/**
* Sorts the operators topologically, i.e. such that operator <var>i</var> in the returned
* ordering has dependencies (i.e. connected {@link InputPort}s) only from operators
* <var>0..i-1</var>.
*/
public Vector<Operator> topologicalSort() {
final Map<Operator, Integer> originalIndices = new HashMap<Operator, Integer>();
for (int i = 0; i < operators.size(); i++) {
originalIndices.put(operators.get(i), i);
}
EdgeCounter counter = new EdgeCounter(operators);
for (Operator child : getOperators()) {
for (OutputPort out : child.getOutputPorts().getAllPorts()) {
InputPort dest = out.getDestination();
if (dest != null) {
counter.incNumEdges(dest.getPorts().getOwner().getOperator());
}
}
}
Vector<Operator> sorted = new Vector<Operator>();
PriorityQueue<Operator> independentOperators =
new PriorityQueue<Operator>(
Math.max(1, operators.size()),
new Comparator<Operator>() {
@Override
public int compare(Operator o1, Operator o2) {
return originalIndices.get(o1) - originalIndices.get(o2);
}
});
independentOperators.addAll(counter.getIndependentOperators());
while (!independentOperators.isEmpty()) {
Operator first = independentOperators.poll();
sorted.add(first);
for (OutputPort out : first.getOutputPorts().getAllPorts()) {
InputPort dest = out.getDestination();
if (dest != null) {
Operator destOp = dest.getPorts().getOwner().getOperator();
if (counter.decNumEdges(destOp) == 0) {
// independentOperators.addFirst(destOp);
independentOperators.add(destOp);
}
}
}
}
return sorted;
}
