Random Numbers and NTL
According to its website, the Number Theory Library (NTL) is a:
high-performance, portable C++ library providing data structures and algorithms for manipulating signed, arbitrary length integers, and for vectors, matrices, and polynomials over the integers and over finite fields.
I have been using it a lot because of the Cryptography class that I’m in this semester, and something that I need to do frequently is generate random numbers.
To do this, seeding is frequently required, and the NTL is no different, but it took a while for me to actually get it to work. The following will seed the random functions provided by the NTL ZZ class:
ZZ number, seed; srand(getpid()); seed << ((long) GetTime() ^ rand()); SetSeed(seed); RandomLen(number, rand() % 300);
Stick that at the top of your main() and you should be all set.
Also, does anyone know of a shorter, possibly easier to remember, way to do this? If so, the comments are open.
December 8th, 2008 23:03
Ryan,
I used random ZZ’s pretty extensively in the code for my honors thesis. Looking back at the code I see that all I did was this:
srand ( time(NULL) );
SetSeed( to_ZZ(rand()) );
Then to get a random ZZ, I called:
ZZ x = RandomBnd(N);
which gives you 0 <= x <= N. Perhaps this isn’t the “most secure” or “random” way to do it, but it’s definitely easier and shorter.
Good luck!
Jeff
December 9th, 2008 01:24
Cool! I knew there had to be an easier way, thanks for replying!
January 6th, 2010 17:36
#include
SetSeed(to_ZZ(clock()));
January 6th, 2010 17:40
that should be include time.h