/**
* Auxiliary method for cycle detection. Performs a depth-first traversal with vertex markings to
* detect a cycle. If a node with a temporary marking is found, then there is a cycle. Once all
* children of a vertex have been traversed the parent node cannot be part of another cycle and is
* thus permanently marked.
*
* @param jv current job vertex to check
* @param temporarilyMarked set of temporarily marked nodes
* @param permanentlyMarked set of permanently marked nodes
* @return <code>true</code> if there is a cycle, <code>false</code> otherwise
*/
private boolean detectCycle(
final AbstractJobVertex jv,
final HashSet<JobVertexID> temporarilyMarked,
final HashSet<JobVertexID> permanentlyMarked) {
JobVertexID vertexID = jv.getID();
if (permanentlyMarked.contains(vertexID)) {
return false;
} else if (temporarilyMarked.contains(vertexID)) {
return true;
} else {
temporarilyMarked.add(vertexID);
for (int i = 0; i < jv.getNumberOfForwardConnections(); i++) {
if (detectCycle(
jv.getForwardConnection(i).getConnectedVertex(),
temporarilyMarked,
permanentlyMarked)) {
return true;
}
}
permanentlyMarked.add(vertexID);
return false;
}
}
/**
* Auxiliary method to collect all vertices which are reachable from the input vertices.
*
* @param jv the currently considered job vertex
* @param collector a temporary list to store the vertices that have already been visisted
*/
private void collectVertices(
final AbstractJobVertex jv,
final HashSet<JobVertexID> visited,
final List<AbstractJobVertex> collector) {
visited.add(jv.getID());
collector.add(jv);
for (int i = 0; i < jv.getNumberOfForwardConnections(); i++) {
AbstractJobVertex vertex = jv.getForwardConnection(i).getConnectedVertex();
if (!visited.contains(vertex.getID())) {
collectVertices(vertex, visited, collector);
}
}
}