[Opensg-users] OpenSG Warning Message

[Благоја Стојкоски]

Hi guys,

I'm new to OpenSG, but I started working on a code base that was recently
ported from OpenSG 1.x (I think 1.8, but I'm not sure) to the latest code
from the repo (2.0).

After the port was done, we started getting this Warning message, about 25
times per frame:

WARNING: Unsafe change from multiple threads for FieldContainer
[PassiveWindow]:


Now, the scenario that I have is, I have 4 threads whose changes get merged
like so:


OSG::Thread::getCurrentChangeList()->merge(*my_threads[i]->getChangeList());

This is done in a for cycle that goes through all the threads. my_threads
is an array of OSG::ThreadRefPtr

After this the changes in the threads get cleared with this call:

my_threads[i]->getChangeList()->clear();

This is where the warning message appears. It gets generated in the
FieldContainer.cpp file in line 322 (
http://sourceforge.net/p/opensg/code/ci/master/tree/Source/Base/FieldContainer/Base/OSGFieldContainer.cpp#l322
)

I managed to "fix" this by changing the clearing of the ChangeList to:

my_threads[i]->getCurrentChangeList()->clear();

However, I cannot find what is the difference between getChangeList and
getCurrentChangeList, so I can not be sure if what I did is correct. When
testing the program with this change in place, I can not spot anything
wrong, but I just want to be sure.

That's why I decided to ask you guys. Also I would like to ask you if you
could point me to some other sources of documentation or tutorials for the
latest OpenSG, apart from the wiki on http://www.opensg.org/ and the
documentation on http://opensg.fraunhofer.sg?

Thanks,
Blagoja Stojkoski

[Carsten Neumann]

Hello,

Post by Благоја Стојкоски
Now, the scenario that I have is, I have 4 threads whose changes get
OSG::Thread::getCurrentChangeList()->merge(*my_threads[i]->getChangeList());
This is done in a for cycle that goes through all the threads.
my_threads is an array of OSG::ThreadRefPtr
my_threads[i]->getChangeList()->clear();
This is where the warning message appears. It gets generated in the
FieldContainer.cpp file in line 322
(http://sourceforge.net/p/opensg/code/ci/master/tree/Source/Base/FieldContainer/Base/OSGFieldContainer.cpp#l322)
my_threads[i]->getCurrentChangeList()->clear();
However, I cannot find what is the difference between getChangeList and
getCurrentChangeList, so I can not be sure if what I did is correct.
When testing the program with this change in place, I can not spot
anything wrong, but I just want to be sure.

I doubt this does what you want it to do: Thread::getCurrentChangeList()
is a static member function that returns the ChangeList (CL) of the
thread executing the code, while getChangeList is a (non-static) member
function that returns the CL of the thread object it is called on. So
after the change you are only clearing the current threads CL, not those
you've merged from.

The message warns that multiple threads are operating on the same aspect
(essentially copies of a FieldContainer (FC) that are associated with
threads) and modify the same FC. This can be problematic since changes
are recorded in a per-thread CL, but each aspect copy of a FC only has
one pointer to a CL entry. If, for example, thread A is the first to
modify a FC f then f._pContainerChanges is set up to point into the CL
of A. If later a thread B on the same aspect copy also modifies f the
change should be recorded in the CL of B, but since f._pContainerChanges
already exists that record is just augmented to also store the latter
change.
Whether that is a problem in practice is hard to say in general.

Post by Благоја Стојкоски
That's why I decided to ask you guys. Also I would like to ask you if
you could point me to some other sources of documentation or tutorials
for the latest OpenSG, apart from the wiki on http://www.opensg.org/ and
the documentation on http://opensg.fraunhofer.sg?

I don't think we have any.

Cheers,
Carsten

[Благоја Стојкоски]

Hey,

Thanks a lot. I guess I'll revert the change, and see if I can find another
way to lose the warning.

Regards,
Blagoja Stojkoski

On Fri, Sep 19, 2014 at 9:32 AM, Carsten Neumann <

Post by Carsten Neumann
Hello,

Post by Благоја Стојкоски
Now, the scenario that I have is, I have 4 threads whose changes get

OSG::Thread::getCurrentChangeList()->merge(*my_threads[i]->getChangeList());

Post by Благоја Стојкоски
This is done in a for cycle that goes through all the threads.
my_threads is an array of OSG::ThreadRefPtr
my_threads[i]->getChangeList()->clear();
This is where the warning message appears. It gets generated in the
FieldContainer.cpp file in line 322
(

http://sourceforge.net/p/opensg/code/ci/master/tree/Source/Base/FieldContainer/Base/OSGFieldContainer.cpp#l322
)

Post by Благоја Стојкоски
my_threads[i]->getCurrentChangeList()->clear();
However, I cannot find what is the difference between getChangeList and
getCurrentChangeList, so I can not be sure if what I did is correct.
When testing the program with this change in place, I can not spot
anything wrong, but I just want to be sure.

I doubt this does what you want it to do: Thread::getCurrentChangeList()
is a static member function that returns the ChangeList (CL) of the
thread executing the code, while getChangeList is a (non-static) member
function that returns the CL of the thread object it is called on. So
after the change you are only clearing the current threads CL, not those
you've merged from.
The message warns that multiple threads are operating on the same aspect
(essentially copies of a FieldContainer (FC) that are associated with
threads) and modify the same FC. This can be problematic since changes
are recorded in a per-thread CL, but each aspect copy of a FC only has
one pointer to a CL entry. If, for example, thread A is the first to
modify a FC f then f._pContainerChanges is set up to point into the CL
of A. If later a thread B on the same aspect copy also modifies f the
change should be recorded in the CL of B, but since f._pContainerChanges
already exists that record is just augmented to also store the latter
change.
Whether that is a problem in practice is hard to say in general.

Post by Благоја Стојкоски
That's why I decided to ask you guys. Also I would like to ask you if
you could point me to some other sources of documentation or tutorials
for the latest OpenSG, apart from the wiki on http://www.opensg.org/ and
the documentation on http://opensg.fraunhofer.sg?

I don't think we have any.
Cheers,
Carsten
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