Hi Stephan,<br><br>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. <br>
<br>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.<br>
<br>Andy<br><br><div class="gmail_quote">On Thu, May 31, 2012 at 4:16 AM, Stephan Rogge <span dir="ltr"><<a href="mailto:Stephan.Rogge@tu-cottbus.de" target="_blank">Stephan.Rogge@tu-cottbus.de</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hello,<br>
<br>
I have a question related to the parallelism of the stream tracer: As I<br>
understand the code right, each line integration (trace) is processed in an<br>
own MPI process. Right?<br>
<br>
To test the scalability of the Stream tracer I've load a structured<br>
(curvilinear) grid and applied the filter with a Seed resolution of 1500 and<br>
check the timings in a single and multi-thread (Multi Core enabled in PV<br>
GUI) situation.<br>
<br>
I was really surprised that multi core slows done the execution time to 4<br>
seconds. The single core takes only 1.2 seconds. Data migration cannot be<br>
the explanation for that behavior (0.5 seconds). What is the problem here?<br>
<br>
Please see attached some statistics...<br>
<br>
Data:<br>
* Structured (Curvilinear) Grid<br>
* 244030 Cells<br>
* 37 MB Memory<br>
<br>
System:<br>
* Intel i7-2600K (4 Cores + HT = 8 Threads)<br>
* 16 GB Ram<br>
* Windows 7 64 Bit<br>
* ParaView (master-branch, 64 bit compilation)<br>
<br>
#################################<br>
Single Thread (Seed resolution 1500):<br>
#################################<br>
<br>
Local Process<br>
Still Render, 0.014 seconds<br>
RenderView::Update, 1.222 seconds<br>
vtkPVView::Update, 1.222 seconds<br>
Execute vtkStreamTracer id: 2184, 1.214 seconds<br>
Still Render, 0.015 seconds<br>
<br>
#################################<br>
Eight Threads (Seed resolution 1500):<br>
#################################<br>
<br>
Local Process<br>
Still Render, 0.029 seconds<br>
RenderView::Update, 4.134 seconds<br>
vtkSMDataDeliveryManager: Deliver Geome, 0.619 seconds<br>
FullRes Data Migration, 0.619 seconds<br>
Still Render, 0.042 seconds<br>
OpenGL Dev Render, 0.01 seconds<br>
<br>
<br>
Render Server, Process 0<br>
RenderView::Update, 4.134 seconds<br>
vtkPVView::Update, 4.132 seconds<br>
Execute vtkStreamTracer id: 2193, 3.941 seconds<br>
FullRes Data Migration, 0.567 seconds<br>
Dataserver gathering to 0, 0.318 seconds<br>
Dataserver sending to client, 0.243 seconds<br>
<br>
Render Server, Process 1<br>
Execute vtkStreamTracer id: 2193, 3.939 seconds<br>
<br>
Render Server, Process 2<br>
Execute vtkStreamTracer id: 2193, 3.938 seconds<br>
<br>
Render Server, Process 3<br>
Execute vtkStreamTracer id: 2193, 4.12 seconds<br>
<br>
Render Server, Process 4<br>
Execute vtkStreamTracer id: 2193, 3.938 seconds<br>
<br>
Render Server, Process 5<br>
Execute vtkStreamTracer id: 2193, 3.939 seconds<br>
<br>
Render Server, Process 6<br>
Execute vtkStreamTracer id: 2193, 3.938 seconds<br>
<br>
Render Server, Process 7<br>
Execute vtkStreamTracer id: 2193, 3.939 seconds<br>
<br>
Cheers,<br>
Stephan<br>
<br>
<br>
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</blockquote></div><br>