From: Francesco Montorsi <f18m_cpp217828@yahoo.it>
Date: Sat, 20 Dec 2008 21:26:25 +0000 (+0000)
Subject: mention multi-core systems and wxThread::GetCPUCount
X-Git-Url: https://git.saurik.com/wxWidgets.git/commitdiff_plain/c6427d4da424cadbea08b70e964ab1a93246f67d

mention multi-core systems and wxThread::GetCPUCount

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@57448 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
---

diff --git a/docs/doxygen/overviews/thread.h b/docs/doxygen/overviews/thread.h
index 2734495583..08327e2993 100644
--- a/docs/doxygen/overviews/thread.h
+++ b/docs/doxygen/overviews/thread.h
@@ -10,12 +10,12 @@
 
 @page overview_thread Multithreading
 
-Classes: wxThread, wxMutex, wxCriticalSection, wxCondition
+Classes: wxThread, wxThreadHelper, wxMutex, wxCriticalSection, wxCondition, wxSemaphore
 
 wxWidgets provides a complete set of classes encapsulating objects necessary in
 multithreaded (MT) programs: the wxThread class itself and different
 synchronization objects: mutexes (see wxMutex) and critical sections (see
-wxCriticalSection)  with conditions (see wxCondition). The thread API i
+wxCriticalSection)  with conditions (see wxCondition). The thread API in
 wxWidgets resembles to POSIX1.c threads API (a.k.a. pthreads), although several
 functions have different names and some features inspired by Win32 thread API
 are there as well.
@@ -27,22 +27,24 @@ for large projects. Before starting an MT application (or starting to add MT
 features to an existing one) it is worth asking oneself if there is no easier
 and safer way to implement the same functionality. Of course, in some
 situations threads really make sense (classical example is a server application
-which launches a new thread for each new client), but in others it might be a
-very poor choice (example: launching a separate thread when doing a long
-computation to show a progress dialog). Other implementation choices are
-available: for the progress dialog example it is far better to do the
-calculations in the idle handler (see wxIdleEvent) or even simply do everything
-at once but call wxWindow::Update() periodically to update the screen.
-
-If you do decide to use threads in your application, it is strongly recommended
-that no more than one thread calls GUI functions. The thread sample shows that
-it @e is possible for many different threads to call GUI functions at once (all
-the threads created in the sample access GUI), but it is a very poor design
-choice for anything except an example. The design which uses one GUI thread and
-several worker threads which communicate with the main one using events is much
-more robust and will undoubtedly save you countless problems (example: under
-Win32 a thread can only access GDI objects such as pens, brushes, c created by
-itself and not by the other threads).
+which launches a new thread for each new client), but in others it might be an
+overkill. On the other hand, the recent evolution of the computer hardware shows
+an important trend towards multi-core systems, which are better exploited using
+multiple threads (e.g. you may want to split a long task among as many threads
+as many CPU (cores) the system reports; see wxThread::GetCPUCount).
+
+To implement non-blocking operations without using multiple threads you have
+two other possible implementation choices:
+- using wxIdleEvent (e.g. to perform a long calculation while updating a progress dialog)
+- simply do everything at once but call wxWindow::Update() periodically to update the screen.
+
+Even if there are the ::wxMutexGuiEnter and ::wxMutexGuiLeave functions which allows
+to use GUI functions from multiple threads, if you do decide to use threads in your
+application, it is strongly recommended that <b>no more than one calls GUI functions</b>.
+The design which uses one GUI thread and several worker threads which communicate
+with the main one using @b events is much more robust and will undoubtedly save you
+countless problems (example: under Win32 a thread can only access GDI objects such
+as pens, brushes, c created by itself and not by the other threads).
 
 For communication between secondary threads and the main thread, you may use
 wxEvtHandler::QueueEvent or its short version ::wxQueueEvent. These functions
@@ -54,5 +56,8 @@ yourself. In particular, please note that it is not enough to derive
 your class from wxThread and wxEvtHandler to send messages to it: in fact, this
 does not work at all.
 
+See also the @sample{thread} for a sample showing some simple interactions
+between the main and secondary threads.
+
 */
 
diff --git a/interface/wx/thread.h b/interface/wx/thread.h
index b167648634..2bb854a14b 100644
--- a/interface/wx/thread.h
+++ b/interface/wx/thread.h
@@ -972,6 +972,10 @@ public:
     /**
         Returns the number of system CPUs or -1 if the value is unknown.
 
+        For multi-core systems the returned value is typically the total number
+        of @e cores, since the OS usually abstract a single N-core CPU
+        as N different cores.
+
         @see SetConcurrency()
     */
     static int GetCPUCount();
@@ -1634,7 +1638,7 @@ bool wxIsMainThread();
         wxMutexGuiEnter();
 
         // Call GUI here:
-        my_window-DrawSomething();
+        my_window->DrawSomething();
 
         wxMutexGuiLeave();
     }