[vtkusers] How to use OpenMP with VTK

[Berk Geveci]

For reference: http://www.vtk.org/Wiki/images/3/3b/VTK_SMP_Guide.pdf

This is a work in progress so please feel free to ask questions.

To answer your specific question, GetTuple1() is not thread safe. You
need to use a version of GetTuple() that is thread safe. Like this
one:

  virtual void GetTuple(vtkIdType i, double * tuple);

For this type of work, you will have to make sure that each function
that you use in a parallel section is thread safe by checking out the
implementation. Currently, this is the only way.

Best,
-berk


On Mon, Mar 17, 2014 at 4:59 PM, David E DeMarle
<dave.demarle at kitware.com> wrote:
>
> I recommend you follow the pattern of the filters Filters/SMP (first
> appearing vtk 6.1).
> OpenMP is one of the threading back ends that these filters can use
> efficiently.
>
> David E DeMarle
> Kitware, Inc.
> R&D Engineer
> 21 Corporate Drive
> Clifton Park, NY 12065-8662
> Phone: 518-881-4909
>
>
> On Mon, Mar 17, 2014 at 4:35 PM, Sunrise <helios.corona at gmail.com> wrote:
>>
>> Hello,
>>
>> I would like to parallelize the vtk filter that I wrote using OpenMP, and
>> I just started learning OpenMP on a need basis. A part of code is a for loop
>> over tuples of a vtkDoubleArray. Each tuple is associated with a point on
>> Data. The computation for each point is totally independent and
>> embarrassingly parallelize-able. A short version of part of the code is
>>
>> vtkDoubleArray *InputArray = ... // Get it from Input Data
>> vtkDoubleArray *OutputArray = ... // Define new array
>>
>> #pragma omp parallel for
>> for(int PointId = 0; PointId < InputArray->GetNumberOfTuples(); PointId++)
>> {
>>     double InputValue = InputArray->GetTuple1(PointId);
>>     double OutputValue = DoSomething(InputValue,OtherParameters);
>>     OutputArray->SetTuple1(OutputValue);
>> }
>>
>> However, I am getting the following error for GetTuple1() method:
>>
>> ERROR: In
>> /SomePath/paraview/ParaView-4.1.0-source/VTK/Common/Core/vtkDataArrayTemplate.txx,
>> line 598
>> vtkDoubleArray (0x14bf6808): Unable to allocate 1 elements of size 8
>> bytes.
>>
>> Aborted
>>
>> Could anyone help me to use OpenMP within my filter?
>>
>> Thank you,
>> -Sia
>>
>> _______________________________________________
>> Powered by www.kitware.com
>>
>> Visit other Kitware open-source projects at
>> http://www.kitware.com/opensource/opensource.html
>>
>> Please keep messages on-topic and check the VTK FAQ at:
>> http://www.vtk.org/Wiki/VTK_FAQ
>>
>> Follow this link to subscribe/unsubscribe:
>> http://www.vtk.org/mailman/listinfo/vtkusers
>>
>
>
> _______________________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
>
> Please keep messages on-topic and check the VTK FAQ at:
> http://www.vtk.org/Wiki/VTK_FAQ
>
> Follow this link to subscribe/unsubscribe:
> http://www.vtk.org/mailman/listinfo/vtkusers
>