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Adding an improved error estimator for MSM. 

git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@8930 f3b2605a-c512-4ea7-a41b-209d697bcdaa
This commit is contained in:
pscrozi 2012-10-10 00:15:14 +00:00
parent c8b5b72c96
commit 506f99afab
2 changed files with 62 additions and 30 deletions
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81
src/KSPACE/msm.cpp
View File

@ -40,7 +40,6 @@
using namespace LAMMPS_NS;
using namespace MathConst;
#define MAXORDER 10
#define MAX_LEVELS 10
#define OFFSET 16384
#define SMALL 0.00001
@ -80,6 +79,8 @@ MSM::MSM(LAMMPS *lmp, int narg, char **arg) : KSpace(lmp, narg, arg)
v3_direct = v4_direct = v5_direct = NULL;
levels = 0;
order = 4;
differentiation_flag = 1;
}
@ -134,15 +135,13 @@ void MSM::init()
if (domain->nonperiodic > 0)
error->all(FLERR,"Cannot (yet) use nonperiodic boundaries with MSM");
if (order == 5) order = 4; // Change the default order value
if (order < 4 || order > MAXORDER) {
if (order < 4 || order > 10) {
char str[128];
sprintf(str,"MSM order cannot be < 2 or > than %d",MAXORDER);
sprintf(str,"MSM order must be 4, 6, 8, or 10");
error->all(FLERR,str);
}
if (order%2 != 0) error->all(FLERR,"MSM order must be even");
if (order%2 != 0) error->all(FLERR,"MSM order must be 4, 6, 8, or 10");
// free all arrays previously allocated
@ -459,15 +458,55 @@ void MSM::init()
}
/* ----------------------------------------------------------------------
estimate 1d grid RMS force error for MSM from Sec 3.1 of Hardy's thesis
estimate 1d grid RMS force error for MSM
------------------------------------------------------------------------- */
double MSM::estimate_1d_error(double h, double prd)
{
double a = cutoff;
int p = order - 1;
double error_1d = pow(h,(p-1))/pow(a,(p+1));
error_1d *= 24.0*q2/sqrt(atom->natoms*a*prd*prd);
double Mp,cprime,error_scaling;
Mp = cprime = error_scaling = 1;
// Mp values from Table 5.1 of Hardy's thesis
// cprime values from equation 4.17 of Hardy's thesis
// error scaling from empirical fitting to convert to rms force errors
if (p == 3) {
Mp = 9;
cprime = 1.0/6.0;
if (differentiation_flag) error_scaling = 0.39189561;
else error_scaling = 0.215328372;
} else if (p == 5) {
Mp = 825;
cprime = 1.0/30.0;
if (differentiation_flag) error_scaling = 0.150829428;
else error_scaling = 0.10751471;
} else if (p == 7) {
Mp = 130095;
cprime = 1.0/140.0;
if (differentiation_flag) error_scaling = 0.049632967;
else error_scaling = 0.047579461;
} else if (p == 9) {
Mp = 34096545;
cprime = 1.0/630.0;
if (differentiation_flag) error_scaling = 0.013520855;
else error_scaling = 0.010403771;
} else {
error->all(FLERR,"MSM order must be 4, 6, 8, or 10");
}
// equation 4.1 from Hardy's thesis
double C_p = 4.0*cprime*Mp/3.0;
// use empirical parameters to convert to rms force errors
C_p *= error_scaling;
// equation 3.197 from Hardy's thesis
double error_1d = C_p*pow(h,(p-1))/pow(a,(p+1));
// include dependency of error on other terms
error_1d *= q2*a/(prd*sqrt(atom->natoms));
return error_1d;
}
@ -1097,12 +1136,10 @@ void MSM::set_grid()
if (screen) {
fprintf(screen," grid = %d %d %d\n",nx_msm[0],ny_msm[0],nz_msm[0]);
fprintf(screen," stencil order = %d\n",order);
fprintf(screen," splitting order = %d\n",split_order);
}
if (logfile) {
fprintf(logfile," grid = %d %d %d\n",nx_msm[0],ny_msm[0],nz_msm[0]);
fprintf(logfile," stencil order = %d\n",order);
fprintf(logfile," splitting order = %d\n",split_order);
}
}
@ -1812,19 +1849,19 @@ void MSM::prolongation(int n)
egrid1[kk][jj][ii] += egrid2[kp][jp][ip] * phi3d;
}
if (!differentiation_flag) {
fxgrid1[kk][jj][ii] += fxgrid2[kp][jp][ip] * phi3d;
fygrid1[kk][jj][ii] += fygrid2[kp][jp][ip] * phi3d;
fzgrid1[kk][jj][ii] += fzgrid2[kp][jp][ip] * phi3d;
}
if (!differentiation_flag) {
fxgrid1[kk][jj][ii] += fxgrid2[kp][jp][ip] * phi3d;
fygrid1[kk][jj][ii] += fygrid2[kp][jp][ip] * phi3d;
fzgrid1[kk][jj][ii] += fzgrid2[kp][jp][ip] * phi3d;
}
if (vflag_atom) {
v0grid1[kk][jj][ii] += v0grid2[kp][jp][ip] * phi3d;
v1grid1[kk][jj][ii] += v1grid2[kp][jp][ip] * phi3d;
v2grid1[kk][jj][ii] += v2grid2[kp][jp][ip] * phi3d;
v3grid1[kk][jj][ii] += v3grid2[kp][jp][ip] * phi3d;
v4grid1[kk][jj][ii] += v4grid2[kp][jp][ip] * phi3d;
v5grid1[kk][jj][ii] += v5grid2[kp][jp][ip] * phi3d;
v0grid1[kk][jj][ii] += v0grid2[kp][jp][ip] * phi3d;
v1grid1[kk][jj][ii] += v1grid2[kp][jp][ip] * phi3d;
v2grid1[kk][jj][ii] += v2grid2[kp][jp][ip] * phi3d;
v3grid1[kk][jj][ii] += v3grid2[kp][jp][ip] * phi3d;
v4grid1[kk][jj][ii] += v4grid2[kp][jp][ip] * phi3d;
v5grid1[kk][jj][ii] += v5grid2[kp][jp][ip] * phi3d;
}
}

11
src/KSPACE/msm.h
View File

@ -154,15 +154,10 @@ E: Cannot use slab correction with MSM
Slab correction can only be used with Ewald and PPPM, not MSM
E: MSM order cannot be < 4 or > than 10
E: MSM order must be 4, 6, 8, or 10
This is a limitation of the MSM implementation in LAMMPS.
Currently the order may only range from 4 to 10
E: MSM order must be even
Currently the MSM order must be an even number
This is a limitation of the MSM implementation in LAMMPS:
the MSM order can only be 4, 6, 8, or 10.
E: KSpace style is incompatible with Pair style