[vtk-developers] VTK6 performance issue wrt VTK5

[Julien Finet]

Hi,

I have noticed a decrease in performance when switching from VTK5 to VTK6.
This is related to the number of actors in the scene and the pipeline
updates.

Here I use VTK Rendering TimeRenderer test to compare the 2 versions. To
average the timing, the render loop has been increased from 360 to 3600
iterations. Here are some results:
 VTK 5: 100 actors: 13.5s
 VTK 6: 100 actors: 13.5s (100%)
 VTK 5: 300 actors: 13.1s
 VTK 6: 300 actors: 15.6s (115%)
 VTK 5: 600 actors: 13.1s
 VTK 6: 600 actors: 21.3s (163%)
 VTK 5: 1000 actors: 15.1s
 VTK 6: 1000 actors: 33.5s (222%)

A simpler test that only calls GetBounds() multiple times on a
vtkPolyDataMapper produces the following time-ordered-backtraces:
VTK 5:
Running Time Self Symbol Name
221.5ms  100.0% 0.6  vtkPolyDataMapper::GetBounds()
122.0ms   55.0% 0.6  vtkStreamingDemandDrivenPipeline::Update(int)
090.0ms   40.6% 0.4   vtkDemandDrivenPipeline::UpdateInformation()
019.3ms    8.7% 1.0
vtkStreamingDemandDrivenPipeline::PropagateUpdateExtent(int)
009.6ms    4.3% 1.0
vtkStreamingDemandDrivenPipeline::ProcessRequest(vtkInformation*,
vtkInformationVector**, vtkInformationVector*)
001.0ms    0.4% 1.0   vtkExecutive::CheckAlgorithm(char const*,
vtkInformation*)
000.4ms    0.1% 0.0   vtkDemandDrivenPipeline::UpdateData(int)
000.2ms    0.0% 0.2   vtkAlgorithm::GetNumberOfOutputPorts()
000.2ms    0.0% 0.2   vtkInformationIntegerKey::Set(vtkInformation*, int)
000.2ms    0.0% 0.2   vtkInformation::Has(vtkInformationRequestKey*)
000.1ms    0.0% 0.1   vtkInformationRequestKey::Has(vtkInformation*)
000.1ms    0.0% 0.1   vtkExecutive::GetOutputInformation()
000.1ms    0.0% 0.1
vtkStreamingDemandDrivenPipeline::REQUEST_UPDATE_EXTENT()
000.0ms    0.0% 0.0   vtkExecutiveInternals::GetInputInformation(int)
000.0ms    0.0% 0.0   vtkDemandDrivenPipeline::UpdateDataObject()
000.0ms    0.0% 0.0   vtkDemandDrivenPipeline::ProcessRequest(vtkInformation*,
vtkInformationVector**, vtkInformationVector*)
000.0ms    0.0% 0.0   vtkDemandDrivenPipeline::REQUEST_DATA()
064.2ms   28.9% 1.7  vtkPolyDataMapper::Update()
027.5ms   12.4% 1.1  vtkPainterPolyDataMapper::ComputeBounds()
002.1ms    0.9% 0.0  vtkExecutive::GetNumberOfInputConnections(int)
000.8ms    0.3% 0.8  vtkClipPlanesPainter::UpdateBounds(double*)
000.7ms    0.3% 0.7  vtkPainter::GetDelegatePainter()
000.6ms    0.2% 0.6  vtkDataObject::SetUpdateExtent(int, int, int)
000.5ms    0.2% 0.4  vtkPainter::UpdateBounds(double*)

VTK 6:
Running Time Self Symbol Name
1077.5ms  100.0% 2.6  vtkPolyDataMapper::GetBounds()
846.6ms   78.5% 0.7  vtkStreamingDemandDrivenPipeline::Update(int)
335.7ms   31.1% 2.0   vtkStreamingDemandDrivenPipeline::PropagateTime(int)
298.3ms   27.6% 1.3
vtkStreamingDemandDrivenPipeline::UpdateTimeDependentInformation(int)
123.8ms   11.4% 1.4
vtkStreamingDemandDrivenPipeline::PropagateUpdateExtent(int)
068.4ms    6.3% 0.4   vtkDemandDrivenPipeline::UpdateInformation()
009.2ms    0.8% 1.6
vtkStreamingDemandDrivenPipeline::ProcessRequest(vtkInformation*,
vtkInformationVector**, vtkInformationVector*)
000.6ms    0.0% 0.6   vtkInformationIntegerKey::Set(vtkInformation*, int)
000.5ms    0.0% 0.5   vtkExecutive::GetOutputInformation()
000.4ms    0.0% 0.4   vtkInformation::Set(vtkInformationRequestKey*)
000.4ms    0.0% 0.4   vtkInformationRequestKey::Set(vtkInformation*)
000.3ms    0.0% 0.0   vtkDemandDrivenPipeline::UpdateData(int)
000.3ms    0.0% 0.3   vtkInformation::Set(vtkInformationIntegerKey*, int)
000.3ms    0.0% 0.3   vtkAlgorithm::GetNumberOfOutputPorts()
000.2ms    0.0% 0.2   vtkInformation::Has(vtkInformationRequestKey*)
000.2ms    0.0% 0.2   vtkExecutiveInternals::GetInputInformation(int)
000.1ms    0.0% 0.1   vtkExecutive::CheckAlgorithm(char const*,
vtkInformation*)
000.1ms    0.0% 0.1   vtkDemandDrivenPipeline::UpdateDataObject()
000.1ms    0.0% 0.1   vtkDemandDrivenPipeline::ProcessRequest(vtkInformation*,
vtkInformationVector**, vtkInformationVector*)
000.1ms    0.0% 0.1   vtkInformationRequestKey::Has(vtkInformation*)
000.0ms    0.0% 0.0   vtkExecutive::GetInputInformation()
0080.8ms    7.4% 0.8   vtkDemandDrivenPipeline::UpdateInformation()
0048.6ms    4.5% 1.2  vtkPainterPolyDataMapper::ComputeBounds()
0030.5ms    2.8% 1.9
vtkStreamingDemandDrivenPipeline::SetUpdateExtent(vtkInformation*,
int, int, int)
0021.7ms    2.0% 0.6  vtkAlgorithm::GetInputAlgorithm(int, int)
0010.3ms    0.9% 2.2
vtkStreamingDemandDrivenPipeline::ProcessRequest(vtkInformation*,
vtkInformationVector**, vtkInformationVector*)
007.5ms    0.6% 4.1  vtkPainter::UpdateBounds(double*)
005.8ms    0.5% 1.2  vtkAlgorithm::GetInputInformation(int, int)
005.2ms    0.4% 0.9  vtkAlgorithm::UpdateInformation()
002.4ms    0.2% 0.1  vtkExecutive::GetNumberOfInputConnections(int)


Calling SetStatic() on all the mappers improve things:
 VTK 5: 100 actors: 6.7s
 VTK 6: 100 actors: 6.7s (100%)
 VTK 5: 1000 actors: 6.7s
 VTK 6: 1000 actors: 8.4s (125%)
While the performance is still hit, it is more acceptable. However, for my
use case, making my mappers static is not an option.

A hack to disable the time propagation also improve things a bit:
 VTK 5: 100 actors: 6.7s
 VTK 6: 100 actors: 6.7s (100%)
 VTK 5: 1000 actors: 15.1s
 VTK 6: 1000 actors: 20.0s (132%)
While time propagation is responsible for a large part of the slowness, it
still does not explain 100% of the performance decrease.

Any suggestion ?
As a quick fix, we could improve the "Static" property of the mappers by
specifying if the mapper input is "time static" (e.g.
vtkMapper::SetStatic(2) or vtkMapper::SetTimeStatic(1)).

Thanks,
Julien.
p.s. TimeRenderer currently segfaults in VTK6 trunk due to a missing
auto-initialization.
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