136 lines
3.3 KiB
C++
136 lines
3.3 KiB
C++
/* ----------------------------------------------------------------------
|
|
LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
|
|
https://www.lammps.org/, Sandia National Laboratories
|
|
LAMMPS development team: developers@lammps.org
|
|
|
|
Copyright (2003) Sandia Corporation. Under the terms of Contract
|
|
DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
|
|
certain rights in this software. This software is distributed under
|
|
the GNU General Public License.
|
|
|
|
See the README file in the top-level LAMMPS directory.
|
|
------------------------------------------------------------------------- */
|
|
|
|
// Park/Miller RNG
|
|
|
|
#include "random_park.h"
|
|
|
|
#include "error.h"
|
|
|
|
#include <cmath>
|
|
|
|
using namespace LAMMPS_NS;
|
|
|
|
#define IA 16807
|
|
#define IM 2147483647
|
|
#define AM (1.0 / IM)
|
|
#define IQ 127773
|
|
#define IR 2836
|
|
|
|
/* ---------------------------------------------------------------------- */
|
|
|
|
RanPark::RanPark(LAMMPS *lmp, int seed_init) : Pointers(lmp)
|
|
{
|
|
if (seed_init <= 0) error->one(FLERR, "Invalid seed for Park random # generator");
|
|
seed = seed_init;
|
|
save = 0;
|
|
}
|
|
|
|
/* ----------------------------------------------------------------------
|
|
uniform RN
|
|
------------------------------------------------------------------------- */
|
|
|
|
double RanPark::uniform()
|
|
{
|
|
int k = seed / IQ;
|
|
seed = IA * (seed - k * IQ) - IR * k;
|
|
if (seed < 0) seed += IM;
|
|
double ans = AM * seed;
|
|
return ans;
|
|
}
|
|
|
|
/* ----------------------------------------------------------------------
|
|
gaussian RN
|
|
------------------------------------------------------------------------- */
|
|
|
|
double RanPark::gaussian()
|
|
{
|
|
double first, v1, v2, rsq, fac;
|
|
|
|
if (!save) {
|
|
do {
|
|
v1 = 2.0 * uniform() - 1.0;
|
|
v2 = 2.0 * uniform() - 1.0;
|
|
rsq = v1 * v1 + v2 * v2;
|
|
} while ((rsq >= 1.0) || (rsq == 0.0));
|
|
fac = sqrt(-2.0 * log(rsq) / rsq);
|
|
second = v1 * fac;
|
|
first = v2 * fac;
|
|
save = 1;
|
|
} else {
|
|
first = second;
|
|
save = 0;
|
|
}
|
|
return first;
|
|
}
|
|
|
|
/* ---------------------------------------------------------------------- */
|
|
|
|
void RanPark::reset(int seed_init)
|
|
{
|
|
if (seed_init <= 0) error->all(FLERR, "Invalid seed for Park random # generator");
|
|
seed = seed_init;
|
|
save = 0;
|
|
}
|
|
|
|
/* ----------------------------------------------------------------------
|
|
reset the seed based on atom coords and ibase = caller seed
|
|
use hash function, treating user seed and coords as sequence of input ints
|
|
this is Jenkins One-at-a-time hash, see Wikipedia entry on hash tables
|
|
------------------------------------------------------------------------- */
|
|
|
|
void RanPark::reset(int ibase, double *coord)
|
|
{
|
|
int i;
|
|
|
|
auto str = (char *) &ibase;
|
|
int n = sizeof(int);
|
|
|
|
unsigned int hash = 0;
|
|
for (i = 0; i < n; i++) {
|
|
hash += str[i];
|
|
hash += (hash << 10);
|
|
hash ^= (hash >> 6);
|
|
}
|
|
|
|
str = (char *) coord;
|
|
n = 3 * sizeof(double);
|
|
for (i = 0; i < n; i++) {
|
|
hash += str[i];
|
|
hash += (hash << 10);
|
|
hash ^= (hash >> 6);
|
|
}
|
|
|
|
hash += (hash << 3);
|
|
hash ^= (hash >> 11);
|
|
hash += (hash << 15);
|
|
|
|
// keep 31 bits of unsigned int as new seed
|
|
// do not allow seed = 0, since will cause hang in gaussian()
|
|
|
|
seed = hash & 0x7ffffff;
|
|
if (!seed) seed = 1;
|
|
|
|
// warm up the RNG
|
|
|
|
for (i = 0; i < 5; i++) uniform();
|
|
save = 0;
|
|
}
|
|
|
|
/* ---------------------------------------------------------------------- */
|
|
|
|
int RanPark::state()
|
|
{
|
|
return seed;
|
|
}
|