... and now it's fixed

Next, the good news: I've found and fixed the bug, and committed the fix to the boost Subversion repository. If you can't update your boost implementation to trunk, you can download the new code and replace boost/thread/win32/condition_variable.hpp from the boost 1.35.0 distribution with the new version.

What was it?

For those of you interested in the details, this bug was in code related to detecting (and preventing) spurious wakes. When a condition variable was notified with notify_one(), the implementation was choosing one or more threads to compete for the notify. One of these would get the notification and return from wait(). Those that didn't get the notify were supposed to resume waiting without returning from wait(). Unfortunately, this left a potential gap where those threads weren't waiting, so would miss any calls to notify_one() that occurred before those threads resumed waiting.

The fix was to rewrite the wait/notify mechanism so this gap no longer exists, by changing the way that waiting threads are counted.

Posted by Anthony Williams
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Tags: boost, thread, condition variable, windows
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The Future of Concurrency in C++: Slides from ACCU 2008

Monday, 07 April 2008

My presentation on The Future of Concurrency in C++ at ACCU 2008 last Thursday went off without a hitch. I was pleased to find that my talk was well attended, and the audience had lots of worthwhile questions — hopefully I answered them to everybody's satisfaction.

For those that didn't attend, or for those that did, but would like a reminder of what I said, here are the slides from my presentation.

Posted by Anthony Williams
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Tags: concurrency, multithreading, C++, ACCU
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Boost 1.35.0 has been Released!

Tuesday, 01 April 2008

Verson 1.35.0 of the Boost libraries was released on Saturday. This release includes a major revision of the Boost.Thread library, to bring it more in line with the C++0x Thread Library. There are many new libraries, and revisions to other libraries too, see the full Release Notes for details, or just Download the release and give it a try.

Posted by Anthony Williams
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Tags: boost
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Optimizing Applications with Fixed-Point Arithmetic

Tuesday, 01 April 2008

My latest article, Optimizing Math-intensive Applications with Fixed Point Arithmetic from the April 2008 issue of Dr Dobb's Journal is now available online. (I originally had "Maths-intensive" in the title, being English, but they dropped the "s", being American).

In the article, I describe the fixed-point techniques I used to vastly improve the performance of an application using sines, cosines and exponentials without hardware floating point support.

The source code referenced in the article can be downloaded from here. It is released under the Boost Software License.

Posted by Anthony Williams
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Tags: optimization, fixed-point, maths
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