double SimulationIsingModel::computeEnergy()
{
double e = 0.0;
for (int i=0; i<_n; i++) {
e += 0.5*computePairEnergy(i);
e += computeFieldEnergy(i);
}
return e;
}
double Model::computeEnergy(unsigned int particle, double position[])
#endif
{
// N.B. This method is somewhat redundant since the same functionality
// could be achieved by using a combination of the computeInteractions
// and model specific computePairEnergy methods.
unsigned int cell; // cell index
unsigned int neighbour; // index of neighbouring particle
double energy = 0; // energy counter
// Check all neighbouring cells including same cell.
for (unsigned int i=0;i<cells.getNeighbours();i++)
{
cell = cells[particles[particle].cell].neighbours[i];
// Check all particles within cell.
for (unsigned int j=0;j<cells[cell].tally;j++)
{
neighbour = cells[cell].particles[j];
// Make sure the particles are different.
if (neighbour != particle)
{
// Calculate model specific pair energy.
#ifndef ISOTROPIC
energy += computePairEnergy(particle, position, orientation,
neighbour, &particles[neighbour].position[0],
&particles[neighbour].orientation[0]);
#else
energy += computePairEnergy(particle, position,
neighbour, &particles[neighbour].position[0]);
#endif
// Early exit test for hard core overlaps and large finite energy repulsions.
if (energy > 1e6) return INF;
}
}
}
return energy;
}
unsigned int PatchyDisc::computeInteractions(unsigned int particle,
double position[], double orientation[], unsigned int interactions[])
{
unsigned int cell; // cell index
unsigned int neighbour; // index of neighbouring particle
unsigned int nInteractions = 0; // interaction counter
// Check all neighbouring cells including same cell.
for (unsigned int i=0;i<cells.getNeighbours();i++)
{
cell = cells[particles[particle].cell].neighbours[i];
// Check all particles within cell.
for (unsigned int j=0;j<cells[cell].tally;j++)
{
neighbour = cells[cell].particles[j];
// Make sure the particles are different.
if (neighbour != particle)
{
// Calculate pair energy.
double energy = computePairEnergy(particle, position, orientation,
neighbour, &particles[neighbour].position[0],
&particles[neighbour].orientation[0]);
// Particles interact.
if (energy < 0)
{
if (nInteractions == maxInteractions)
{
std::cerr << "[ERROR] PatchyDisc: Maximum number of interactions exceeded!\n";
exit(EXIT_FAILURE);
}
interactions[nInteractions] = neighbour;
nInteractions++;
}
}
}
}
return nInteractions;
}
double SimulationIsingModel::computeEnergy(int i)
{
return (computePairEnergy(i) + computeFieldEnergy(i));
}
