[vtkusers] VTK 7.0.0 + Python: GIL released?

[Mathieu Westphal]

Hi

Sorry, I did not see you were only on VTK.
The option is exposed in ParaView cmake option, the same way
VTK_NO_PYTHON_THREAD is.
But you should be able to define the option manually when configuring VTK.

-DVTK_PYTHON_FULL_THREADSAFE:BOOL="ON"

Regards,

Mathieu Westphal

On Thu, Sep 8, 2016 at 2:11 PM, Paul Melis <paul.melis at surfsara.nl> wrote:

> Great! But the VTK_PYTHON_FULL_THREADSAFE option doesn't seem to exist at
> the CMake level. With a git update of a minute ago:
>
> /data/c/vtk-git$ find . -name CMakeLists.txt | xargs -iX grep -Hs
> VTK_PYTHON_FULL_THREADSAFE X
> <empty>
>
> /data/c/vtk-git$ find . | xargs -iX grep -Hs VTK_PYTHON_FULL_THREADSAFE X
> ./Utilities/PythonInterpreter/vtkPythonInterpreter.cxx:#ifdef
> VTK_PYTHON_FULL_THREADSAFE
> ./Utilities/Python/vtkPythonConfigure.h.in:#cmakedefine
> VTK_PYTHON_FULL_THREADSAFE
> ./Utilities/Python/vtkPython.h:// Note: behaviour of this class depends
> on VTK_PYTHON_FULL_THREADSAFE.
> ./Utilities/Python/vtkPython.h: // If force is TRUE, lock/unlock even if
> VTK_PYTHON_FULL_THREADSAFE is not defined.
> ./Utilities/Python/vtkPython.h: // If force is FALSE, lock/unlock is only
> performed if VTK_PYTHON_FULL_THREADSAFE is
> ./Utilities/Python/vtkPython.h:#ifdef VTK_PYTHON_FULL_THREADSAFE
> ./Utilities/Python/vtkPython.h: // Force is always true with
> VTK_PYTHON_FULL_THREADSAFE
>
> /data/c/vtk-git-release$ cmake -DVTK_WRAP_PYTHON=ON ../vtk-git
> ...
> /data/c/vtk-git-release$ grep VTK_PYTHON_FULL_THREADSAFE CMakeCache.txt
> <empty>
>
> /data/c/vtk-git-release$ grep THREAD CMakeCache.txt
> CMAKE_THREAD_LIBS:STRING=-lpthread
> LIBPROJ_USE_THREAD:BOOL=ON
> VTK_MAX_THREADS:STRING=64
> CMAKE_HAVE_PTHREADS_CREATE:INTERNAL=
> CMAKE_HAVE_PTHREAD_CREATE:INTERNAL=1
> CMAKE_HAVE_PTHREAD_H:INTERNAL=1
> //ADVANCED property for variable: CMAKE_THREAD_LIBS
> CMAKE_THREAD_LIBS-ADVANCED:INTERNAL=1
> H5_HAVE_PTHREAD_H:INTERNAL=1
> H5_SYSTEM_SCOPE_THREADS:INTERNAL=1
> HAVE_PTHREAD_H:INTERNAL=1
> //Have symbol PTHREAD_MUTEX_RECURSIVE
> HAVE_PTHREAD_MUTEX_RECURSIVE_DEFN:INTERNAL=
> HDF5_ENABLE_THREADSAFE:INTERNAL=OFF
> //ADVANCED property for variable: LIBPROJ_USE_THREAD
> LIBPROJ_USE_THREAD-ADVANCED:INTERNAL=1
> SYSTEM_SCOPE_THREADS:INTERNAL=TRUE
> //ADVANCED property for variable: VTK_MAX_THREADS
> VTK_MAX_THREADS-ADVANCED:INTERNAL=1
>
> Paul
>
> ------------------------------
> *From: *"Mathieu Westphal" <mathieu.westphal at kitware.com>
> *To: *"Paul Melis" <paul.melis at surfsara.nl>
> *Cc: *"vtk" <vtkusers at vtk.org>
> *Sent: *Thursday, 8 September, 2016 13:51:18
> *Subject: *Re: [vtkusers] VTK 7.0.0 + Python: GIL released?
>
> Hi
>
> All python calls are protected by gil if the VTK_PYTHON_FULL_THREADSAFE
> option is on.
> The mechanism take place in vtkPython.h, where the
> vtkPythonScopeGilEnsurer is configured by the cmake option.
> the vtkPythonScopeGilEnsurer is then ( suposed to be ) used before every
> pthon call.
>
> Regards,
>
> Mathieu Westphal
>
> On Thu, Sep 8, 2016 at 1:23 PM, Paul Melis <paul.melis at surfsara.nl> wrote:
>
>> Hi all,
>>
>> What's the status of threading in VTK 7.0.0 under Python w.r.t the GIL,
>> specifically for classes derived from vtkAlgorithm?
>> I'm attempting to offload a computation (basically
>> vtkStreamTracer.Update())
>> to a Python threading.Thread, but strongly get the impression that
>> the GIL is not released by Update().
>>
>> The release notes (https://blog.kitware.com/vtk-7-0-0/) seem to suggest
>> there was some recent development in this area:
>>
>> * multi-threaded Python codes facilitated by VTK's new and optional
>>   protocol for using the Global Interpreter Lock
>>
>> But clicking the link appears to indicate this is for VTK used inside
>> Paraview only. I see the mentioned cmake variable
>> VTK_PYTHON_FULL_THREADSAFE
>> referenced by files under Utilities/Python, but the cmake files themselves
>> don't contain a reference, nor something like an option. Would hacking
>> the define in somewhere cause Update() to be protected by the GIL?
>> Commit https://github.com/Kitware/VTK/commit/
>> 8eb50dd23fd762d42fe1a6785bbaa704f2ed76c3
>> lists some classes and their possible protection by
>> vtkPythonScopeGilEnsurer,
>> but what specifically is covered isn't entirely clear to me.
>>
>> Thanks,
>> Paul
>>
>> --
>>
>> Paul Melis
>> | Visualization group leader & developer | SURFsara |
>> | Science Park 140 | 1098 XG Amsterdam |
>> | T 020 800 1312 | paul.melis at surfsara.nl | www.surfsara.nl |
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