[Bf-committers] OpenMP issues with msvc2013 builds

[Martijn Berger]

Excellent plan Bastien.
>From a semantic standpoint combining different threading strategies and or
support libraries within one project is really far from ideal.
For this to work we would need to write some kind of document or declare
some already implemented part of code "the official way" to do this.

Yes the code would be more verbose compared to openmp but also more
explicit and likely better to control versus the current zoo of tricks in
order to exploit parallelism.




On Wed, Aug 6, 2014 at 2:15 PM, Bastien Montagne <montagne29 at wanadoo.fr>
wrote:

> We could also choose to drop OMP in our code (not all at once, but
> gradually replacing it with real threading), since it’s also a pile of
> crap on OSX currently afaik?
>
> Assuming our BLI_task 'lib' is ready for massive use (iirc Martijn
> already had that in mind)…
>
> Or is there some serious issues with this approach (aside the slightly
> more verbose [complicated?] code)?
>
> Le 06/08/2014 13:26, Sergey Sharybin a écrit :
> > Switching to icc wouldn't happen any time soon anyway, so afraid we'll
> need
> > to have some shorter-term solution anyway... The question only is what
> > exactly we'll choose.
> >
> > P.S. And yeah, there's nothing more permanent as a temporary solution..
> >
> >
> > On Wed, Aug 6, 2014 at 4:48 PM, Martijn Berger <martijn.berger at gmail.com
> >
> > wrote:
> >
> >> Hi Campbell,
> >>
> >> I last compiled with intel c++ a few month's ago and without OSL /
> Collada.
> >> In general it works but as with any change it will again probably expose
> >> lots of little issues once people actually use builds intensively.
> >>
> >> Main issue is the compiler is not free to use for windows not even for
> open
> >> source projects. ( the linux toolchain is free for open source ).
> >>
> >>
> >>
> >> On Wed, Aug 6, 2014 at 12:43 PM, Campbell Barton <ideasman42 at gmail.com>
> >> wrote:
> >>
> >>> On Wed, Aug 6, 2014 at 6:23 PM, Sergey Sharybin <sergey.vfx at gmail.com>
> >>> wrote:
> >>>> Hi,
> >>>>
> >>>> We've spent quite a while trying to solve the upcoming stream of
> >> reports
> >>>> about high CPU usage with builds made with msvs2013 in certain
> >>> situations.
> >>>> Root of the issue goes to the change made to OMP inplementation back
> to
> >>>> msvc2010 days -- they've forced threads to spin for a while after they
> >>> did
> >>>> a work. This is a know issue in the library and nobody actually gonna
> >> to
> >>>> fix it [1].
> >>>>
> >>>> There's one woekaround to solve the issue which is to set
> >> OMP_WAIT_POLICY
> >>>> environment variable to PASSIVE. Unfortunately, since openmp is a
> >> dynamic
> >>>> library and can't be linked statically at all we can't modify
> >> environment
> >>>> variables from within blender using putenv(), this is to be done
> >>>> externally, before blender.exe starts.
> >>>>
> >>>> Here's the list of possible solutions:
> >>>>
> >>>> - Declare msvc full of crap, switch to intel compilers
> >>> Did anyone try Intel-c/c++ on Windows?
> >>>
> >>> A while back I got Blender building on Linux with Intel's compiler, it
> >>> needed a few tweaks in CMake but wasn't really a big deal to get
> >>> running.
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> >
> >
>
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