[vtk-developers] vtkDepthSortPolyData modernization

[Burlen Loring]

Hi Will,

Your recent post mentioning changing std::sort to vtkSMPTools::Sort() 
had me thinking about that, and also about giving the gift of code. In 
the algorithm there are 3 distinct parts, computing the depths, sorting, 
and building the output. Each of of those could be parallelized. I'm 
willing to try it. Thanks for the suggestion!

Burlen

On 11/12/2015 10:20 AM, Will Schroeder wrote:
> Burlen I would use vtkSMPTools::Sort(). Under the hood it uses 
> std::sort when VTK is built in VTK_SMP_IMPLEMENTATION_TYPE=Sequential 
> mode (default). But when built with VTK_SMP_IMPLEMENTATION_TYPE=TBB, 
> etc. you'll see significant parallelization benefits.
>
> W
>
> On Wed, Nov 11, 2015 at 12:04 PM, Burlen Loring 
> <burlen.loring at gmail.com <mailto:burlen.loring at gmail.com>> wrote:
>
>     Hi All,
>
>     Would anyone be willing to review this patch?
>     https://gitlab.kitware.com/vtk/vtk/merge_requests/844
>
>     I was profiling VisIt and noticed that vtkDepthSortPolyData (in
>     spite of its limitations it is used by VisIt for transparent
>     rendering) made use of qsort and about 1/2 the time was spent by
>     qsort. std::sort is known to be faster because of the possibility
>     of the compiler to inline the comparisons. Updating qsort to
>     std::sort seemed like an easy way to make it faster. As I worked
>     the profiler pointed out a number of other fairly easy things to
>     improve and overall the class is now ~3x faster for two of the
>     modes and ~2x faster for the other. I enumerated the changes in
>     the commit message and have added a cxx test to improve the test
>     coverage.
>
>     If you have the time, please take a look, and let me know if you
>     have any feedback on it.
>
>     Thanks
>     Burlen
>
>
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> -- 
> William J. Schroeder, PhD
> Kitware, Inc.
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