90 lines
2.8 KiB
C
90 lines
2.8 KiB
C
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/*
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* =======================================================================================
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*
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* Author: Jan Eitzinger (je), jan.eitzinger@fau.de
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* Copyright (c) 2021 RRZE, University Erlangen-Nuremberg
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*
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* This file is part of MD-Bench.
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*
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* MD-Bench is free software: you can redistribute it and/or modify it
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* under the terms of the GNU Lesser General Public License as published
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* by the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* MD-Bench is distributed in the hope that it will be useful, but WITHOUT ANY
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* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
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* PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
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* details.
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*
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* You should have received a copy of the GNU Lesser General Public License along
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* with MD-Bench. If not, see <https://www.gnu.org/licenses/>.
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* =======================================================================================
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*/
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#include <likwid-marker.h>
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#include <timing.h>
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#include <neighbor.h>
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#include <parameter.h>
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#include <atom.h>
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double computeForce(
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Parameter *param,
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Atom *atom,
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Neighbor *neighbor)
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{
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int Nlocal = atom->Nlocal;
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int* neighs;
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MD_FLOAT cutforcesq = param->cutforce * param->cutforce;
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MD_FLOAT sigma6 = param->sigma6;
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MD_FLOAT epsilon = param->epsilon;
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MD_FLOAT* fx = atom->fx; MD_FLOAT* fy = atom->fy; MD_FLOAT* fz = atom->fz;
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MD_FLOAT S, E;
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S = getTimeStamp();
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for(int i = 0; i < Nlocal; i++) {
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fx[i] = 0.0;
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fy[i] = 0.0;
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fz[i] = 0.0;
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}
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LIKWID_MARKER_START("force");
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#pragma omp parallel for
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for(int i = 0; i < Nlocal; i++) {
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neighs = &neighbor->neighbors[i * neighbor->maxneighs];
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int numneighs = neighbor->numneigh[i];
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MD_FLOAT xtmp = atom_x(i);
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MD_FLOAT ytmp = atom_y(i);
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MD_FLOAT ztmp = atom_z(i);
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MD_FLOAT fix = 0;
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MD_FLOAT fiy = 0;
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MD_FLOAT fiz = 0;
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for(int k = 0; k < numneighs; k++) {
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int j = neighs[k];
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MD_FLOAT delx = xtmp - atom_x(j);
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MD_FLOAT dely = ytmp - atom_y(j);
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MD_FLOAT delz = ztmp - atom_z(j);
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MD_FLOAT rsq = delx * delx + dely * dely + delz * delz;
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if(rsq < cutforcesq) {
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MD_FLOAT sr2 = 1.0 / rsq;
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MD_FLOAT sr6 = sr2 * sr2 * sr2 * sigma6;
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MD_FLOAT force = 48.0 * sr6 * (sr6 - 0.5) * sr2 * epsilon;
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fix += delx * force;
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fiy += dely * force;
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fiz += delz * force;
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}
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}
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fx[i] += fix;
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fy[i] += fiy;
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fz[i] += fiz;
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}
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LIKWID_MARKER_STOP("force");
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E = getTimeStamp();
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return E-S;
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}
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