[Paraview-developers] Threading

[Berk Geveci]

Hi Alan,

I don't think that this is exactly accurate. What they have done is to use
threaded parallelism within each MPI rank in the cases where there are
multiple blocks/parts to parallelize over. Meaning that they parallelize
each filter's execution over blocks using posix threads. For example, a CTH
dataset would benefit from a similar approach in ParaView (which we can
also support). On the other hand, the way we load Exodus, we don't generate
enough blocks to parallelize over so this approach would not result in any
performance improvement.

Also, I very seriously doubt that they experience any significant
performance improvement (if any) over using multi-threaded parallelism over
MPI. Meaning if they used as many MPI ranks as threads on each node, I
would bet that the performance would be comparable. This will not continue
to be the case as the number of cores increase but it still holds for the
kind of workload we have. Using threads reduces memory overhead however.

We have been exploring parallelism in similar ways both through VTK and
VTK-m and I expect to see ParaView benefit from this work starting this
summer. So don't worry :-)

-berk


On Fri, May 16, 2014 at 3:57 PM, Scott, W Alan <wascott at sandia.gov> wrote:

>  Utkarsh/All,
> I head that VisIt started communicating between different cores/ processes
> on a single node using interthread communication (rather than MPI).  I
> would assume this is using openMP or some such.  Anyway,  my notes also say
> that they picked up a 2x speedup.  Would it be worthwhile moving ParaView
> to not use MPI to communicate within a node?  As nodes pick up more and
> more cores, this may become more important.
>
> Alan
>
>
> --------------------------------------------------------
> W. Alan Scott
> ParaView Support Manager
>
> SAIC
> Sandia National Laboratories, MS 0822
> Org 9326 - Building 880 A1-C
> (505) 284-0932   FAX (505) 284-5619
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