mfactorial
Recently, I was playing around with the GNU Multiple Precision Arithmetic Library. While most of the resulting code snippets are pretty much useless, the attached C program might be worth a blog entry. It calculates the factorial of a given number. At first glance, nothing special at all, but it does this task rather fast:
/* Naive algorithm*/ time ./fak 500000 > /dev/null real 2m4.756s user 2m4.637s sys 0m0.094s /*mfactorial*/ time ./mfactorial 500000 > /dev/null real 0m7.855s user 0m13.226s sys 0m0.050s
Maybe I'll re-implement the whole thing using a real clever algorithm (e.g. split-recursive) some day, but for now, I'm content with the current speed. :-)
BTW: The compiling instructions are included in the *.c file