[vtkusers] VTK in a multi-threaded program

[Berk Geveci]

Correction:

Render in one thread should _not_ cause filters that belong to another
thread to execute.

Best,
-berk



On Mon, Mar 24, 2014 at 11:14 AM, 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
>>
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