From:
Obfuscated C Code

We find:
http://www.cise.ufl.edu/~manuel/obfuscate/pi.c

To check the output online:
C code - 21 lines - codepad

Yes, the program as it is pasted there gives a poor approximation, however... the accuracy of the calculation increases as the circle diameter is increased. I've stared at this for a little while but can't seem to make sense of what's actually going on, do any of you have insight in to the program flow and what the statements are executing?