[vtk-developers] Checking SMP backend at runtime/compiletime?

[Ken Martin]

Echoing David's earlier comments it would seem like we would want a nice
path to convert existing multithreaded algorithms to use vtkSMPTools
knowing that vtkSMPTools would not slow down the existing algorithm. Doing

#if VTK_SMP_BACKEND == SLOW
 use vtkMultithreader
#else
  use vtkSMPTools
#endif

sounds odd. I did not read the pdf so if that is covered in there apologies.




On Tue, Feb 9, 2016 at 10:56 AM, David Gobbi <david.gobbi at gmail.com> wrote:

> Hi Sujin,
>
> That sounds good.  Even if the choice of backend is transparent as far as
> using vtkSMPTools is concerned, it's very nice to be able to report which
> backend was configured.
>
>  - David
>
> On Tue, Feb 9, 2016 at 8:46 AM, Sujin Philip <sujin.philip at kitware.com>
> wrote:
>
>> Hi Sean,
>>
>> vtkSMPTools is a framework for implementing multi-threaded algorithms in
>> VTK. It support several backends. The main ones are TBB and OpenMP. There
>> are Kaapi and Simple backends which are no longer supported and will be
>> removed soon. Finally, the default backend is Sequential which is just a
>> single threaded implementation of the framework. After removal of the Kaapi
>> and Simple backend, if you need multithreading support on Clang you would
>> have to use TBB. The Sequential backend will be supported on all platforms.
>>
>> David,
>>
>> I have talked with Berk about this and I will soon make a change to have
>> a compile time macro to check for SMP backend type. I will also finally
>> remove Kaapi and Simple backend as part of this change.
>>
>> Thanks
>> Sujin
>>
>>
>> On Tue, Feb 9, 2016 at 10:28 AM, Sean McBride <sean at rogue-research.com>
>> wrote:
>>
>>> On Tue, 9 Feb 2016 09:13:48 -0500, Sujin Philip said:
>>>
>>> >Why would you want to continue using vtkMultiThreader when Sequential or
>>> >Simple is used? In fact, now that there is an openmp backend, we should
>>> be
>>> >removing simple. It was only there to ease debugging since tbb had very
>>> >complex back-traces. Openmp back-traces are much more readable. Do you
>>> want
>>> >the algorithm to be multithreaded even when Sequential is used?
>>>
>>> I don't know the APIs you're discussing, so this comment is coming
>>> mostly from ignorance, but: are you talking about requiring OpenMP to build
>>> VTK?  Clang has only very recently added OpenMP support, and IIRC it's not
>>> complete.  Also, last I checked, Apple's fork of clang doesn't support it
>>> at all.
>>>
>>> Cheers,
>>>
>>> --
>>> ____________________________________________________________
>>> Sean McBride, B. Eng                 sean at rogue-research.com
>>> Rogue Research                        www.rogue-research.com
>>> Mac Software Developer              Montréal, Québec, Canada
>>>
>>>
>>>
>>
>
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-- 
Ken Martin PhD
Chairman & CFO
Kitware Inc.
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