Integer factorization using Quadratic Sieve.
You will need GMP library arbitrary precision arithmetic and also the MPFR library for multiple-precision floating-point arithmetic.
The parameters defined in config.h can greatly change the integer
factorization speed to better or worse.
$ make
$ ./factor 32000104328923478923489234890234890234890890234
32000104328923478923489234890234890234890890234: 2 3 191 248041 2924794690724209 38490000553137727468841
$ ./factor 51884496199884033707060070710306434395690951779
51884496199884033707060070710306434395690951779: 10906804661271099530111 4757075771616259690952989
If you are running GNU/Linux there is a program factor in coreutils that can
be used for comparison. It uses Pollard-Rho as a integer factorization
technique but it does not work well on numbers which are the product of two large
prime numbers as seen below.
$ time ./factor 32000104328923478923489234890234890234890890234
32000104328923478923489234890234890234890890234: 2 3 191 248041 2924794690724209 38490000553137727468841
real 0m0.861s
user 0m0.848s
sys 0m0.012s
$ time ./factor 51884496199884033707060070710306434395690951779
51884496199884033707060070710306434395690951779: 10906804661271099530111 4757075771616259690952989
real 1m10.573s
user 1m10.477s
sys 0m0.022s
$ time factor 32000104328923478923489234890234890234890890234
32000104328923478923489234890234890234890890234: 2 3 191 248041 2924794690724209 38490000553137727468841
real 0m21.231s
user 0m21.212s
sys 0m0.002s
$ time factor 51884496199884033707060070710306434395690951779
// aborted after over 1 hour