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pppm_intel.cpp
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pppm_intel.cpp
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/* ----------------------------------------------------------------------
LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
http://lammps.sandia.gov, Sandia National Laboratories
Steve Plimpton, sjplimp@sandia.gov
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.
------------------------------------------------------------------------- */
/* ----------------------------------------------------------------------
Contributing authors: Rodrigo Canales (RWTH Aachen University)
W. Michael Brown (Intel)
------------------------------------------------------------------------- */
#include <mpi.h>
#include <stdlib.h>
#include <math.h>
#include "pppm_intel.h"
#include "atom.h"
#include "error.h"
#include "gridcomm.h"
#include "math_const.h"
#include "math_special.h"
#include "memory.h"
#include "suffix.h"
using namespace LAMMPS_NS;
using namespace MathConst;
using namespace MathSpecial;
#define MAXORDER 7
#define OFFSET 16384
#define LARGE 10000.0
#define SMALL 0.00001
#define EPS_HOC 1.0e-7
enum{REVERSE_RHO};
enum{FORWARD_IK,FORWARD_AD,FORWARD_IK_PERATOM,FORWARD_AD_PERATOM};
#ifdef FFT_SINGLE
#define ZEROF 0.0f
#define ONEF 1.0f
#else
#define ZEROF 0.0
#define ONEF 1.0
#endif
/* ---------------------------------------------------------------------- */
PPPMIntel::PPPMIntel(LAMMPS *lmp, int narg, char **arg) : PPPM(lmp, narg, arg)
{
suffix_flag |= Suffix::INTEL;
}
PPPMIntel::~PPPMIntel()
{
}
/* ----------------------------------------------------------------------
called once before run
------------------------------------------------------------------------- */
void PPPMIntel::init()
{
PPPM::init();
int ifix = modify->find_fix("package_intel");
if (ifix < 0)
error->all(FLERR,
"The 'package intel' command is required for /intel styles");
fix = static_cast<FixIntel *>(modify->fix[ifix]);
#ifdef _LMP_INTEL_OFFLOAD
_use_base = 0;
if (fix->offload_balance() != 0.0) {
_use_base = 1;
return;
}
#endif
fix->kspace_init_check();
if (order > INTEL_P3M_MAXORDER)
error->all(FLERR,"PPPM order greater than supported by USER-INTEL\n");
/*
if (fix->precision() == FixIntel::PREC_MODE_MIXED)
pack_force_const(force_const_single, fix->get_mixed_buffers());
else if (fix->precision() == FixIntel::PREC_MODE_DOUBLE)
pack_force_const(force_const_double, fix->get_double_buffers());
else
pack_force_const(force_const_single, fix->get_single_buffers());
*/
}
/* ----------------------------------------------------------------------
compute the PPPMIntel long-range force, energy, virial
------------------------------------------------------------------------- */
void PPPMIntel::compute(int eflag, int vflag)
{
#ifdef _LMP_INTEL_OFFLOAD
if (_use_base) {
PPPM::compute(eflag, vflag);
return;
}
#endif
compute_first(eflag,vflag);
compute_second(eflag,vflag);
}
/* ---------------------------------------------------------------------- */
void PPPMIntel::compute_first(int eflag, int vflag)
{
int i,j;
// set energy/virial flags
// invoke allocate_peratom() if needed for first time
if (eflag || vflag) ev_setup(eflag,vflag);
else evflag = evflag_atom = eflag_global = vflag_global =
eflag_atom = vflag_atom = 0;
if (evflag_atom && !peratom_allocate_flag) {
allocate_peratom();
cg_peratom->ghost_notify();
cg_peratom->setup();
}
// if atom count has changed, update qsum and qsqsum
if (atom->natoms != natoms_original) {
qsum_qsq();
natoms_original = atom->natoms;
}
// return if there are no charges
if (qsqsum == 0.0) return;
// convert atoms from box to lamda coords
if (triclinic == 0) boxlo = domain->boxlo;
else {
boxlo = domain->boxlo_lamda;
domain->x2lamda(atom->nlocal);
}
// extend size of per-atom arrays if necessary
if (atom->nmax > nmax) {
memory->destroy(part2grid);
nmax = atom->nmax;
memory->create(part2grid,nmax,3,"pppm:part2grid");
}
// find grid points for all my particles
// map my particle charge onto my local 3d density grid
if (fix->precision() == FixIntel::PREC_MODE_MIXED) {
particle_map<float,double>(fix->get_mixed_buffers());
make_rho<float,double>(fix->get_mixed_buffers());
} else if (fix->precision() == FixIntel::PREC_MODE_DOUBLE) {
particle_map<double,double>(fix->get_double_buffers());
make_rho<double,double>(fix->get_double_buffers());
} else {
particle_map<float,float>(fix->get_single_buffers());
make_rho<float,float>(fix->get_single_buffers());
}
// all procs communicate density values from their ghost cells
// to fully sum contribution in their 3d bricks
// remap from 3d decomposition to FFT decomposition
cg->reverse_comm(this,REVERSE_RHO);
brick2fft();
// compute potential gradient on my FFT grid and
// portion of e_long on this proc's FFT grid
// return gradients (electric fields) in 3d brick decomposition
// also performs per-atom calculations via poisson_peratom()
poisson();
// all procs communicate E-field values
// to fill ghost cells surrounding their 3d bricks
if (differentiation_flag == 1) cg->forward_comm(this,FORWARD_AD);
else cg->forward_comm(this,FORWARD_IK);
// extra per-atom energy/virial communication
if (evflag_atom) {
if (differentiation_flag == 1 && vflag_atom)
cg_peratom->forward_comm(this,FORWARD_AD_PERATOM);
else if (differentiation_flag == 0)
cg_peratom->forward_comm(this,FORWARD_IK_PERATOM);
}
}
/* ---------------------------------------------------------------------- */
void PPPMIntel::compute_second(int eflag, int vflag)
{
int i,j;
// calculate the force on my particles
if (differentiation_flag == 1) {
if (fix->precision() == FixIntel::PREC_MODE_MIXED)
fieldforce_ad<float,double>(fix->get_mixed_buffers());
else if (fix->precision() == FixIntel::PREC_MODE_DOUBLE)
fieldforce_ad<double,double>(fix->get_double_buffers());
else
fieldforce_ad<float,float>(fix->get_single_buffers());
} else {
if (fix->precision() == FixIntel::PREC_MODE_MIXED)
fieldforce_ik<float,double>(fix->get_mixed_buffers());
else if (fix->precision() == FixIntel::PREC_MODE_DOUBLE)
fieldforce_ik<double,double>(fix->get_double_buffers());
else
fieldforce_ik<float,float>(fix->get_single_buffers());
}
// extra per-atom energy/virial communication
if (evflag_atom) fieldforce_peratom();
// sum global energy across procs and add in volume-dependent term
const double qscale = qqrd2e * scale;
if (eflag_global) {
double energy_all;
MPI_Allreduce(&energy,&energy_all,1,MPI_DOUBLE,MPI_SUM,world);
energy = energy_all;
energy *= 0.5*volume;
energy -= g_ewald*qsqsum/MY_PIS +
MY_PI2*qsum*qsum / (g_ewald*g_ewald*volume);
energy *= qscale;
}
// sum global virial across procs
if (vflag_global) {
double virial_all[6];
MPI_Allreduce(virial,virial_all,6,MPI_DOUBLE,MPI_SUM,world);
for (i = 0; i < 6; i++) virial[i] = 0.5*qscale*volume*virial_all[i];
}
// per-atom energy/virial
// energy includes self-energy correction
// ntotal accounts for TIP4P tallying eatom/vatom for ghost atoms
if (evflag_atom) {
double *q = atom->q;
int nlocal = atom->nlocal;
int ntotal = nlocal;
if (tip4pflag) ntotal += atom->nghost;
if (eflag_atom) {
for (i = 0; i < nlocal; i++) {
eatom[i] *= 0.5;
eatom[i] -= g_ewald*q[i]*q[i]/MY_PIS + MY_PI2*q[i]*qsum /
(g_ewald*g_ewald*volume);
eatom[i] *= qscale;
}
for (i = nlocal; i < ntotal; i++) eatom[i] *= 0.5*qscale;
}
if (vflag_atom) {
for (i = 0; i < ntotal; i++)
for (j = 0; j < 6; j++) vatom[i][j] *= 0.5*qscale;
}
}
// 2d slab correction
if (slabflag == 1) slabcorr();
// convert atoms back from lamda to box coords
if (triclinic) domain->lamda2x(atom->nlocal);
}
/* ----------------------------------------------------------------------
find center grid pt for each of my particles
check that full stencil for the particle will fit in my 3d brick
store central grid pt indices in part2grid array
------------------------------------------------------------------------- */
template<class flt_t, class acc_t>
void PPPMIntel::particle_map(IntelBuffers<flt_t,acc_t> *buffers)
{
int nx,ny,nz;
ATOM_T * _noalias const x = buffers->get_x(0);
int nlocal = atom->nlocal;
int flag = 0;
if (!ISFINITE(boxlo[0]) || !ISFINITE(boxlo[1]) || !ISFINITE(boxlo[2]))
error->one(FLERR,"Non-numeric box dimensions - simulation unstable");
const flt_t lo0 = boxlo[0];
const flt_t lo1 = boxlo[1];
const flt_t lo2 = boxlo[2];
const flt_t xi = delxinv;
const flt_t yi = delyinv;
const flt_t zi = delzinv;
const flt_t fshift = shift;
#if defined(LMP_SIMD_COMPILER)
#pragma vector aligned
#pragma simd
#endif
for (int i = 0; i < nlocal; i++) {
// (nx,ny,nz) = global coords of grid pt to "lower left" of charge
// current particle coord can be outside global and local box
// add/subtract OFFSET to avoid int(-0.75) = 0 when want it to be -1
nx = static_cast<int> ((x[i].x-lo0)*xi+fshift) - OFFSET;
ny = static_cast<int> ((x[i].y-lo1)*yi+fshift) - OFFSET;
nz = static_cast<int> ((x[i].z-lo2)*zi+fshift) - OFFSET;
part2grid[i][0] = nx;
part2grid[i][1] = ny;
part2grid[i][2] = nz;
// check that entire stencil around nx,ny,nz will fit in my 3d brick
if (nx+nlower < nxlo_out || nx+nupper > nxhi_out ||
ny+nlower < nylo_out || ny+nupper > nyhi_out ||
nz+nlower < nzlo_out || nz+nupper > nzhi_out)
flag = 1;
}
if (flag) error->one(FLERR,"Out of range atoms - cannot compute PPPM");
}
/* ----------------------------------------------------------------------
create discretized "density" on section of global grid due to my particles
density(x,y,z) = charge "density" at grid points of my 3d brick
(nxlo:nxhi,nylo:nyhi,nzlo:nzhi) is extent of my brick (including ghosts)
in global grid
------------------------------------------------------------------------- */
template<class flt_t, class acc_t>
void PPPMIntel::make_rho(IntelBuffers<flt_t,acc_t> *buffers)
{
// clear 3d density array
memset(&(density_brick[nzlo_out][nylo_out][nxlo_out]),0,
ngrid*sizeof(FFT_SCALAR));
// loop over my charges, add their contribution to nearby grid points
// (nx,ny,nz) = global coords of grid pt to "lower left" of charge
// (dx,dy,dz) = distance to "lower left" grid pt
// (mx,my,mz) = global coords of moving stencil pt
ATOM_T * _noalias const x = buffers->get_x(0);
flt_t * _noalias const q = buffers->get_q(0);
int nlocal = atom->nlocal;
const flt_t lo0 = boxlo[0];
const flt_t lo1 = boxlo[1];
const flt_t lo2 = boxlo[2];
const flt_t xi = delxinv;
const flt_t yi = delyinv;
const flt_t zi = delzinv;
const flt_t fshift = shift;
const flt_t fshiftone = shiftone;
const flt_t fdelvolinv = delvolinv;
for (int i = 0; i < nlocal; i++) {
int nx = part2grid[i][0];
int ny = part2grid[i][1];
int nz = part2grid[i][2];
FFT_SCALAR dx = nx+fshiftone - (x[i].x-lo0)*xi;
FFT_SCALAR dy = ny+fshiftone - (x[i].y-lo1)*yi;
FFT_SCALAR dz = nz+fshiftone - (x[i].z-lo2)*zi;
flt_t rho[3][INTEL_P3M_MAXORDER];
for (int k = nlower; k <= nupper; k++) {
FFT_SCALAR r1,r2,r3;
r1 = r2 = r3 = ZEROF;
for (int l = order-1; l >= 0; l--) {
r1 = rho_coeff[l][k] + r1*dx;
r2 = rho_coeff[l][k] + r2*dy;
r3 = rho_coeff[l][k] + r3*dz;
}
rho[0][k-nlower] = r1;
rho[1][k-nlower] = r2;
rho[2][k-nlower] = r3;
}
FFT_SCALAR z0 = fdelvolinv * q[i];
for (int n = nlower; n <= nupper; n++) {
int mz = n+nz;
FFT_SCALAR y0 = z0*rho[2][n-nlower];
for (int m = nlower; m <= nupper; m++) {
int my = m+ny;
FFT_SCALAR x0 = y0*rho[1][m-nlower];
for (int l = nlower; l <= nupper; l++) {
int mx = l+nx;
density_brick[mz][my][mx] += x0*rho[0][l-nlower];
}
}
}
}
}
/* ----------------------------------------------------------------------
interpolate from grid to get electric field & force on my particles for ik
------------------------------------------------------------------------- */
template<class flt_t, class acc_t>
void PPPMIntel::fieldforce_ik(IntelBuffers<flt_t,acc_t> *buffers)
{
// loop over my charges, interpolate electric field from nearby grid points
// (nx,ny,nz) = global coords of grid pt to "lower left" of charge
// (dx,dy,dz) = distance to "lower left" grid pt
// (mx,my,mz) = global coords of moving stencil pt
// ek = 3 components of E-field on particle
ATOM_T * _noalias const x = buffers->get_x(0);
flt_t * _noalias const q = buffers->get_q(0);
FORCE_T * _noalias const f = buffers->get_f();
int nlocal = atom->nlocal;
const flt_t lo0 = boxlo[0];
const flt_t lo1 = boxlo[1];
const flt_t lo2 = boxlo[2];
const flt_t xi = delxinv;
const flt_t yi = delyinv;
const flt_t zi = delzinv;
const flt_t fshiftone = shiftone;
const flt_t fqqrd2es = qqrd2e * scale;
#if defined(LMP_SIMD_COMPILER)
#pragma vector aligned nontemporal
#pragma simd
#endif
for (int i = 0; i < nlocal; i++) {
int nx = part2grid[i][0];
int ny = part2grid[i][1];
int nz = part2grid[i][2];
FFT_SCALAR dx = nx+fshiftone - (x[i].x-lo0)*xi;
FFT_SCALAR dy = ny+fshiftone - (x[i].y-lo1)*yi;
FFT_SCALAR dz = nz+fshiftone - (x[i].z-lo2)*zi;
flt_t rho[3][INTEL_P3M_MAXORDER];
for (int k = nlower; k <= nupper; k++) {
FFT_SCALAR r1 = rho_coeff[order-1][k];
FFT_SCALAR r2 = rho_coeff[order-1][k];
FFT_SCALAR r3 = rho_coeff[order-1][k];
for (int l = order-2; l >= 0; l--) {
r1 = rho_coeff[l][k] + r1*dx;
r2 = rho_coeff[l][k] + r2*dy;
r3 = rho_coeff[l][k] + r3*dz;
}
rho[0][k-nlower] = r1;
rho[1][k-nlower] = r2;
rho[2][k-nlower] = r3;
}
FFT_SCALAR ekx, eky, ekz;
ekx = eky = ekz = ZEROF;
for (int n = nlower; n <= nupper; n++) {
int mz = n+nz;
FFT_SCALAR z0 = rho[2][n-nlower];
for (int m = nlower; m <= nupper; m++) {
int my = m+ny;
FFT_SCALAR y0 = z0*rho[1][m-nlower];
for (int l = nlower; l <= nupper; l++) {
int mx = l+nx;
FFT_SCALAR x0 = y0*rho[0][l-nlower];
ekx -= x0*vdx_brick[mz][my][mx];
eky -= x0*vdy_brick[mz][my][mx];
ekz -= x0*vdz_brick[mz][my][mx];
}
}
}
// convert E-field to force
const flt_t qfactor = fqqrd2es * q[i];
f[i].x += qfactor*ekx;
f[i].y += qfactor*eky;
if (slabflag != 2) f[i].z += qfactor*ekz;
}
}
/* ----------------------------------------------------------------------
interpolate from grid to get electric field & force on my particles for ad
------------------------------------------------------------------------- */
template<class flt_t, class acc_t>
void PPPMIntel::fieldforce_ad(IntelBuffers<flt_t,acc_t> *buffers)
{
// loop over my charges, interpolate electric field from nearby grid points
// (nx,ny,nz) = global coords of grid pt to "lower left" of charge
// (dx,dy,dz) = distance to "lower left" grid pt
// (mx,my,mz) = global coords of moving stencil pt
// ek = 3 components of E-field on particle
ATOM_T * _noalias const x = buffers->get_x(0);
const flt_t * _noalias const q = buffers->get_q(0);
FORCE_T * _noalias const f = buffers->get_f();
int nlocal = atom->nlocal;
const flt_t ftwo_pi = MY_PI * 2.0;
const flt_t ffour_pi = MY_PI * 4.0;
const flt_t lo0 = boxlo[0];
const flt_t lo1 = boxlo[1];
const flt_t lo2 = boxlo[2];
const flt_t xi = delxinv;
const flt_t yi = delyinv;
const flt_t zi = delzinv;
const flt_t fshiftone = shiftone;
const flt_t fqqrd2es = qqrd2e * scale;
const double *prd = domain->prd;
const double xprd = prd[0];
const double yprd = prd[1];
const double zprd = prd[2];
const flt_t hx_inv = nx_pppm/xprd;
const flt_t hy_inv = ny_pppm/yprd;
const flt_t hz_inv = nz_pppm/zprd;
const flt_t fsf_coeff0 = sf_coeff[0];
const flt_t fsf_coeff1 = sf_coeff[1];
const flt_t fsf_coeff2 = sf_coeff[2];
const flt_t fsf_coeff3 = sf_coeff[3];
const flt_t fsf_coeff4 = sf_coeff[4];
const flt_t fsf_coeff5 = sf_coeff[5];
#if defined(LMP_SIMD_COMPILER)
#pragma vector aligned nontemporal
#pragma simd
#endif
for (int i = 0; i < nlocal; i++) {
int nx = part2grid[i][0];
int ny = part2grid[i][1];
int nz = part2grid[i][2];
FFT_SCALAR dx = nx+fshiftone - (x[i].x-lo0)*xi;
FFT_SCALAR dy = ny+fshiftone - (x[i].y-lo1)*yi;
FFT_SCALAR dz = nz+fshiftone - (x[i].z-lo2)*zi;
flt_t rho[3][INTEL_P3M_MAXORDER];
flt_t drho[3][INTEL_P3M_MAXORDER];
for (int k = nlower; k <= nupper; k++) {
FFT_SCALAR r1,r2,r3,dr1,dr2,dr3;
dr1 = dr2 = dr3 = ZEROF;
r1 = rho_coeff[order-1][k];
r2 = rho_coeff[order-1][k];
r3 = rho_coeff[order-1][k];
for (int l = order-2; l >= 0; l--) {
r1 = rho_coeff[l][k] + r1 * dx;
r2 = rho_coeff[l][k] + r2 * dy;
r3 = rho_coeff[l][k] + r3 * dz;
dr1 = drho_coeff[l][k] + dr1 * dx;
dr2 = drho_coeff[l][k] + dr2 * dy;
dr3 = drho_coeff[l][k] + dr3 * dz;
}
rho[0][k-nlower] = r1;
rho[1][k-nlower] = r2;
rho[2][k-nlower] = r3;
drho[0][k-nlower] = dr1;
drho[1][k-nlower] = dr2;
drho[2][k-nlower] = dr3;
}
FFT_SCALAR ekx, eky, ekz;
ekx = eky = ekz = ZEROF;
for (int n = nlower; n <= nupper; n++) {
int mz = n+nz;
for (int m = nlower; m <= nupper; m++) {
int my = m+ny;
FFT_SCALAR ekx_p = rho[1][m-nlower] * rho[2][n-nlower];
FFT_SCALAR eky_p = drho[1][m-nlower] * rho[2][n-nlower];
FFT_SCALAR ekz_p = rho[1][m-nlower] * drho[2][n-nlower];
for (int l = nlower; l <= nupper; l++) {
int mx = l+nx;
ekx += drho[0][l-nlower] * ekx_p * u_brick[mz][my][mx];
eky += rho[0][l-nlower] * eky_p * u_brick[mz][my][mx];
ekz += rho[0][l-nlower] * ekz_p * u_brick[mz][my][mx];
}
}
}
ekx *= hx_inv;
eky *= hy_inv;
ekz *= hz_inv;
// convert E-field to force
const flt_t qfactor = fqqrd2es * q[i];
const flt_t twoqsq = (flt_t)2.0 * q[i] * q[i];
const flt_t s1 = x[i].x * hx_inv;
const flt_t s2 = x[i].y * hy_inv;
const flt_t s3 = x[i].z * hz_inv;
flt_t sf = fsf_coeff0 * sin(ftwo_pi * s1);
sf += fsf_coeff1 * sin(ffour_pi * s1);
sf *= twoqsq;
f[i].x += qfactor * ekx - fqqrd2es * sf;
sf = fsf_coeff2 * sin(ftwo_pi * s2);
sf += fsf_coeff3 * sin(ffour_pi * s2);
sf *= twoqsq;
f[i].y += qfactor * eky - fqqrd2es * sf;
sf = fsf_coeff4 * sin(ftwo_pi * s3);
sf += fsf_coeff5 * sin(ffour_pi * s3);
sf *= twoqsq;
if (slabflag != 2) f[i].z += qfactor * ekz - fqqrd2es * sf;
}
}
/* ----------------------------------------------------------------------
Pack data into intel package buffers if using LRT mode
------------------------------------------------------------------------- */
void PPPMIntel::pack_buffers()
{
fix->start_watch(TIME_PACK);
#if defined(_OPENMP)
#pragma omp parallel default(none)
#endif
{
int ifrom, ito, tid;
IP_PRE_omp_range_id_align(ifrom, ito, tid, atom->nlocal+atom->nghost,
comm->nthreads,
sizeof(IntelBuffers<float,double>::atom_t));
if (fix->precision() == FixIntel::PREC_MODE_MIXED)
fix->get_mixed_buffers()->thr_pack(ifrom,ito,1);
else if (fix->precision() == FixIntel::PREC_MODE_DOUBLE)
fix->get_double_buffers()->thr_pack(ifrom,ito,1);
else
fix->get_single_buffers()->thr_pack(ifrom,ito,1);
}
fix->stop_watch(TIME_PACK);
}
/* ----------------------------------------------------------------------
Returns 0 if Intel optimizations for PPPM ignored due to offload
------------------------------------------------------------------------- */
#ifdef _LMP_INTEL_OFFLOAD
int PPPMIntel::use_base() {
return _use_base;
}
#endif

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