?
> >
> > Can you send us a small benchmark that you would like us to optimize?
>  Presumably you already have one since you've measured the overhead.
>

I benchmarked an example using the PETSc ThreadComm. For a micro-benchmark
that doesn't use pthreads, I would just call MPI_Attr_get() in a loop. I
can prepare that if you like.


> >
> > If the current performance is really ~1000 instructions I suspect we can
> easily knock it down by a large factor.  I'm not sure whether 100 is
> realistic or not until I play around in there some more.
>
> Also, please send me the configure options that you are using for your
> MPICH2 under petsc.  The absolute performance is going to vary
> substantially depending on whether error checking is enabled and your
> choice of a few other options.
>

I tested these two configurations, what do you suggest I use if I want that
function to be fast?

MPICH2 Version:         1.4
MPICH2 Release date:    Thu Jun 16 16:41:08 CDT 2011
MPICH2 Device:          ch3:nemesis
MPICH2 configure:       --prefix=/opt/mpich2 --enable-shared
--enable-sharedlibs=gcc --enable-error-checking=runtime
--enable-error-messages=all --enable-timer-type=clock_gettime
--with-python=python2
MPICH2 CC:      gcc  -march=native -O1 -pipe  -O2
MPICH2 CXX:     c++  -march=native -O1 -pipe -O2
MPICH2 F77:     gfortran   -O2
MPICH2 FC:      gfortran   -O2

MPICH2 Version:     1.5b1
MPICH2 Release date: unreleased development copy
MPICH2 Device:     ch3:nemesis
MPICH2 configure: --prefix=/homes/jedbrown/usr/mpich-intel --enable-shared
--enable-error-checking=runtime --enable-error-messages=all
--enable-timer-type=clock_gettime CC=icc CXX=icpc --enable-fc=0
--enable-f77=0 FC= F77=
MPICH2 CC: icc    -O2
MPICH2 CXX: icpc   -O2
MPICH2 F77: gfortran
MPICH2 FC: gfortran
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