modify random_park

Dear lammps users/developers
I am interested in an energy distribution function as the link below
https://www.boost.org/doc/libs/1_41_0/libs/math/doc/sf_and_dist/html/math_toolkit/dist/dist_ref/dists/f_dist.html

In order to do this, I need to modify random_park available in lammps/src. But this script is a pseudo-random number generator (PRNG) and not a real one. How I can make a PRNG that gives similar results to that available in the link?
Kind regards,
Movaffaq Kateb

all RNGs used in simulations are pRNGs. for “real”, i.e. those suitable for cryptography, you need access to an external source of entropy.

Specific distributions are usually generated from uniformly distributed RN from a pRNG. Those transformations are included in the classes, but that is purely convenience, not a requirement.
thus for your case, since you need to modify code, you can either use the internal pRNGs in LAMMPS or implement your own. Please note that the pRNG in ran_park.cpp is a fast but rather low quality one. It is used for example to set initial velocities, where high quality RNGs are not needed as the dynamics of the system during equilibration will make it “forget” the initial state quickly. The pRNG in ran_mars.cpp is much better.

Axel.

Dear Axel
Thank you for the clarification.

Regards,
MK