private void relabelToFront() {
assert (!V.isEmpty()) : "No vertices";
ListIterator<Vertex> iter = V.listIterator();
while (iter.hasNext()) {
Vertex v = iter.next();
// System.out.println("Considering vertex: " + v);
int oldHeight = v.getHeight();
discharge(v);
if (v.getHeight() > oldHeight) {
iter.remove();
V.addFirst(v);
iter = V.listIterator(1);
}
}
}
private void relabel(Vertex u) {
// System.out.println("Relabeling " + u);
assert (u.getExcess() > 0) : "u not overflowing";
List<Vertex> neighbors = u.getNeighbors();
int minHeight = Integer.MAX_VALUE;
for (Vertex v : neighbors) {
int residCapacity = getResidualCapacity(u, v);
assert (residCapacity == 0 || u.getHeight() <= v.getHeight());
if (residCapacity > 0) {
int partnerHeight = v.getHeight();
minHeight = partnerHeight < minHeight ? partnerHeight : minHeight;
}
}
u.setHeight(1 + minHeight);
}
private void discharge(Vertex u) {
// System.out.println("Discharging " + u);
while (u.getExcess() > 0) {
if (u.getCurrNeighbor() >= u.getNumNeighbors()) {
relabel(u);
u.setCurrNeighbor(0);
} else {
Vertex v = u.getNeighbor(u.getCurrNeighbor());
if (getResidualCapacity(u, v) > 0 && u.getHeight() == v.getHeight() + 1) {
push(u, v);
} else {
u.incNextNeighbor();
}
}
}
}
// Push-relabel methods
// Push() pushes flow forwards, or decreases incoming flow
private void push(Vertex u, Vertex v) {
// System.out.println("Pushing from " + u + " to " + v);
int excess = u.getExcess();
int residualCapacity = getResidualCapacity(u, v);
assert (excess > 0) : "Excess <= 0";
assert (residualCapacity > 0) : "Resid capacity <= 0";
assert (u.getHeight() == v.getHeight() + 1) : "Height of u != height of v + 1";
int changeInFlow = excess < residualCapacity ? excess : residualCapacity;
if (flowsForward(u, v)) {
addToFlow(u, v, changeInFlow);
} else {
addToFlow(v, u, -changeInFlow);
}
u.addToExcess(-changeInFlow);
v.addToExcess(changeInFlow);
}