Merge pull request #378 from timattox/USER-DPD_ssa_update

USER-DPD: performance optimizations to ssa_update() in fix_shardlow
This commit is contained in:
sjplimp 2017-02-21 15:50:07 -07:00 committed by GitHub
commit cb9d42da08
2 changed files with 249 additions and 170 deletions

View File

@ -61,6 +61,7 @@ using namespace LAMMPS_NS;
using namespace FixConst;
#define EPSILON 1.0e-10
#define EPSILON_SQUARED ((EPSILON) * (EPSILON))
static const char cite_fix_shardlow[] =
"fix shardlow command:\n\n"
@ -197,212 +198,129 @@ void FixShardlow::setup(int vflag)
}
/* ----------------------------------------------------------------------
Perform the stochastic integration and Shardlow update
Perform the stochastic integration and Shardlow update for constant temperature
Allow for both per-type and per-atom mass
NOTE: only implemented for orthogonal boxes, not triclinic
------------------------------------------------------------------------- */
void FixShardlow::ssa_update(
void FixShardlow::ssa_update_dpd(
int i,
int *jlist,
int jlen,
class RanMars *pRNG
int jlen
)
{
int j,jj,itype,jtype;
double xtmp,ytmp,ztmp,delx,dely,delz;
double delvx,delvy,delvz;
double rsq,r,rinv;
double dot,wd,wr,randnum,factor_dpd,factor_dpd1;
double dpx,dpy,dpz;
double denom, mu_ij;
class RanMars *pRNG;
double **x = atom->x;
double **v = atom->v;
double *rmass = atom->rmass;
double *mass = atom->mass;
int *type = atom->type;
int nlocal = atom->nlocal;
int newton_pair = force->newton_pair;
double randPair;
double *uCond = atom->uCond;
double *uMech = atom->uMech;
double *dpdTheta = atom->dpdTheta;
double kappa_ij, alpha_ij, theta_ij, gamma_ij, sigma_ij;
double vxi, vyi, vzi, vxj, vyj, vzj;
double vx0i, vy0i, vz0i, vx0j, vy0j, vz0j;
double dot1, dot2, dot3, dot4;
double mass_i, mass_j;
double massinv_i, massinv_j;
double *cut_i, *cut2_i, *sigma_i;
double theta_i_inv;
double theta_ij_inv;
const double boltz_inv = 1.0/force->boltz;
const double ftm2v = force->ftm2v;
const double dt = update->dt;
xtmp = x[i][0];
ytmp = x[i][1];
ztmp = x[i][2];
const double xtmp = x[i][0];
const double ytmp = x[i][1];
const double ztmp = x[i][2];
// load velocity for i from memory
vxi = v[i][0];
vyi = v[i][1];
vzi = v[i][2];
double vxi = v[i][0];
double vyi = v[i][1];
double vzi = v[i][2];
itype = type[i];
int itype = type[i];
if(pairDPDE){
cut2_i = pairDPDE->cutsq[itype];
cut_i = pairDPDE->cut[itype];
sigma_i = pairDPDE->sigma[itype];
theta_i_inv = 1.0/dpdTheta[i];
} else {
cut2_i = pairDPD->cutsq[itype];
cut_i = pairDPD->cut[itype];
sigma_i = pairDPD->sigma[itype];
theta_ij = pairDPD->temperature; // independent of i,j
}
mass_i = (rmass) ? rmass[i] : mass[itype];
massinv_i = 1.0 / mass_i;
pRNG = pairDPD->random;
cut2_i = pairDPD->cutsq[itype];
cut_i = pairDPD->cut[itype];
sigma_i = pairDPD->sigma[itype];
theta_ij_inv = 1.0/pairDPD->temperature; // independent of i,j
const double mass_i = (rmass) ? rmass[i] : mass[itype];
const double massinv_i = 1.0 / mass_i;
// Loop over Directional Neighbors only
for (jj = 0; jj < jlen; jj++) {
j = jlist[jj];
j &= NEIGHMASK;
jtype = type[j];
for (int jj = 0; jj < jlen; jj++) {
int j = jlist[jj] & NEIGHMASK;
int jtype = type[j];
delx = xtmp - x[j][0];
dely = ytmp - x[j][1];
delz = ztmp - x[j][2];
rsq = delx*delx + dely*dely + delz*delz;
double delx = xtmp - x[j][0];
double dely = ytmp - x[j][1];
double delz = ztmp - x[j][2];
double rsq = delx*delx + dely*dely + delz*delz;
if (rsq < cut2_i[jtype]) {
r = sqrt(rsq);
if (r < EPSILON) continue; // r can be 0.0 in DPD systems
rinv = 1.0/r;
// NOTE: r can be 0.0 in DPD systems, so do EPSILON_SQUARED test
if ((rsq < cut2_i[jtype]) && (rsq >= EPSILON_SQUARED)) {
double r = sqrt(rsq);
double rinv = 1.0/r;
double delx_rinv = delx*rinv;
double dely_rinv = dely*rinv;
double delz_rinv = delz*rinv;
// Keep a copy of the velocities from previous Shardlow step
vx0i = vxi;
vy0i = vyi;
vz0i = vzi;
double wr = 1.0 - r/cut_i[jtype];
double wdt = wr*wr*dt;
vx0j = vxj = v[j][0];
vy0j = vyj = v[j][1];
vz0j = vzj = v[j][2];
double halfsigma_ij = 0.5*sigma_i[jtype];
double halfgamma_ij = halfsigma_ij*halfsigma_ij*boltz_inv*theta_ij_inv;
// Compute the velocity difference between atom i and atom j
delvx = vx0i - vx0j;
delvy = vy0i - vy0j;
delvz = vz0i - vz0j;
double sigmaRand = halfsigma_ij*wr*dtsqrt*ftm2v * pRNG->gaussian();
dot = (delx*delvx + dely*delvy + delz*delvz);
wr = 1.0 - r/cut_i[jtype];
wd = wr*wr;
double mass_j = (rmass) ? rmass[j] : mass[jtype];
double massinv_j = 1.0 / mass_j;
if(pairDPDE){
// Compute the current temperature
theta_ij = 2.0/(theta_i_inv + 1.0/dpdTheta[j]);
} // else theta_ij = pairDPD->temperature;
sigma_ij = sigma_i[jtype];
randnum = pRNG->gaussian();
double gammaFactor = halfgamma_ij*wdt*ftm2v;
double inv_1p_mu_gammaFactor = 1.0/(1.0 + (massinv_i + massinv_j)*gammaFactor);
gamma_ij = sigma_ij*sigma_ij / (2.0*force->boltz*theta_ij);
randPair = sigma_ij*wr*randnum*dtsqrt;
double vxj = v[j][0];
double vyj = v[j][1];
double vzj = v[j][2];
factor_dpd = -dt*gamma_ij*wd*dot*rinv;
factor_dpd += randPair;
factor_dpd *= 0.5;
// Compute the initial velocity difference between atom i and atom j
double delvx = vxi - vxj;
double delvy = vyi - vyj;
double delvz = vzi - vzj;
double dot_rinv = (delx_rinv*delvx + dely_rinv*delvy + delz_rinv*delvz);
// Compute momentum change between t and t+dt
dpx = factor_dpd*delx*rinv;
dpy = factor_dpd*dely*rinv;
dpz = factor_dpd*delz*rinv;
mass_j = (rmass) ? rmass[j] : mass[jtype];
massinv_j = 1.0 / mass_j;
double factorA = sigmaRand - gammaFactor*dot_rinv;
// Update the velocity on i
vxi += dpx*force->ftm2v*massinv_i;
vyi += dpy*force->ftm2v*massinv_i;
vzi += dpz*force->ftm2v*massinv_i;
vxi += delx_rinv*factorA*massinv_i;
vyi += dely_rinv*factorA*massinv_i;
vzi += delz_rinv*factorA*massinv_i;
if (newton_pair || j < nlocal) {
// Update the velocity on j
vxj -= dpx*force->ftm2v*massinv_j;
vyj -= dpy*force->ftm2v*massinv_j;
vzj -= dpz*force->ftm2v*massinv_j;
}
// Update the velocity on j
vxj -= delx_rinv*factorA*massinv_j;
vyj -= dely_rinv*factorA*massinv_j;
vzj -= delz_rinv*factorA*massinv_j;
//ii. Compute the velocity diff
//ii. Compute the new velocity diff
delvx = vxi - vxj;
delvy = vyi - vyj;
delvz = vzi - vzj;
dot_rinv = delx_rinv*delvx + dely_rinv*delvy + delz_rinv*delvz;
dot = delx*delvx + dely*delvy + delz*delvz;
//iii. Compute dpi again
mu_ij = massinv_i + massinv_j;
denom = 1.0 + 0.5*mu_ij*gamma_ij*wd*dt*force->ftm2v;
factor_dpd = -0.5*dt*gamma_ij*wd*force->ftm2v/denom;
factor_dpd1 = factor_dpd*(mu_ij*randPair);
factor_dpd1 += randPair;
factor_dpd1 *= 0.5;
// Compute the momentum change between t and t+dt
dpx = (factor_dpd*dot*rinv/force->ftm2v + factor_dpd1)*delx*rinv;
dpy = (factor_dpd*dot*rinv/force->ftm2v + factor_dpd1)*dely*rinv;
dpz = (factor_dpd*dot*rinv/force->ftm2v + factor_dpd1)*delz*rinv;
// Compute the new momentum change between t and t+dt
double factorB = (sigmaRand - gammaFactor*dot_rinv)*inv_1p_mu_gammaFactor;
// Update the velocity on i
vxi += dpx*force->ftm2v*massinv_i;
vyi += dpy*force->ftm2v*massinv_i;
vzi += dpz*force->ftm2v*massinv_i;
vxi += delx_rinv*factorB*massinv_i;
vyi += dely_rinv*factorB*massinv_i;
vzi += delz_rinv*factorB*massinv_i;
if (newton_pair || j < nlocal) {
// Update the velocity on j
vxj -= dpx*force->ftm2v*massinv_j;
vyj -= dpy*force->ftm2v*massinv_j;
vzj -= dpz*force->ftm2v*massinv_j;
// Store updated velocity for j
v[j][0] = vxj;
v[j][1] = vyj;
v[j][2] = vzj;
}
// Update the velocity on j
vxj -= delx_rinv*factorB*massinv_j;
vyj -= dely_rinv*factorB*massinv_j;
vzj -= delz_rinv*factorB*massinv_j;
if(pairDPDE){
// Compute uCond
randnum = pRNG->gaussian();
kappa_ij = pairDPDE->kappa[itype][jtype];
alpha_ij = sqrt(2.0*force->boltz*kappa_ij);
randPair = alpha_ij*wr*randnum*dtsqrt;
factor_dpd = kappa_ij*(1.0/dpdTheta[i] - 1.0/dpdTheta[j])*wd*dt;
factor_dpd += randPair;
uCond[i] += factor_dpd;
if (newton_pair || j < nlocal) {
uCond[j] -= factor_dpd;
}
// Compute uMech
dot1 = vxi*vxi + vyi*vyi + vzi*vzi;
dot2 = vxj*vxj + vyj*vyj + vzj*vzj;
dot3 = vx0i*vx0i + vy0i*vy0i + vz0i*vz0i;
dot4 = vx0j*vx0j + vy0j*vy0j + vz0j*vz0j;
dot1 = dot1*mass_i;
dot2 = dot2*mass_j;
dot3 = dot3*mass_i;
dot4 = dot4*mass_j;
factor_dpd = 0.25*(dot1+dot2-dot3-dot4)/force->ftm2v;
uMech[i] -= factor_dpd;
if (newton_pair || j < nlocal) {
uMech[j] -= factor_dpd;
}
}
// Store updated velocity for j
v[j][0] = vxj;
v[j][1] = vyj;
v[j][2] = vzj;
}
}
// store updated velocity for i
@ -411,6 +329,170 @@ void FixShardlow::ssa_update(
v[i][2] = vzi;
}
/* ----------------------------------------------------------------------
Perform the stochastic integration and Shardlow update for constant energy
Allow for both per-type and per-atom mass
NOTE: only implemented for orthogonal boxes, not triclinic
------------------------------------------------------------------------- */
void FixShardlow::ssa_update_dpde(
int i,
int *jlist,
int jlen
)
{
class RanMars *pRNG;
double **x = atom->x;
double **v = atom->v;
double *rmass = atom->rmass;
double *mass = atom->mass;
int *type = atom->type;
double *uCond = atom->uCond;
double *uMech = atom->uMech;
double *dpdTheta = atom->dpdTheta;
double *cut_i, *cut2_i, *sigma_i, *kappa_i;
double theta_ij_inv, theta_i_inv;
const double boltz2 = 2.0*force->boltz;
const double boltz_inv = 1.0/force->boltz;
const double ftm2v = force->ftm2v;
const double dt = update->dt;
const double xtmp = x[i][0];
const double ytmp = x[i][1];
const double ztmp = x[i][2];
// load velocity for i from memory
double vxi = v[i][0];
double vyi = v[i][1];
double vzi = v[i][2];
double uMech_i = uMech[i];
double uCond_i = uCond[i];
int itype = type[i];
pRNG = pairDPDE->random;
cut2_i = pairDPDE->cutsq[itype];
cut_i = pairDPDE->cut[itype];
sigma_i = pairDPDE->sigma[itype];
kappa_i = pairDPDE->kappa[itype];
theta_i_inv = 1.0/dpdTheta[i];
const double mass_i = (rmass) ? rmass[i] : mass[itype];
const double massinv_i = 1.0 / mass_i;
const double mass_i_div_neg4_ftm2v = mass_i*(-0.25)/ftm2v;
// Loop over Directional Neighbors only
for (int jj = 0; jj < jlen; jj++) {
int j = jlist[jj] & NEIGHMASK;
int jtype = type[j];
double delx = xtmp - x[j][0];
double dely = ytmp - x[j][1];
double delz = ztmp - x[j][2];
double rsq = delx*delx + dely*dely + delz*delz;
// NOTE: r can be 0.0 in DPD systems, so do EPSILON_SQUARED test
if ((rsq < cut2_i[jtype]) && (rsq >= EPSILON_SQUARED)) {
double r = sqrt(rsq);
double rinv = 1.0/r;
double delx_rinv = delx*rinv;
double dely_rinv = dely*rinv;
double delz_rinv = delz*rinv;
double wr = 1.0 - r/cut_i[jtype];
double wdt = wr*wr*dt;
// Compute the current temperature
double theta_j_inv = 1.0/dpdTheta[j];
theta_ij_inv = 0.5*(theta_i_inv + theta_j_inv);
double halfsigma_ij = 0.5*sigma_i[jtype];
double halfgamma_ij = halfsigma_ij*halfsigma_ij*boltz_inv*theta_ij_inv;
double sigmaRand = halfsigma_ij*wr*dtsqrt*ftm2v * pRNG->gaussian();
double mass_j = (rmass) ? rmass[j] : mass[jtype];
double mass_ij_div_neg4_ftm2v = mass_j*mass_i_div_neg4_ftm2v;
double massinv_j = 1.0 / mass_j;
// Compute uCond
double kappa_ij = kappa_i[jtype];
double alpha_ij = sqrt(boltz2*kappa_ij);
double del_uCond = alpha_ij*wr*dtsqrt * pRNG->gaussian();
del_uCond += kappa_ij*(theta_i_inv - theta_j_inv)*wdt;
uCond[j] -= del_uCond;
uCond_i += del_uCond;
double gammaFactor = halfgamma_ij*wdt*ftm2v;
double inv_1p_mu_gammaFactor = 1.0/(1.0 + (massinv_i + massinv_j)*gammaFactor);
double vxj = v[j][0];
double vyj = v[j][1];
double vzj = v[j][2];
double dot4 = vxj*vxj + vyj*vyj + vzj*vzj;
double dot3 = vxi*vxi + vyi*vyi + vzi*vzi;
// Compute the initial velocity difference between atom i and atom j
double delvx = vxi - vxj;
double delvy = vyi - vyj;
double delvz = vzi - vzj;
double dot_rinv = (delx_rinv*delvx + dely_rinv*delvy + delz_rinv*delvz);
// Compute momentum change between t and t+dt
double factorA = sigmaRand - gammaFactor*dot_rinv;
// Update the velocity on i
vxi += delx_rinv*factorA*massinv_i;
vyi += dely_rinv*factorA*massinv_i;
vzi += delz_rinv*factorA*massinv_i;
// Update the velocity on j
vxj -= delx_rinv*factorA*massinv_j;
vyj -= dely_rinv*factorA*massinv_j;
vzj -= delz_rinv*factorA*massinv_j;
//ii. Compute the new velocity diff
delvx = vxi - vxj;
delvy = vyi - vyj;
delvz = vzi - vzj;
dot_rinv = delx_rinv*delvx + dely_rinv*delvy + delz_rinv*delvz;
// Compute the new momentum change between t and t+dt
double factorB = (sigmaRand - gammaFactor*dot_rinv)*inv_1p_mu_gammaFactor;
// Update the velocity on i
vxi += delx_rinv*factorB*massinv_i;
vyi += dely_rinv*factorB*massinv_i;
vzi += delz_rinv*factorB*massinv_i;
double partial_uMech = (vxi*vxi + vyi*vyi + vzi*vzi - dot3)*massinv_j;
// Update the velocity on j
vxj -= delx_rinv*factorB*massinv_j;
vyj -= dely_rinv*factorB*massinv_j;
vzj -= delz_rinv*factorB*massinv_j;
partial_uMech += (vxj*vxj + vyj*vyj + vzj*vzj - dot4)*massinv_i;
// Store updated velocity for j
v[j][0] = vxj;
v[j][1] = vyj;
v[j][2] = vzj;
// Compute uMech
double del_uMech = partial_uMech*mass_ij_div_neg4_ftm2v;
uMech_i += del_uMech;
uMech[j] += del_uMech;
}
}
// store updated velocity for i
v[i][0] = vxi;
v[i][1] = vyi;
v[i][2] = vzi;
// store updated uMech and uCond for i
uMech[i] = uMech_i;
uCond[i] = uCond_i;
}
void FixShardlow::initial_integrate(int vflag)
{
@ -421,7 +503,7 @@ void FixShardlow::initial_integrate(int vflag)
int nghost = atom->nghost;
int airnum;
class RanMars *pRNG;
const bool useDPDE = (pairDPDE != NULL);
// NOTE: this logic is specific to orthogonal boxes, not triclinic
@ -441,12 +523,6 @@ void FixShardlow::initial_integrate(int vflag)
// Allocate memory for v_t0 to hold the initial velocities for the ghosts
v_t0 = (double (*)[3]) memory->smalloc(sizeof(double)*3*nghost, "FixShardlow:v_t0");
// Define pointers to access the RNG
if(pairDPDE){
pRNG = pairDPDE->random;
} else {
pRNG = pairDPD->random;
}
inum = list->inum;
ilist = list->ilist;
@ -459,7 +535,7 @@ void FixShardlow::initial_integrate(int vflag)
// Communicate the updated velocities to all nodes
comm->forward_comm_fix(this);
if(pairDPDE){
if(useDPDE){
// Zero out the ghosts' uCond & uMech to be used as delta accumulators
memset(&(atom->uCond[nlocal]), 0, sizeof(double)*nghost);
memset(&(atom->uMech[nlocal]), 0, sizeof(double)*nghost);
@ -471,7 +547,10 @@ void FixShardlow::initial_integrate(int vflag)
i = ilist[ii];
int start = (airnum < 2) ? 0 : list->ndxAIR_ssa[i][airnum - 2];
int len = list->ndxAIR_ssa[i][airnum - 1] - start;
if (len > 0) ssa_update(i, &(list->firstneigh[i][start]), len, pRNG);
if (len > 0) {
if (useDPDE) ssa_update_dpde(i, &(list->firstneigh[i][start]), len);
else ssa_update_dpd(i, &(list->firstneigh[i][start]), len);
}
}
// Communicate the ghost deltas to the atom owners

View File

@ -64,8 +64,8 @@ class FixShardlow : public Fix {
double dtsqrt; // = sqrt(update->dt);
int coord2ssaAIR(double *); // map atom coord to an AIR number
void ssa_update(int, int *, int, class RanMars *);
void ssa_update_dpd(int, int *, int); // Constant Temperature
void ssa_update_dpde(int, int *, int); // Constant Energy
};