[vtkusers] VTK in a multi-threaded program

[Richard Whitehead]

Thanks Berk,
I had no idea this work was in progress, it looks like you are going to
solve the problem for me!!!   From the sound of it, you will not be
introducing threads and triggers into VTK, that will still be an
application domain issue, if I understand correctly?
Please could you explain the couple of lines of code you included, I'm
afraid I don't understand what the objects are or why you seem to refer to
"output" twice in different ways?
Are there any time-scales on when this work might reach a released build?
 I'm working on a medical application and I am very reluctant to use an
unstable build, but will do if I have to, the reward in this case would be
significant.
Huge thanks,
Richard


On 24 March 2014 15:14, Berk Geveci <berk.geveci at kitware.com> wrote:

> Let me add my 2 cents.
>
> First of all, make sure that you are using the latest VTK from Git. It
> makes reference count management thread safe. As long as the reference does
> not go to 0 while another thread is using an object, it will be fine. Using
> smart pointers will also be OK. Git VTK has bunch of other thread safety
> improvements by the way.
>
> Second, when you hand data from the compute thread to the render thread, I
> would use a shallow copy. Something like:
>
> copyToRender = output->NewInstance();
> copyToRender->ShallowCopy(output);
>
> Make sure that this is protected by a mutex if the compute thread
> eventually deletes "output". This would not be needed normally but there is
> still some garbage collection left that may cause issues. This should make
> it safe. It will be unnecessary in the future as we clean things more.
>
> Finally, never connect a pipeline across threads. Render should cause
> filters that belong to another to execute.
>
> If you are still running into specific thread safety issue, try to trace
> them with helgrind and please report them to this list or to me directly.
>
> Best,
> -berk
>
>
>
>
>
> On Mon, Mar 24, 2014 at 11:00 AM, Aashish Chaudhary <
> aashish.chaudhary at kitware.com> wrote:
>
>> On Mon, Mar 24, 2014 at 10:53 AM, David Cole <dlrdave at aol.com> wrote:
>>
>>> Hi Aashish,
>>>
>>> The blog post you pointed to was published in October 2012, and
>>> referenced releasing the source code by the end of 2013. Was the source
>>> code released? Is there a public repo for it?
>>>
>>
>> At the end of the blog, Rusty answered this question. Please have a look
>> at it.
>>
>>>
>>> I find it hard to believe that the only thing you had to do was "a
>>> vtkSmartPointer trick"...
>>>
>>
>> It was not just that but it was part of the core implementation.
>>
>>>
>>> If there is a way to run, for example, the vtkMarchingCubes filter on a
>>> large volumetric dataset, with a pipeline that's in a background non-GUI
>>> thread, it sure would be useful to have a snippet of example code that
>>> proves it. Or any other long running vtkAlgorithm, for that matter.
>>>
>>
>> I don't remember what algorithms we ran but they were mostly image based
>> or our own written in VTK.
>>
>> - Aashish
>>
>>>
>>>
>>> Thanks,
>>> David
>>>
>>>
>>
>>
>> --
>> | Aashish Chaudhary
>> | R&D Engineer
>> | Kitware Inc.
>> | www.kitware.com
>>
>> _______________________________________________
>> 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
>>
>>
>


-- 

Richard Whitehead *-* Senior Imaging Engineer

*Michelson Diagnostics Ltd*

*M:* +44 (0)7905 955276   *T:* +44 (0)20 8308 1695

*E: *richard.whitehead at vivosight.com   *W:* www.vivosight.com


<http://www.vivosight.com/>


Michelson Diagnostics Ltd, 1 Grays Farm Production Village, Grays Farm
Road, Orpington, Kent  BR5 3BD, UK

Registered Office: 3 Shearwater, Maidstone, ME16 0DW.     Registered in
England No. 5732681
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.vtk.org/pipermail/vtkusers/attachments/20140324/69c6ec07/attachment.html>