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dihedral_omp.h
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Sat, Nov 9, 22:44

dihedral_omp.h
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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.
------------------------------------------------------------------------- */
#ifndef LMP_DIHEDRAL_OMP_H
#define LMP_DIHEDRAL_OMP_H
#include "dihedral.h"
#if defined(_OPENMP)
#include <omp.h>
#endif
namespace LAMMPS_NS {
class DihedralOMP : public Dihedral {
protected:
double **virial_thr; // per thread virial
double **eatom_thr; // per thread per atom energy
double ***vatom_thr; // per thread per atom virial
double *energy_thr; // per thread accumlated energy
int maxeatom_thr, maxvatom_thr;
public:
DihedralOMP(class LAMMPS *);
virtual ~DihedralOMP();
virtual double memory_usage();
protected:
double **loop_setup_thr(double **f, int &ifrom, int &ito, int &tid,
const int inum, const int nall, const int nthreads)
{
#if defined(_OPENMP)
if (nthreads > 1) {
tid = omp_get_thread_num();
// each thread works on a fixed chunk of atoms.
const int idelta = 1 + inum/nthreads;
ifrom = tid*idelta;
ito = ifrom + idelta;
if (ito > inum)
ito = inum;
return f + nall*tid;
} else {
#endif
tid = 0;
ifrom = 0;
ito = inum;
return f;
#if defined(_OPENMP)
}
#endif
};
void ev_setup_thr(int, int);
void ev_reduce_thr();
void ev_tally_thr(int, int, int, int, int, int, double,
double *, double *, double *, double, double, double,
double, double, double, double, double, double, int);
// reduce per thread forces into the first part of the force
// array that is used for the non-threaded parts and reset
// the temporary storage to 0.0.
// this is in the header to be inlined.
// need to post a barrier to wait until all threads are done
// with computing forces. the reduction can be threaded as well.
void force_reduce_thr(double **fall, const int nall,
const int nthreads, const int tid)
{
#if defined(_OPENMP)
// NOOP in non-threaded execution.
if (nthreads == 1) return;
#pragma omp barrier
{
double **f;
const int idelta = (nthreads > 1) ? 1 + nall/nthreads : nall;
const int ifrom = tid*idelta;
const int ito = ((ifrom + idelta) > nall) ? nall : (ifrom + idelta);
for (int n = 1; n < nthreads; ++n) {
const int toffs = n*nall;
f = fall + toffs;
for (int m = ifrom; m < ito; ++m) {
fall[m][0] += f[m][0];
f[m][0] = 0.0;
fall[m][1] += f[m][1];
f[m][1] = 0.0;
fall[m][2] += f[m][2];
f[m][2] = 0.0;
}
}
}
#else
// NOOP in non-threaded execution.
return;
#endif
};
};
}
#endif

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