this is a test harness used to profile and optimize vtkDepthSortPolyData. The main is in ds.cpp and the optimized code is in vtkDepthSortPolyData2.cxx vtkPolyData has been patched.

Timing of the old and new code are shown below. Each of the 3 sorting methods provided have been tested. In the figure, point corresponds to VTK_SORT_FIRST_POINT, bounds corresponds to VTK_SORT_BOUNDS_CENTER, and param corresponds to VTK_SORT_PARAMETRIC_CENTER.

vtkDepthSortPolyData was changed as follows:

• transfrom GetCell to GetCellPoints. Building the cell is expensive and we only need points to determine the depth. We can also then access the points in place.
• transform qsort to std::sort. Comparisons in std::sort get inlined.
• use templates to deal with point types instead of going through virtual GetValue API
• restructure bounds computations so that it can be vectorized by the compiler.
• Allocate the exact amount of memmory for the output and build the output without using virtual API

vtkPolyData was changed as follows:

• inline the non-virtual overload of GetCellPoints.
• avoid virtual API in BuildCells
• add a NeedToBuildCells to check that fast API can safely be used

Test data is in the file iso.vtk. This file contains 10 iso-surfaces generated by ParaView using a 256^3 cosmology simulation. There are 2 scalar fields, 8.1M cells, and 4.1M points. The file is approx 250MB. It is too large to store in github, so I split it into 50M files. The config.sh script will merge them.

I assume you make a directory called bin inside the source and cd into it.

Becasuse some of the optimization require specific compiler flags use the shell script to configure. You might have to change these flags for your system. Use the same flags to build VTK if you desire a fair comparison.

../configure.sh make

Pass a 2 character mode string and input and output file names on the command line. Time to run the depth sort is sent to the stderr. The 2 character mode string is composed of code character and sort character. To select the code use 1 for the old code and 2 for the new. To select the mode use 1 for VTK_SORT_FIRST_POINT, use 2 for VTK_SORT_BOUNDS_CENTER, and 3 for VTK_SORT_PARAMETRIC_CENTER. Use "" for output file name if you want to skip writing the result.

for example: ./ds 12 ../iso.vtk "" ./ds 22 ../iso.vtk "" runs the new and old code using BOUNDS_CENTER sorting.