[vtkusers] vtkImageAppend does not work correctly with multiple threads

[David Gobbi]

Hi Dominik,

Thanks, I just needed confirmation of what you had done to ensure that
the bug was specifically in vtkImageAppend and not in some other
filter in your pipeline.

Thread-related problems in the imaging filters are often due to
incorrect assumptions by the execute methods about how the extents
will be broken up for different threads.  I notice that vtkImageAppend
does not have its own regression test, instead it is tested indirectly
by Imaging/Testing/Tcl/TestAllFlips.tcl and a few others, and only for
2D images.

If you can send a short test for it that crashes, one that can
eventually become part of the nightly testing, that would be the best
way to proceed.

 - David


On Thu, May 26, 2011 at 12:01 PM, Dominik Szczerba <dominik at itis.ethz.ch> wrote:
> Yes, that was my point, it only works correctly with SetNumberOfThreads(1).
> So there seems to be a bug, I am happy to debug and patch,
> unfortunately, the code implementation is hardly documented...
> Any hints are appreciated.
> Dominik
>
> On Thu, May 26, 2011 at 5:58 PM, David Gobbi <david.gobbi at gmail.com> wrote:
>> Hi Dominik,
>>
>> If you call SetNumberOfThreads(1) does it make the problem go away?
>>
>>  - David
>>
>>
>> On Thu, May 26, 2011 at 9:37 AM, Dominik Szczerba <dominik at itis.ethz.ch> wrote:
>>>
>>> I have found that vtkImageAppend only works correctly for me
>>> (preserving extents, overlapping regions) with one thread. With more
>>> it crashes reported incorrect input/output pointers.
>>> Did anybody have similar problems?
>>>
>>> Thanks,
>>> Dominik