C programming question

[arkal]

Hey guys,

I'm writing a c code which requires me to choose a random location within the entire genome. Using rand() or lrand48() functions the max attainable value is ~2.1 x 10^9 which is roughly 2/3 of the size of the human genome (~ 3.1x 10^9). Can i get some suggestions on how to choose the location over the genome? I have 2 ideas but i'm not sure of they're ok...

1. add (2*rand() )%genome size
2. (rand() + rand() )%genome size()
3. (rand() * (rand()%1,500,000,000) )%genome_size

1 and 2 will favour larger numbers and i have no idea wat 3 will give

Thanx in advance!
-Arkal

[tomc]

include a RNG of your choice instead of the built in ones if they are insufficient
there many to choose from. Maybe a "Mersenne twister" here is an implementation http://www.cs.hmc.edu/~geoff/mtwist.html (no affiliation)

features claim "Variety of formats: integer and double, 32- and 64-bit. "