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IDProjectCategoryView StatusLast Update
0032851CommunityOCCT:Foundation Classespublic2022-03-29 16:48
Reportersmason Assigned Toabv  
Status newResolutionopen 
PlatformLinuxOSDebian 6.0 
Product Version7.5.3 
Summary0032851: OCCT algorithms create/destroy a large number of threads when Intel TBB enabled
DescriptionI've been using OCCT as a library to validate CAD geometries. I want to manage parallelism myself as I'm doing a lot of small operations with the pave filler and associated BOPs. When running my program under GDB I noticed a lot of threads being created, e.g. lines like:

  [New Thread 0x7fffee5b7640 (LWP 17248)]
  [New Thread 0x7fffed5b3640 (LWP 17249)]
  [New Thread 0x7fffec871640 (LWP 17250)]
  [New Thread 0x7fffed1b2640 (LWP 17252)]
  [New Thread 0x7fffed9b4640 (LWP 17253)]
  [New Thread 0x7fffef25f640 (LWP 17251)]
  [New Thread 0x7fffee1b6640 (LWP 17254)]
  [Thread 0x7fffee1b6640 (LWP 17254) exited]
  [Thread 0x7fffed9b4640 (LWP 17253) exited]
  [Thread 0x7fffef25f640 (LWP 17251) exited]
  [Thread 0x7fffec871640 (LWP 17250) exited]
  [Thread 0x7fffed5b3640 (LWP 17249) exited]
  [Thread 0x7fffee5b7640 (LWP 17248) exited]
  [Thread 0x7fffed1b2640 (LWP 17252) exited]

being printed out, every time BOPAlgo_PaveFiller is performed.
Steps To ReproduceRun with a version of OCCT compiled with Intel TBB enabled, e.g. OCCT as included in Ubuntu 21.10 is compiled like this. Then run:

  BOPAlgo_PaveFiller filler;

I can work around this issue by forcing the use of OCCT's built in thread pool, by calling:


during program initialization, but this feels like a bug.

The following looks like a useful part of the stack trace:

0000007 0x00007ffff7e5c1fc in void tbb::parallel_for_each<OSD_Parallel::UniversalIterator, OSD_Parallel::FunctorInterface>(OSD_Parallel::UniversalIterator, OSD_Parallel::UniversalIterator, OSD_Parallel::FunctorInterface const&) () from /lib/x86_64-linux-gnu/
0000008 0x00007ffff7e5b7f3 in OSD_Parallel::forEachExternal(OSD_Parallel::UniversalIterator&, OSD_Parallel::UniversalIterator&, OSD_Parallel::FunctorInterface const&, int) () from /lib/x86_64-linux-gnu/
0000009 0x00007ffff585c4e1 in void OSD_Parallel::For<GeomLib_CheckCurveOnSurface_Local>(int, int, GeomLib_CheckCurveOnSurface_Local const&, bool) () from /lib/x86_64-linux-gnu/
#10 0x00007ffff585a15c in GeomLib_CheckCurveOnSurface::Perform(opencascade::handle<Geom2d_Curve> const&, bool) () from /lib/x86_64-linux-gnu/
0000011 0x00007ffff7c4e10d in IntTools_Tools::ComputeTolerance(opencascade::handle<Geom_Curve> const&, opencascade::handle<Geom2d_Curve> const&, opencascade::handle<Geom_Surface> const&, double, double, double&, double&, double) () from /lib/x86_64-linux-gnu/
#12 0x00007ffff7c35aaa in IntTools_FaceFace::ComputeTolReached3d() ()
   from /lib/x86_64-linux-gnu/
0000013 0x00007ffff7c3e576 in IntTools_FaceFace::Perform(TopoDS_Face const&, TopoDS_Face const&) ()
   from /lib/x86_64-linux-gnu/
0000014 0x00007ffff7d0ff02 in BOPAlgo_FaceFace::Perform() () from /lib/x86_64-linux-gnu/
0000015 0x00007ffff7d10227 in void OSD_Parallel::For<BOPTools_Parallel::Functor<NCollection_Vector<BOPAlgo_FaceFace> > >(int, int, BOPTools_Parallel::Functor<NCollection_Vector<BOPAlgo_FaceFace> > const&, bool) ()
   from /lib/x86_64-linux-gnu/
0000016 0x00007ffff7d002b2 in BOPAlgo_PaveFiller::PerformFF() () from /lib/x86_64-linux-gnu/
0000017 0x00007ffff7cdd25f in BOPAlgo_PaveFiller::PerformInternal() () from /lib/x86_64-linux-gnu/
0000018 0x00007ffff7cddc6c in BOPAlgo_PaveFiller::Perform() () from /lib/x86_64-linux-gnu/
TagsNo tags attached.
Test case number

Attached Files

  • demo.cpp (1,247 bytes)
  • demo.brep (158,951 bytes)


related to 0030573 closedapn Open CASCADE OSD_Parallel_TBB: limit number of execution threads using settings of OSD_ThreadPool::DefaultPool() 
related to 0032891 newazv Open CASCADE Coding Rules - eliminating TBB deprecation warning on Ubuntu 20.04 



2022-02-21 21:20

developer   ~0107016

The only thing I could imagine to alter TBB behavior is
> tbb::task_scheduler_init aScheduler (aNbThreads);

within src/OSD/OSD_Parallel_TBB.cxx.

If commenting these lines doesn't change behavior - than this threads spawning is by TBB design.


2022-02-21 21:32

reporter   ~0107017

I noticed after posting that I should have written that I have to use:


(but can't see how to edit the issue)

@kgv, yes that call to task_scheduler_init() looked suspicious to me, i.e. is it causing thread pool to be reinitialized every time.

This Ubuntu box isn't my main dev machine (i.e. I don't normally have TBB headers installed) so haven't tried changing that line.


2022-02-22 12:00

developer   ~0107022

@smason, fill free to share your updates when you'll have a time.


2022-03-02 22:43

reporter   ~0107148

Sorry for the delay, it's been a bit of a struggle to reproduce because some defaults seem to have changed and it took a bit to track down what it was. I don't think I'll be affected by this bug in more recent versions of OCCT, as I explicitly disable parallel mode in the pave filler. The version currently bundled with Ubuntu (i.e. 7.5.1) apparently spawns/kills these threads independently of the parallel mode setting.

That said, for users that choose to turn it on I can confirm that removing that line causes a multitude of thread spawns/joins to stop so still seems like something that's worth fixing. I'll let you decide on what that fix is!

I'm including some cut-down C++ code, and a brep file that triggers this for me. I don't think the file is particularly special though, it's mostly default output of paramak (
demo.cpp (1,247 bytes)
demo.brep (158,951 bytes)


2022-03-02 22:48

reporter   ~0107149

oops, forgot to note I'm testing with commit e61aa824dbdbe2cdbdf3606827c136f3f70de90f which still appears to be HEAD of the master branch

am happy to try with something else now I've figured out what's going on

Issue History

Date Modified Username Field Change
2022-02-21 21:12 smason New Issue
2022-02-21 21:12 smason Assigned To => abv
2022-02-21 21:18 kgv Relationship added related to 0030573
2022-02-21 21:20 kgv Note Added: 0107016
2022-02-21 21:32 smason Note Added: 0107017
2022-02-22 12:00 kgv Note Added: 0107022
2022-03-02 22:43 smason Note Added: 0107148
2022-03-02 22:43 smason File Added: demo.cpp
2022-03-02 22:43 smason File Added: demo.brep
2022-03-02 22:48 smason Note Added: 0107149
2022-03-29 16:48 kgv Relationship added related to 0032891