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6 multithreading_support - Multithreading Support in Coin
7 The support in Coin for using multiple threads in application programs
9 and the Coin library itself, consists of two main features:
10 • Coin provides platform-independent thread-handling abstraction
12 classes. These are classes that the application programmer can freely
13 use in her application code to start new threads, control their
14 execution, work with mutexes and do other tasks related to handling
15 multiple threads.
16 The classes in question are SbThread, SbMutex, SbStorage, SbBarrier,
17 SbCondVar, SbFifo, SbThreadAutoLock, SbRWMutex, and SbTypedStorage. See
18 their respective documentation for the detailed information.
19 The classes fully hides the system-specific implementation, which is
20 either done on top of native Win32 (if on Microsoft Windows), or over
21 POSIX threads (on UNIX and UNIX-like systems).
22 • The other aspect of our multi-threading support is that Coin can be
23 specially configured so that rendering traversals of the scene graph
24 are done in a thread-safe manner. This means e.g. that it is possible
25 to have Coin render the scene in parallel on multiple CPUs for
26 multiple rendering pipes, to better take advantage of such high-end
27 systems (like CAVE environments, for instance).
28 Thread-safe render traversals are off by default, because there is a
29 small overhead involved which would make rendering (very) slightly
30 slower on single-threaded invocations.
31 To get a Coin library built with thread-safe rendering, one must
32 actively re-configure Coin and build a special, local version. For
33 configure-based builds (UNIX and UNIX-like systems, or with Cygwin on
34 Microsoft Windows) this is done with the option '--enable-threadsafe'
35 to Autoconf configure. For how to change the configuration and re-build
36 with Visual Studio, get in touch with us at 'coin-support@coin3d.org'.
37 There are some restrictions and other issues which it is important to
38 be aware of:
39 • We do not yet provide any support for binding the multi-threaded
40 rendering support into the SoQt / SoWin / etc GUI bindings, and
41 neither do we provide bindings against any specific library that
42 handles multi-pipe rendering. This means the application programmer
43 will have to possess some expertise, and put in some effort, to be
44 able to utilize multi-pipe rendering with Coin.
45 • Rendering traversals is currently the only operation which we
46 publicly support to be thread-safe. There are other aspects of Coin
47 that we know are thread-safe, like most other action traversals
48 beside just rendering, but we make no guarantees in this regard.
49 • Be careful about using a separate thread for changing Coin structures
50 versus what is used for the application's GUI event thread.
51 We are aware of at least issues with Qt (and thereby SoQt), where you
52 should not modify the scene graph in any way in a thread separate from
53 the main Qt thread. This because it will trigger operations where Qt is
54 not thread-safe.
55 Since
56 Coin 2.0
57Coin 2.5.0" multithreading_support(3Version)