/**
* Generate random molecules
*/
void Linear::generateMolecules(int nMolecule,
DArray<double> exclusionRadius, System& system,
BondPotential *bondPotentialPtr, const Boundary &boundary)
{
int iMol;
// Set up a cell list with twice the maxium exclusion radius as the
// cell size
double maxExclusionRadius = 0.0;
for (int iType = 0; iType < system.simulation().nAtomType(); iType++) {
if (exclusionRadius[iType] > maxExclusionRadius)
maxExclusionRadius = exclusionRadius[iType];
}
// the minimum cell size is twice the maxExclusionRadius,
// but to save memory, we take 2 times that value
CellList cellList;
cellList.allocate(system.simulation().atomCapacity(),
boundary, 2.0*2.0*maxExclusionRadius);
if (nMolecule > capacity())
UTIL_THROW("nMolecule > Species.capacity()!");
Simulation& sim = system.simulation();
for (iMol = 0; iMol < nMolecule; ++iMol) {
// Add a new molecule to the system
Molecule &newMolecule= sim.getMolecule(id());
system.addMolecule(newMolecule);
// Try placing atoms
bool moleculeHasBeenPlaced = false;
for (int iAttempt = 0; iAttempt< maxPlacementAttempts_; iAttempt++) {
// Place first atom
Vector pos;
system.boundary().randomPosition(system.simulation().random(),pos);
Atom &thisAtom = newMolecule.atom(0);
// check if the first atom can be placed at the new position
CellList::NeighborArray neighbors;
cellList.getNeighbors(pos, neighbors);
int nNeighbor = neighbors.size();
bool canBePlaced = true;
for (int j = 0; j < nNeighbor; ++j) {
Atom *jAtomPtr = neighbors[j];
double r = sqrt(system.boundary().distanceSq(
jAtomPtr->position(), pos));
if (r < (exclusionRadius[thisAtom.typeId()] +
exclusionRadius[jAtomPtr->typeId()])) {
canBePlaced = false;
break;
}
}
if (canBePlaced) {
thisAtom.position() = pos;
cellList.addAtom(thisAtom);
// Try to recursively place other atoms
if (tryPlaceAtom(newMolecule, 0, exclusionRadius, system,
cellList, bondPotentialPtr, system.boundary())) {
moleculeHasBeenPlaced = true;
break;
} else {
cellList.deleteAtom(thisAtom);
}
}
}
if (! moleculeHasBeenPlaced) {
std::ostringstream oss;
oss << "Failed to place molecule " << newMolecule.id();
UTIL_THROW(oss.str().c_str());
}
}
#if 0
// Check
for (int iMol =0; iMol < nMolecule; ++iMol) {
Molecule::AtomIterator atomIter;
system.molecule(id(),iMol).begin(atomIter);
for (; atomIter.notEnd(); ++atomIter) {
for (int jMol =0; jMol < nMolecule; ++jMol) {
Molecule::AtomIterator atomIter2;
system.molecule(id(),jMol).begin(atomIter2);
for (; atomIter2.notEnd(); ++atomIter2 ) {
if (atomIter2->id() != atomIter->id()) {
double r = sqrt(boundary.distanceSq(
atomIter->position(),atomIter2->position()));
if (r < (exclusionRadius[atomIter->typeId()]+
exclusionRadius[atomIter2->typeId()])) {
std::cout << r << std::endl;
UTIL_THROW("ERROR");
}
}
}
}
}
}
#endif
}
/*
* Generate, attempt and accept or reject a Hybrid MD/MC move.
*/
bool HybridNphMdMove::move()
{
System::MoleculeIterator molIter;
Molecule::AtomIterator atomIter;
double oldEnergy, newEnergy;
int iSpec;
int nSpec = simulation().nSpecies();
bool accept;
if (nphIntegratorPtr_ == NULL) {
UTIL_THROW("null integrator pointer");
}
// Increment counter for attempted moves
incrementNAttempt();
// Store old boundary lengths.
Vector oldLengths = system().boundary().lengths();
// Store old atom positions in oldPositions_ array.
for (iSpec = 0; iSpec < nSpec; ++iSpec) {
mdSystemPtr_->begin(iSpec, molIter);
for ( ; molIter.notEnd(); ++molIter) {
for (molIter->begin(atomIter); atomIter.notEnd(); ++atomIter) {
oldPositions_[atomIter->id()] = atomIter->position();
}
}
}
// Initialize MdSystem
#ifndef INTER_NOPAIR
mdSystemPtr_->pairPotential().buildPairList();
#endif
mdSystemPtr_->calculateForces();
mdSystemPtr_->setBoltzmannVelocities(energyEnsemble().temperature());
nphIntegratorPtr_->setup();
// generate integrator variables from a Gaussian distribution
Random& random = simulation().random();
double temp = system().energyEnsemble().temperature();
double volume = system().boundary().volume();
if (mode_ == Cubic) {
// one degree of freedom
// barostat_energy = 1/2 (1/W) eta_x^2
double sigma = sqrt(temp/barostatMass_);
nphIntegratorPtr_->setEta(0, sigma*random.gaussian());
} else if (mode_ == Tetragonal) {
// two degrees of freedom
// barostat_energy = 1/2 (1/W) eta_x^2 + 1/2 (1/(2W)) eta_y^2
double sigma1 = sqrt(temp/barostatMass_);
nphIntegratorPtr_->setEta(0, sigma1*random.gaussian());
double sigma2 = sqrt(temp/barostatMass_/2.0);
nphIntegratorPtr_->setEta(1, sigma2*random.gaussian());
} else if (mode_ == Orthorhombic) {
// three degrees of freedom
// barostat_energy = 1/2 (1/W) (eta_x^2 + eta_y^2 + eta_z^2)
double sigma = sqrt(temp/barostatMass_);
nphIntegratorPtr_->setEta(0, sigma*random.gaussian());
nphIntegratorPtr_->setEta(1, sigma*random.gaussian());
nphIntegratorPtr_->setEta(2, sigma*random.gaussian());
}
// Store old energy
oldEnergy = mdSystemPtr_->potentialEnergy();
oldEnergy += mdSystemPtr_->kineticEnergy();
oldEnergy += system().boundaryEnsemble().pressure()*volume;
oldEnergy += nphIntegratorPtr_->barostatEnergy();
// Run a short MD simulation
for (int iStep = 0; iStep < nStep_; ++iStep) {
nphIntegratorPtr_->step();
}
volume = system().boundary().volume();
// Calculate new energy
newEnergy = mdSystemPtr_->potentialEnergy();
newEnergy += mdSystemPtr_->kineticEnergy();
newEnergy += system().boundaryEnsemble().pressure()*volume;
newEnergy += nphIntegratorPtr_->barostatEnergy();
// Decide whether to accept or reject
accept = random.metropolis( boltzmann(newEnergy-oldEnergy) );
// Accept move
if (accept) {
#ifndef INTER_NOPAIR
// Rebuild the McSystem cellList using the new positions.
system().pairPotential().buildCellList();
#endif
// Increment counter for the number of accepted moves.
incrementNAccept();
} else {
// Restore old boundary lengths
system().boundary().setOrthorhombic(oldLengths);
// Restore old atom positions
for (iSpec = 0; iSpec < nSpec; ++iSpec) {
mdSystemPtr_->begin(iSpec, molIter);
for ( ; molIter.notEnd(); ++molIter) {
molIter->begin(atomIter);
for ( ; atomIter.notEnd(); ++atomIter) {
atomIter->position() = oldPositions_[atomIter->id()];
}
}
}
}
return accept;
}
/*
* Generate, attempt and accept or reject a Hybrid MD/MC move.
*/
bool HoomdMove::move()
{
if ((!HoomdIsInitialized_) || moleculeSetHasChanged_) {
initSimulation();
moleculeSetHasChanged_ = false;
}
// We need to create the Integrator every time since we are starting
// with new coordinates, velocities etc.
// this does not seem to incur a significant performance decrease
createIntegrator();
System::MoleculeIterator molIter;
Molecule::AtomIterator atomIter;
int nSpec = simulation().nSpecies();
// Increment counter for attempted moves
incrementNAttempt();
double oldEnergy, newEnergy;
{
// Copy atom coordinates into HOOMD
ArrayHandle<Scalar4> h_pos(particleDataSPtr_->getPositions(), access_location::host, access_mode::readwrite);
ArrayHandle<Scalar4> h_vel(particleDataSPtr_->getVelocities(), access_location::host, access_mode::readwrite);
ArrayHandle<unsigned int> h_tag(particleDataSPtr_->getTags(), access_location::host, access_mode::readwrite);
ArrayHandle<unsigned int> h_rtag(particleDataSPtr_->getRTags(), access_location::host, access_mode::readwrite);
for (int iSpec =0; iSpec < nSpec; ++iSpec) {
system().begin(iSpec, molIter);
for ( ; molIter.notEnd(); ++ molIter) {
for (molIter->begin(atomIter); atomIter.notEnd(); ++atomIter) {
unsigned int idx = (unsigned int) atomIter->id();
Vector& pos = atomIter->position();
h_pos.data[idx].x = pos[0] - lengths_[0]/2.;
h_pos.data[idx].y = pos[1] - lengths_[1]/2.;
h_pos.data[idx].z = pos[2] - lengths_[2]/2.;
int type = atomIter->typeId();
h_vel.data[idx].w = simulation().atomType(type).mass();
h_pos.data[idx].w = __int_as_scalar(type);
h_tag.data[idx] = idx;
h_rtag.data[idx] = idx;
}
}
}
// Generate random velocities
generateRandomVelocities(h_vel);
}
// Notify that the particle order has changed
particleDataSPtr_->notifyParticleSort();
// Initialize integrator (calculate forces and potential energy for step 0)
integratorSPtr_->prepRun(0);
// Calculate oldEnergy
thermoSPtr_->compute(0);
oldEnergy = thermoSPtr_->getLogValue("kinetic_energy",0);
oldEnergy += thermoSPtr_->getLogValue("potential_energy",0);
// Integrate nStep_ steps forward
for (int iStep = 0; iStep < nStep_; ++iStep) {
integratorSPtr_->update(iStep);
// do we need to sort the particles?
// do not sort at time step 0 to speed up short runs
if (! (iStep % sorterPeriod_) && iStep)
sorterSPtr_->update(iStep);
}
// Calculate new energy
thermoSPtr_->compute(nStep_);
newEnergy = thermoSPtr_->getLogValue("kinetic_energy",nStep_);
newEnergy += thermoSPtr_->getLogValue("potential_energy",nStep_);
// Decide whether to accept or reject
bool accept = random().metropolis( boltzmann(newEnergy-oldEnergy) );
if (accept) {
// read back integrated positions
ArrayHandle<Scalar4> h_pos(particleDataSPtr_->getPositions(), access_location::host, access_mode::read);
ArrayHandle<Scalar4> h_vel(particleDataSPtr_->getVelocities(), access_location::host, access_mode::read);
ArrayHandle<unsigned int> h_tag(particleDataSPtr_->getTags(), access_location::host, access_mode::read);
ArrayHandle<unsigned int> h_rtag(particleDataSPtr_->getRTags(), access_location::host, access_mode::read);
for (int iSpec = 0; iSpec < nSpec; ++iSpec) {
system().begin(iSpec, molIter);
for ( ; molIter.notEnd(); ++molIter) {
for (molIter->begin(atomIter); atomIter.notEnd(); ++atomIter) {
unsigned int idx = h_rtag.data[atomIter->id()];
atomIter->position() = Vector(h_pos.data[idx].x+lengths_[0]/2.,
h_pos.data[idx].y+lengths_[1]/2.,
h_pos.data[idx].z+lengths_[2]/2.);
}
}
}
system().pairPotential().buildCellList();
incrementNAccept();
} else {
// not accepted, do nothing
}
return accept;
}
