/**
* Checks to see if there are two neighbors not in same cluster
*
* @param x_i,y_i
*/
public void checkNeighbors(int x_i, int y_i) {
for (int j = 0; j < 4; j++) {
int px = PBC.position(x_i + nnx[j], L);
int py = PBC.position(y_i + nny[j], L);
if ((site[px][py] != -1) && (site[px][py] != site[x_i][y_i])) {
merge(site[px][py], site[x_i][y_i]);
}
}
}
/** Moves a cluster chosen at random in a random direction */
public void step() {
int cluster = (int) (Math.random() * numberOfClusters);
int direction = (int) (Math.random() * 4);
int dx = nnx[direction];
int dy = nny[direction];
int particle = firstParticle[cluster];
do {
site[x[particle]][y[particle]] = -1;
x[particle] = PBC.position(x[particle] + dx, L);
y[particle] = PBC.position(y[particle] + dy, L);
particle = nextParticle[particle];
} while (particle != -1);
particle = firstParticle[cluster];
do {
site[x[particle]][y[particle]] = cluster; // labels new sites occupied by cluster
particle = nextParticle[particle];
} while (particle != -1);
particle = firstParticle[cluster];
do {
checkNeighbors(x[particle], y[particle]); // checks for merger
particle = nextParticle[particle];
} while (particle != -1);
}