FluctuatingChargeObjectiveFunction.cpp

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 *
 * SUPPORT OPEN SCIENCE!  If you use OpenMD or its source code in your
 * research, please cite the following paper when you publish your work:
 *
 * [1] Drisko et al., J. Open Source Softw. 9, 7004 (2024).
 *
 * Good starting points for code and simulation methodology are:
 *
 * [2] Meineke, et al., J. Comp. Chem. 26, 252-271 (2005).
 * [3] Fennell & Gezelter, J. Chem. Phys. 124, 234104 (2006).
 * [4] Sun, Lin & Gezelter, J. Chem. Phys. 128, 234107 (2008).
 * [5] Vardeman, Stocker & Gezelter, J. Chem. Theory Comput. 7, 834 (2011).
 * [6] Kuang & Gezelter, Mol. Phys., 110, 691-701 (2012).
 * [7] Lamichhane, Gezelter & Newman, J. Chem. Phys. 141, 134109 (2014).
 * [8] Bhattarai, Newman & Gezelter, Phys. Rev. B 99, 094106 (2019).
 * [9] Drisko & Gezelter, J. Chem. Theory Comput. 20, 4986-4997 (2024).
 */
 
#include "flucq/FluctuatingChargeObjectiveFunction.hpp"
 
#ifdef IS_MPI
#include <mpi.h>
#endif
 
namespace OpenMD {
 
  FluctuatingChargeObjectiveFunction::FluctuatingChargeObjectiveFunction(
      SimInfo* info, ForceManager* forceMan,
      FluctuatingChargeConstraints* fqConstraints) :
      info_(info),
      forceMan_(forceMan), fqConstraints_(fqConstraints), thermo(info) {}
 
  RealType FluctuatingChargeObjectiveFunction::value(
      const DynamicVector<RealType>& x) {
    setCoor(x);
    forceMan_->calcForces();
    fqConstraints_->applyConstraints();
    return thermo.getPotential();
  }
 
  void FluctuatingChargeObjectiveFunction::gradient(
      DynamicVector<RealType>& grad, const DynamicVector<RealType>& x) {
    setCoor(x);
    forceMan_->calcForces();
    fqConstraints_->applyConstraints();
    getGrad(grad);
  }
 
  RealType FluctuatingChargeObjectiveFunction::valueAndGradient(
      DynamicVector<RealType>& grad, const DynamicVector<RealType>& x) {
    setCoor(x);
    forceMan_->calcForces();
    fqConstraints_->applyConstraints();
    getGrad(grad);
    return thermo.getPotential();
  }
 
  void FluctuatingChargeObjectiveFunction::setCoor(
      const DynamicVector<RealType>& x) const {
    SimInfo::MoleculeIterator i;
    Molecule::FluctuatingChargeIterator j;
    Molecule* mol;
    Atom* atom;
 
    info_->getSnapshotManager()->advance();
 
    int index;
#ifdef IS_MPI
    index = displacements_[myrank_];
#else
    index = 0;
#endif
 
    for (mol = info_->beginMolecule(i); mol != NULL;
         mol = info_->nextMolecule(i)) {
      for (atom = mol->beginFluctuatingCharge(j); atom != NULL;
           atom = mol->nextFluctuatingCharge(j)) {
        atom->setFlucQPos(x[index++]);
      }
    }
  }
 
  void FluctuatingChargeObjectiveFunction::getGrad(
      DynamicVector<RealType>& grad) {
    SimInfo::MoleculeIterator i;
    Molecule::FluctuatingChargeIterator j;
    Molecule* mol;
    Atom* atom;
    grad.setZero();
 
    int index;
#ifdef IS_MPI
    index = displacements_[myrank_];
#else
    index = 0;
#endif
 
    for (mol = info_->beginMolecule(i); mol != NULL;
         mol = info_->nextMolecule(i)) {
      for (atom = mol->beginFluctuatingCharge(j); atom != NULL;
           atom = mol->nextFluctuatingCharge(j)) {
        grad[index++] = -atom->getFlucQFrc();
      }
    }
 
#ifdef IS_MPI
    MPI_Allreduce(MPI_IN_PLACE, &grad[0], nFlucQ_, MPI_REALTYPE, MPI_SUM,
                  MPI_COMM_WORLD);
#endif
  }
 
  DynamicVector<RealType>
      FluctuatingChargeObjectiveFunction::setInitialCoords() {
#ifdef IS_MPI
    MPI_Comm_size(MPI_COMM_WORLD, &nproc_);
    MPI_Comm_rank(MPI_COMM_WORLD, &myrank_);
    std::vector<int> flucqOnProc_(nproc_, 0);
 
    displacements_.clear();
    displacements_.resize(nproc_, 0);
#endif
 
    SimInfo::MoleculeIterator i;
    Molecule::FluctuatingChargeIterator j;
    Molecule* mol;
    Atom* atom;
 
    nFlucQ_ = 0;
 
    for (mol = info_->beginMolecule(i); mol != NULL;
         mol = info_->nextMolecule(i)) {
      for (atom = mol->beginFluctuatingCharge(j); atom != NULL;
           atom = mol->nextFluctuatingCharge(j)) {
        nFlucQ_++;
      }
    }
 
#ifdef IS_MPI
    MPI_Allgather(&nFlucQ_, 1, MPI_INT, &flucqOnProc_[0], 1, MPI_INT,
                  MPI_COMM_WORLD);
 
    nFlucQ_ = 0;
    for (int iproc = 0; iproc < nproc_; iproc++) {
      nFlucQ_ += flucqOnProc_[iproc];
    }
 
    displacements_[0] = 0;
    for (int iproc = 1; iproc < nproc_; iproc++) {
      displacements_[iproc] =
          displacements_[iproc - 1] + flucqOnProc_[iproc - 1];
    }
#endif
 
    DynamicVector<RealType> initCoords(nFlucQ_);
 
    int index;
#ifdef IS_MPI
    index = displacements_[myrank_];
#else
    index = 0;
#endif
 
    for (mol = info_->beginMolecule(i); mol != NULL;
         mol = info_->nextMolecule(i)) {
      for (atom = mol->beginFluctuatingCharge(j); atom != NULL;
           atom = mol->nextFluctuatingCharge(j)) {
        initCoords[index++] = atom->getFlucQPos();
      }
    }
 
#ifdef IS_MPI
    MPI_Allgatherv(MPI_IN_PLACE, 0, MPI_DATATYPE_NULL, &initCoords[0],
                   &flucqOnProc_[0], &displacements_[0], MPI_REALTYPE,
                   MPI_COMM_WORLD);
#endif
 
    return initCoords;
  }
}  // namespace OpenMD