diff options
Diffstat (limited to 'docs/tutorials/016/page01.html')
| -rw-r--r-- | docs/tutorials/016/page01.html | 84 |
1 files changed, 0 insertions, 84 deletions
diff --git a/docs/tutorials/016/page01.html b/docs/tutorials/016/page01.html deleted file mode 100644 index 8781d692e14..00000000000 --- a/docs/tutorials/016/page01.html +++ /dev/null @@ -1,84 +0,0 @@ -<HTML> -<HEAD> - <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> - <META NAME="Author" CONTENT="James CE Johnson"> - <TITLE>ACE Tutorial 016</TITLE> -</HEAD> -<BODY TEXT="#000000" BGCOLOR="#FFFFFF" LINK="#000FFF" VLINK="#FF0F0F"> - -<CENTER><B><FONT SIZE=+2>ACE Tutorial 016</FONT></B></CENTER> - -<CENTER><B><FONT SIZE=+2>Making ACE_Condition easier to use</FONT></B></CENTER> - -<P> -<HR WIDTH="100%"> -The ACE framework has quite a few objects for syncronizing your -threads and even processes. We've mentioned a few in passing already: - ACE_Thread_Mutex and ACE_Barrier for instance. -<P> -Another interesting one is the ACE_Condition template. By using an -ACE_Condition you can have your code wait for an arbitrary condition -to occur. That condition is "embodied" in a variable of your choice. -That variable can, in turn, be any data type you wish. This makes -ACE_Condition much more flexible than a simple mutex, barrier or -semaphore. -<P> -In this tutorial, I'll create a wrapper class around the ACE_Condition -and the assorted housekeeping items necessary to make it work. I'll -use a simple integer as the condition variable but keep in mind that -you can use any data type you want. -<P> -Kirthika's abstract: -<ul> -An ACE_Condition class is a synchronisation mechanism employed in -situations where one or more threads cannot access the shared resource -unless some 'condition' becomes true. The ACE_Condition is associated -with a Mutex-lock which is released before blocking internally in the -wait call. Once the blocked thread is signaled to wake up again it -internally re-acquires the lock before checking the condition. -Unless the condition is true and it has the lock, it cant go ahead. -Once the shared resource is freed, a signal is sent to the waiting -threads which can now contend for the lock and access the resource. -<P> -Pizza-delivery metaphor: (courtesy Dr.Schmidt) -<ul> -Pizza delivery boy -- thread<br> -keys to delivery van -- mutex-lock<br> -pizza ready for delivery -- condition<br> -</Ul> -Situation: <br> -<ul> -Five pizza delivery boys use the same van. While the van is -unavailable, the boys go to sleep. When the van returns and the keys -are returned, the current user of the van nudges the other sleeping boys -to wake up and fight for the keys. Once the keys are obtained and the -pizza -is ready and out of the kitchen, the boy with the pizza and the keys can -now deliver it. -</ul> -<P> -This tutorial makes use of a wrapper class around the ACE_Condition and -uses a integer value as the condition. The four kinds of condition -implemented -are: !=, >=, <=, == by using C++ operator overloading. Guards are used -within -the methods to make sure that the method is thread-safe. Once the thread -completes -its job, it broadcasts to the waiting on it. -<P> -An ACE_Task is used to stress test the various conditions. -A test object is created for each condition and the main thread waits -until the condition becomes true. For instance: <= condition: -Five threads are spwaned which in turn increment the condition -variable, which is initialised to 1 by 2. Remember that you are waiting -on -the <= condition. So once 3 threads have been thru it, the value becomes -6 -and the condition becomes true! -<P> -This simple example shows us how to program and use the Condition -variable for -synchronisation. -</ul> -<P><HR WIDTH="100%"> -<CENTER>[<A HREF="../online-tutorials.html">Tutorial Index</A>] [<A HREF="page02.html">Continue This Tutorial</A>]</CENTER> |