Saturday, March 28, 2009

Googletalk: "Getting C++ threads to work right"

I've been watching a few Google dev talks on Youtube. I thought I'd write up a summary of this one:

http://www.youtube.com/watch?v=mrvAqvtWYb4

In summary:
  • Writing "correct" thread code using the pthreads and CPU instructions (fencing, for example) requires the code to know whats going on under the hood;
  • Gluing concurrency to the "side" of a language which was specified without concurrency has shown to be a bit of a problem - eg, concurrent access to different variables in a structure and how various compilers have implemented this (eg, changing a byte in a struct becoming a 32 bit load, 8 bit modify, 32 bit store);
  • Most programmers should really use higher level constructs, like what C++0x and what the Java specification groups have been doing.
If you write threaded code or you're curious about it, you should watch this talk. It provides a very good overview of the problems and should open your mind up a little to what may go wrong..

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