Dear User’s,
I just want to know whether I can control the random number generator in LAMMPS, such a way that I can apply two different force (Random force in the Langevin equation) at the same time on two different particles in the simulation system. For Example, I want to apply different Random force on two Particles A and B throughout the simulation. I think if I am using the same seed for all, then it will apply the same random force for all particle at a particular step. So If I need to have different random forces on A and B in each step during the simulation. How one can achieve this in LAMMPS? Please help me with your suggestions…
-Rahul
First off. It is very bad to make claims about a software without actually reading the source code or or making experiments proving those claims. It is particularly bad for a scientist to act this “unscientific”.
Dear User’s,
I just want to know whether I can control the random number generator in LAMMPS, such a way that I can apply two different force (Random force in the Langevin equation) at the same time on two different particles in the simulation system. For Example, I want to apply different Random force on two Particles A and B throughout the simulation. I think if I am using the same seed for all, then it will apply the same random force for all particle at a particular step.
that is not correct and is assuming that the people who implemented and maintain this piece of code are quite incompetent. you can see for yourself by looking at the source code: https://github.com/lammps/lammps/blob/master/src/fix_langevin.cpp#L524
fix langevin is retrieving a new (pseudo) number from a uniform distribution for each direction for each particle. Also since the random number generator seed is augmented by the MPI processor rank, you will have a different seed and thus sequence of random numbers depending on how many MPI ranks (or processors) are used.
https://github.com/lammps/lammps/blob/master/src/fix_langevin.cpp#L85
So If I need to have different random forces on A and B in each step during the simulation. How one can achieve this in LAMMPS? Please help me with your suggestions…
my suggestion is, that you please research more carefully before making unsubstantiated claims and asking questions that don’t need to be answered.
thanks in advance,
axel.
Thank you sir for your time and explanation.
First off. It is very bad to make claims about a software without actually reading the source code or or making experiments proving those claims. It is particularly bad for a scientist to act this “unscientific”.
Dear User’s,
I just want to know whether I can control the random number generator in LAMMPS, such a way that I can apply two different force (Random force in the Langevin equation) at the same time on two different particles in the simulation system. For Example, I want to apply different Random force on two Particles A and B throughout the simulation. I think if I am using the same seed for all, then it will apply the same random force for all particle at a particular step.
that is not correct and is assuming that the people who implemented and maintain this piece of code are quite incompetent. you can see for yourself by looking at the source code: https://github.com/lammps/lammps/blob/master/src/fix_langevin.cpp#L524
fix langevin is retrieving a new (pseudo) number from a uniform distribution for each direction for each particle. Also since the random number generator seed is augmented by the MPI processor rank, you will have a different seed and thus sequence of random numbers depending on how many MPI ranks (or processors) are used.
https://github.com/lammps/lammps/blob/master/src/fix_langevin.cpp#L85
So If I need to have different random forces on A and B in each step during the simulation. How one can achieve this in LAMMPS? Please help me with your suggestions…
my suggestion is, that you please research more carefully before making unsubstantiated claims and asking questions that don’t need to be answered.
thanks in advance,
axel.