[Paraview] Parallel Streamtracer

[Andy Bauer]

Hi Stephan,

The parallel stream tracer uses the partitioning of the grid to determine
which process does the integration. When the streamline exits the subdomain
of a process there is a search to see if it enters a subdomain assigned to
any other processes before figuring it whether it has left the entire
domain.

Leo, copied here, has been improving the streamline implementation inside
of VTK so you may want to get his newer version. It is a pretty tough
algorithm to parallelize efficiently without making any assumptions on the
flow or partitioning.

Andy

On Thu, May 31, 2012 at 4:16 AM, Stephan Rogge
<Stephan.Rogge at tu-cottbus.de>wrote:

> Hello,
>
> I have a question related to the parallelism of the stream tracer: As I
> understand the code right, each line integration (trace) is processed in an
> own MPI process. Right?
>
> To test the scalability of the Stream tracer I've load a structured
> (curvilinear) grid and applied the filter with a Seed resolution of 1500
> and
> check the timings in a single and multi-thread (Multi Core enabled in PV
> GUI) situation.
>
> I was really surprised that multi core slows done the execution time to 4
> seconds. The single core takes only 1.2 seconds. Data migration cannot be
> the explanation for that behavior (0.5 seconds). What is the problem here?
>
> Please see attached some statistics...
>
> Data:
> * Structured (Curvilinear) Grid
> * 244030 Cells
> * 37 MB Memory
>
> System:
> * Intel i7-2600K (4 Cores + HT = 8 Threads)
> * 16 GB Ram
> * Windows 7 64 Bit
> * ParaView (master-branch, 64 bit compilation)
>
> #################################
> Single Thread (Seed resolution 1500):
> #################################
>
> Local Process
> Still Render,  0.014 seconds
> RenderView::Update,  1.222 seconds
>    vtkPVView::Update,  1.222 seconds
>        Execute vtkStreamTracer id: 2184,  1.214 seconds
> Still Render,  0.015 seconds
>
> #################################
> Eight Threads (Seed resolution 1500):
> #################################
>
> Local Process
> Still Render,  0.029 seconds
> RenderView::Update,  4.134 seconds
> vtkSMDataDeliveryManager: Deliver Geome,  0.619 seconds
>    FullRes Data Migration,  0.619 seconds
> Still Render,  0.042 seconds
>    OpenGL Dev Render,  0.01 seconds
>
>
> Render Server, Process 0
> RenderView::Update,  4.134 seconds
>    vtkPVView::Update,  4.132 seconds
>        Execute vtkStreamTracer id: 2193,  3.941 seconds
> FullRes Data Migration,  0.567 seconds
>    Dataserver gathering to 0,  0.318 seconds
>    Dataserver sending to client,  0.243 seconds
>
> Render Server, Process 1
> Execute vtkStreamTracer id: 2193,  3.939 seconds
>
> Render Server, Process 2
> Execute vtkStreamTracer id: 2193,  3.938 seconds
>
> Render Server, Process 3
> Execute vtkStreamTracer id: 2193,  4.12 seconds
>
> Render Server, Process 4
> Execute vtkStreamTracer id: 2193,  3.938 seconds
>
> Render Server, Process 5
> Execute vtkStreamTracer id: 2193,  3.939 seconds
>
> Render Server, Process 6
> Execute vtkStreamTracer id: 2193,  3.938 seconds
>
> Render Server, Process 7
> Execute vtkStreamTracer id: 2193,  3.939 seconds
>
> Cheers,
> Stephan
>
>
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