1multithreading_support(3)            Coin            multithreading_support(3)
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NAME

6       multithreading_support - Multithreading Support in Coin The support in
7       Coin for using multiple threads in application programs and the Coin
8       library itself, consists of two main features:
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10       • Coin provides platform-independent thread-handling abstraction
11         classes. These are classes that the application programmer can freely
12         use in her application code to start new threads, control their
13         execution, work with mutexes and do other tasks related to handling
14         multiple threads.
15       The classes in question are SbThread, SbMutex, SbStorage, SbBarrier,
16       SbCondVar, SbFifo, SbThreadAutoLock, SbRWMutex, and SbTypedStorage. See
17       their respective documentation for the detailed information.
18       The classes fully hides the system-specific implementation, which is
19       either done on top of native Win32 (if on Microsoft Windows), or over
20       POSIX threads (on UNIX and UNIX-like systems).
21       • The other aspect of our multi-threading support is that Coin can be
22         specially configured so that rendering traversals of the scene graph
23         are done in a thread-safe manner. This means e.g. that it is possible
24         to have Coin render the scene in parallel on multiple CPUs for
25         multiple rendering pipes, to better take advantage of such high-end
26         systems (like CAVE environments, for instance).
27       Thread-safe render traversals are off by default, because there is a
28       small overhead involved which would make rendering (very) slightly
29       slower on single-threaded invocations.
30       To get a Coin library built with thread-safe rendering, one must
31       actively re-configure Coin and build a special, local version. For
32       configure-based builds (UNIX and UNIX-like systems, or with Cygwin on
33       Microsoft Windows) this is done with the option '--enable-threadsafe'
34       to Autoconf configure. To change the configuration and re-build with
35       Visual Studio, you will need to change the preprocessor directive
36       COIN_THREADSAFE to defined in the file src/setup.h located in the same
37       folder as you found your solution file.
38       There are some restrictions and other issues which it is important to
39       be aware of:
40       • We do not yet provide any support for binding the multi-threaded
41         rendering support into the SoQt / SoWin / etc GUI bindings, and
42         neither do we provide bindings against any specific library that
43         handles multi-pipe rendering. This means the application programmer
44         will have to possess some expertise, and put in some effort, to be
45         able to utilize multi-pipe rendering with Coin.
46       • Rendering traversals is currently the only operation which we
47         publicly support to be thread-safe. There are other aspects of Coin
48         that we know are thread-safe, like most other action traversals
49         beside just rendering, but we make no guarantees in this regard.
50       • Be careful about using a separate thread for changing Coin structures
51         versus what is used for the application's GUI event thread.
52       We are aware of at least issues with Qt3 (and thereby SoQt), where you
53       should not modify the scene graph in any way in a thread separate from
54       the main Qt thread. This because it will trigger operations where Qt3
55       is not thread-safe. For Qt4, we have not been aware of such problems.
56       Since
57           Coin 2.0
58Version 4.0.0                   Mon Jan 25 2021      multithreading_support(3)
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