[Paraview-developers] VTK_NO_PYTHON vs VTK_PYTHON_FULL_THREADSAFE

[Chris Harris]

Hi Mathieu,

Thanks for explanation ( yes VTK_NO_PYTHON was a typo :-( )

Chris

On Fri, Sep 2, 2016 at 2:44 AM, Mathieu Westphal <
mathieu.westphal at kitware.com> wrote:

> Hello
>
> you may have noticed, the option is not VTK_NO_PYTHON, but
> VTK_NO_PYTHON_THREAD
>
> When this option is true, all python threading is disabled, and all python
> related method are executed in one and only thread, no python thread
> support.
> If this option is false, a new option appear, VTK_PYTHON_FULL_THREADSAFE.
>
> VTK_NO_PYTHON_THREAD false and VTK_PYTHON_FULL_THREADSAFE false is
> basically the standard way to compile VTK with python.
>
> If you pass VTK_PYTHON_FULL_THREADSAFE to true, then each and every call
> to python will be protected with GIL [1], ensuring that you can have eg.
> other python interpreter in your application
> and still use python wrapping in vtk. Very usefull option for specific
> usage but quite an overhead for people that have no use for it and only use
> python inside VTK.
>
> on a side note, The logic in vtkPython.h is quite complicated because even
> without VTK_PYTHON_FULL_THREADSAFE, we sometimes needs to protect the
> python call with gil anyway, hence the "FULL" in the option name.
>
> I hope it is more clear now.
> Regards,
>
> Mathieu Westphal
>
> [1] : https://en.wikipedia.org/wiki/Global_interpreter_lock
>
> Mathieu Westphal
>
> On Thu, Sep 1, 2016 at 5:58 PM, Chris Harris <chris.harris at kitware.com>
> wrote:
>
>> Can someone clear up what these two CMake options are for? It seems the
>> ParaView has VTK_PYTHON_FULL_THREADSAFE as a dependant option that can only
>> be enable if VTK_NO_PYTHON is off.
>>
>> I am asking because I would like to know which should be used to
>> selectively compile GIL locks and releases.
>>
>> It seems that VTK_NO_PYTHON is used here:
>>
>> https://github.com/Kitware/VTK/blob/master/Utilities/Python/
>> vtkPython.h#L107-L112
>>
>> and
>>
>> VTK_PYTHON_FULL_THREADSAFE is used here:
>>
>> https://github.com/Kitware/VTK/blob/master/Utilities/Python/
>> vtkPython.h#L131-L134
>>
>>
>> It seems the VTK_PYTHON_FULL_THREADSAFE was added relatively recently.
>>
>> Thanks,
>>
>>
>> Chris
>>
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