[mpich-discuss] Help Mpich2

[Ricardo Román Brenes]

agreed, i meant for openMP and shared memory architectures

On Mon, Jul 9, 2012 at 7:45 PM, Jeff Hammond <jhammond at alcf.anl.gov> wrote:

> hyperthreading is almost universally terrible for HPC.  it's disabled
> in every supercomputer i've ever used.
>
> very few codes are sufficiently threaded for MPI+OpenMP to pay off
> except when they are memory- or bandwidth-limited.  otherwise Amdahl's
> Law prevails and process-based parallelism wins.
>
> jeff
>
> On Mon, Jul 9, 2012 at 8:22 PM, Ricardo Román Brenes
> <roman.ricardo at gmail.com> wrote:
> > according to my reserches, it all depends on your network and processor
> > type. If u got a fast network, really fast not 1GB ethernet... you can
> > "sacrifice" the transfer time. If you got a processor with hyperthreading
> > its possible that ur threads run faster
> >
> > On Mon, Jul 9, 2012 at 6:37 PM, Pavan Balaji <balaji at mcs.anl.gov> wrote:
> >>
> >>
> >> On 05/26/2012 06:43 PM, angelo pascualetti wrote:
> >>>
> >>> How many processes (-np) should tell mpich to be faster than openmp?
> >>
> >>
> >> There's no way we can answer this question.  Depending on the
> application,
> >> either MPI-only or MPI+OpenMP can be faster.  MPICH supports both
> models, so
> >> you can experiment with them.
> >>
> >>  -- Pavan
> >>
> >> --
> >> Pavan Balaji
> >> http://www.mcs.anl.gov/~balaji
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> >
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>
>
> --
> Jeff Hammond
> Argonne Leadership Computing Facility
> University of Chicago Computation Institute
> jhammond at alcf.anl.gov / (630) 252-5381
> http://www.linkedin.com/in/jeffhammond
> https://wiki.alcf.anl.gov/parts/index.php/User:Jhammond
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