[Paraview] distributed stream tracer scalability issue

[burlen]

Hi Dave,

Thanks for the insight and great citation, thanks for pointing it out.

Burlen

David E DeMarle wrote:
> This is what I was thinking of:
> 	*Parallel Hierarchical Visualization of Large Time-varying 3D Vector 
> Fields*
>
> *Hongfeng Yu, Chaoli Wang, Kwan-Liu Ma
>
> *David E DeMarle
> Kitware, Inc.
> R&D Engineer
> 28 Corporate Drive
> Clifton Park, NY 12065-8662
> Phone: 518-371-3971 x109
>
>
> On Tue, Aug 25, 2009 at 9:46 AM, David E DeMarle 
> <dave.demarle at kitware.com <mailto:dave.demarle at kitware.com>> wrote:
>
>     There was a paper at Super Computing last year (or maybe the year
>     before) about improved partitioning for stream tracing that would
>     probably help alot. Think of making a filter like D3 which moves
>     data around to repartition, such that the partitions take into
>     account the principle flow directions. That way particles stay
>     resident much more often. The upfront cost might be high to do the
>     repartition, but afterwards stream tracing would be faster.
>
>     David E DeMarle
>     Kitware, Inc.
>     R&D Engineer
>     28 Corporate Drive
>     Clifton Park, NY 12065-8662
>     Phone: 518-371-3971 x109
>
>
>     On Tue, Aug 25, 2009 at 4:42 AM, John Biddiscombe
>     <biddisco at cscs.ch <mailto:biddisco at cscs.ch>> wrote:
>
>         Burlen
>
>         I have had performance issues with the Distributed Stream
>         tracer, but in fact I found that in general, the problem of it
>         not being very well optimized for parallel operation was not
>         the main trouble. If you are using Unstructured Grids, and
>         they are large (in my case 20million cells in a block), then
>         the main time was taken by the building of cell links which
>         are used to FindCEll inwhich an integration point lies. I
>         modified the stream tracer interpolation to use a BSP tree (or
>         CellLocator) and found a huge improvement in execution time.
>         (minutes instead of hours).
>
>         Secondly. the parallelization of the stream tracer is an
>         inherent problem. One cannot integrate the streamline in block
>         2, until it has reached a boundary in block 1 - one must wait
>         until the streamling traverses one block before passing it to
>         the next. In actuality, the implementation could be improved
>         with more intelligent seeding and rending/receiving of
>         streamline seeds etc between iterations.
>
>         The Particle tracer code could be modifed to produce
>         streamlines in a serial or distributed manner and ought to
>         give a 'reasonably' optimal solution to the problem - but in
>         fact the chaps at kitware are at the moment (they tell me) in
>         the process of revamping the streamline code to make use of
>         CellLocators - and for this reason I recently committed my BSP
>         tree code.
>
>         Here's how to check your bottleneck.
>         Find a large StructuredGrid dataset which is loaded in
>         parallel. Generate streamlines. Time it. Convert the grdi to
>         UnstructuredGrid and do the same. If test 1 takes 1 minute and
>         test 2 1 hour, then it isn't the parallization that's the real
>         issue, but the grid being used.
>
>         JB
>
>
>
>
>
>             We've been using the distributed stream tracer to generate
>             100s-1000s of stream lines per time step. It's very slow,
>             and it doesn't scale at all.  The class comments say as
>             much. I'm sure there is a reason why this implementation
>             was chosen. Is there something that generally prevents
>             real parallel implementation? Is there a better
>             implementation available out there?
>
>             There is this post a while back
>             http://www.paraview.org/pipermail/paraview/2009-July/012959.html
>
>             What's the status?
>
>             Thanks
>             Burlen
>
>
>
>
>
>
>
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>         -- 
>         John Biddiscombe,                            email:biddisco @
>         cscs.ch <http://cscs.ch>
>         http://www.cscs.ch/
>         CSCS, Swiss National Supercomputing Centre  | Tel:  +41 (91)
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