GUI applications written in XPCE can benefit from the multi-threaded version of XPCE/SWI-Prolog if they need to do expensive computations that block to UI in the single-threaded version.
Due to various technical problems on both Windows and Unix/X11 threading is best exploited by handing long computations to their own thread.
The XPCE message passing system is guarded with a single mutex, which synchronises both access from Prolog and activation through the GUI. In MS-Windows, GUI events are processed by the thread that created the window in which the event occurred, whereas in Unix/X11 they are processed by the thread that dispatches messages.
Some tentative work is underway to improve the integration between XPCE and multi-threaded SWI-Prolog.
pce for XPCE
event-handling. In the X11 version this call creates a thread that
executes the X11 event-dispatch loop. In MS-Windows it creates a thread
that executes a windows event-dispatch loop. The XPCE event-handling
thread has the alias pce. Options specifies the
thread-attributes as thread_create/3.
pce thread, executing it
synchronous with the thread's event-loop. The pce_call/1
predicate returns immediately without waiting. Note that Goal
is copied to the pce thread.
For further information about XPCE in threaded applications, please visit http://gollem.swi.psy.uva.nl/twiki/pl/bin/view/Development/MultiThreadsXPCE