[osg-submissions] Use atomic reference counts

[Mathias Fröhlich]

Hi Robert,

I have implemented threadsafe reference counting using atomic operations if 
available for the target platform.

There is a configure check which searches for different implementations and 
selects one that is available.

Based on that configure check, a file include/OpenThreads/Config is created 
that stores that configuration decision.

There are two new classes in OpenThreads that serve as an abstraction for the 
atomic operations. If no atomic value implementation is available at the 
target platform the class falls back to using mutexes. So this class is 
thread safe in any case.

Referenced is modified to use that atomic operations for reference counting 
and creation of the a mutex locked observer set pointer iff there is an 
implementation for the atomic data type *without* mutex available. If we have 
atomic operations with a mutex, the old strategy is used.

In effect I get a few percent framerate improovements for my test models with 
osgviewer compared to the case where we force thread safe reference counting 
by the environment variable for example. The non thread safe implementations 
delivers about the same frame rate than the atomic reference count one on 
x86_64.
The memory consumption of Referenced itself is one pointer fewer when using 
atomic ops.

I did not test that on windows so far, but took the implementation from some 
of my own codes that already works on windows.
In particular, I do not know if the cmake tests will work as is on windows.

The change is based on revision 8397.

Comments?

Mathias

-- 
Dr. Mathias Fröhlich, science + computing ag, Software Solutions
Hagellocher Weg 71-75, D-72070 Tuebingen, Germany
Phone: +49 7071 9457-268, Fax: +49 7071 9457-511
-- 
Vorstand/Board of Management:
Dr. Bernd Finkbeiner, Dr. Florian Geyer,
Dr. Roland Niemeier, Dr. Arno Steitz, Dr. Ingrid Zech
Vorsitzender des Aufsichtsrats/
Chairman of the Supervisory Board:
Prof. Dr. Hanns Ruder
Sitz/Registered Office: Tuebingen
Registergericht/Registration Court: Stuttgart
Registernummer/Commercial Register No.: HRB 382196 

-------------- next part --------------
A non-text attachment was scrubbed...
Name: referenced-8397.tar.bz2
Type: application/x-tbz
Size: 13390 bytes
Desc: not available
URL: <http://lists.openscenegraph.org/pipermail/osg-submissions-openscenegraph.org/attachments/20080602/7febf127/attachment.bin>