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git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@1388 f3b2605a-c512-4ea7-a41b-209d697bcdaa

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sjplimp
2008-01-18 17:18:46 +00:00
parent 89beb4487e
commit 17416f49f4
8 changed files with 36 additions and 42 deletions
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62
src/random_park.cpp
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@ -95,54 +95,44 @@ void RanPark::reset(int seed_init)
}
/* ----------------------------------------------------------------------
reset the seed based on atom position within box and ibase = caller seed
combine 3 RNGs based on fractional position in box into one new seed
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)
{
// for orthogonal box, lamda = fractional position in box
// for triclinic box, convert to lamda coords
int i;
double lamda[3];
char *str = (char *) &ibase;
int n = sizeof(int);
if (domain->triclinic == 0) {
lamda[0] = (coord[0] - domain->boxlo[0]) / domain->prd[0];
lamda[1] = (coord[1] - domain->boxlo[1]) / domain->prd[1];
lamda[2] = (coord[2] - domain->boxlo[2]) / domain->prd[2];
} else domain->x2lamda(coord,lamda);
unsigned int hash = 0;
for (i = 0; i < n; i++) {
hash += str[i];
hash += (hash << 10);
hash ^= (hash >> 6);
}
// seed 1,2,3 = combination of atom coord in each dim and user-input seed
// map geometric extent into range of each of 3 RNGs
// warm-up each RNG by calling it twice
str = (char *) coord;
n = 3 * sizeof(double);
for (i = 0; i < n; i++) {
hash += str[i];
hash += (hash << 10);
hash ^= (hash >> 6);
}
int seed1,seed2,seed3;
hash += (hash << 3);
hash ^= (hash >> 11);
hash += (hash << 15);
seed1 = static_cast<int> (lamda[0] * IM1);
seed1 = (seed1+ibase) % IM1;
seed1 = (seed1*IA1+IC1) % IM1;
seed1 = (seed1*IA1+IC1) % IM1;
// keep 31 bits of unsigned int as new seed
seed2 = static_cast<int> (lamda[1] * IM2);
seed2 = (seed2+ibase) % IM2;
seed2 = (seed2*IA2+IC2) % IM2;
seed2 = (seed2*IA2+IC2) % IM2;
seed = hash & 0x7ffffff;
seed3 = static_cast<int> (lamda[2] * IM3);
seed3 = (seed3+ibase) % IM3;
seed3 = (seed3*IA3+IC3) % IM3;
seed3 = (seed3*IA3+IC3) % IM3;
// warm up the RNG
// fraction = 0-1 with giving each dim an equal weighting
// use fraction to reset Park/Miller RNG seed
// warm-up master RNG with new seed by calling it twice
double fraction = 1.0*seed1/(3*IM1) + 1.0*seed2/(3*IM2) + 1.0*seed3/(3*IM3);
seed = static_cast<int> (fraction*IM) + 1;
if (seed >= IM) seed = IM-1;
uniform();
uniform();
for (i = 0; i < 5; i++) uniform();
}
/* ---------------------------------------------------------------------- */