/**
* Performs step C of the algorithm, as indicated on page xxx of CPS, with the modification that
* X--W--Y is oriented as X-->W<--Y if W is *determined by* the sepset of (X, Y), rather than W
* just being *in* the sepset of (X, Y).
*/
public static void pcdOrientC(
SepsetMap set, IndependenceTest test, Knowledge knowledge, Graph graph) {
TetradLogger.getInstance().log("info", "Staring Collider Orientation:");
List<Node> nodes = graph.getNodes();
for (Node y : nodes) {
List<Node> adjacentNodes = graph.getAdjacentNodes(y);
if (adjacentNodes.size() < 2) {
continue;
}
ChoiceGenerator cg = new ChoiceGenerator(adjacentNodes.size(), 2);
int[] combination;
while ((combination = cg.next()) != null) {
Node x = adjacentNodes.get(combination[0]);
Node z = adjacentNodes.get(combination[1]);
// Skip triples that are shielded.
if (graph.isAdjacentTo(x, z)) {
continue;
}
List<Node> sepset = set.get(x, z);
if (sepset == null) {
continue;
}
List<Node> augmentedSet = new LinkedList<Node>(sepset);
augmentedSet.add(y);
if (test.determines(sepset, y)) {
continue;
}
//
if (!test.splitDetermines(sepset, x, z) && test.splitDetermines(augmentedSet, x, z)) {
continue;
}
if (!isArrowpointAllowed(x, y, knowledge) || !isArrowpointAllowed(z, y, knowledge)) {
continue;
}
graph.setEndpoint(x, y, Endpoint.ARROW);
graph.setEndpoint(z, y, Endpoint.ARROW);
TetradLogger.getInstance()
.log("colliderOriented", SearchLogUtils.colliderOrientedMsg(x, y, z));
}
}
TetradLogger.getInstance().log("info", "Finishing Collider Orientation.");
}
/**
* Double checks a sepset map against a pattern to make sure that X is adjacent to Y in the
* pattern iff {X, Y} is not in the domain of the sepset map.
*
* @param sepset a sepset map, over variables V.
* @param pattern a pattern over variables W, V subset of W.
* @return true if the sepset map is consistent with the pattern.
*/
public static boolean verifySepsetIntegrity(SepsetMap sepset, Graph pattern) {
for (Node x : pattern.getNodes()) {
for (Node y : pattern.getNodes()) {
if (x == y) {
continue;
}
if ((pattern.isAdjacentTo(y, x)) != (sepset.get(x, y) == null)) {
System.out.println("Sepset not consistent with graph for {" + x + ", " + y + "}");
return false;
}
}
}
return true;
}
/**
* Step C of PC; orients colliders using specified sepset. That is, orients x *-* y *-* z as x *->
* y <-* z just in case y is in Sepset({x, z}).
*/
public static void orientCollidersUsingSepsets(SepsetMap set, Knowledge knowledge, Graph graph) {
TetradLogger.getInstance().log("info", "Starting Collider Orientation:");
// verifySepsetIntegrity(set, graph);
List<Node> nodes = graph.getNodes();
for (Node a : nodes) {
List<Node> adjacentNodes = graph.getAdjacentNodes(a);
if (adjacentNodes.size() < 2) {
continue;
}
ChoiceGenerator cg = new ChoiceGenerator(adjacentNodes.size(), 2);
int[] combination;
while ((combination = cg.next()) != null) {
Node b = adjacentNodes.get(combination[0]);
Node c = adjacentNodes.get(combination[1]);
// Skip triples that are shielded.
if (graph.isAdjacentTo(b, c)) {
continue;
}
List<Node> sepset = set.get(b, c);
if (sepset != null
&& !sepset.contains(a)
&& isArrowpointAllowed(b, a, knowledge)
&& isArrowpointAllowed(c, a, knowledge)) {
graph.setEndpoint(b, a, Endpoint.ARROW);
graph.setEndpoint(c, a, Endpoint.ARROW);
TetradLogger.getInstance()
.log("colliderOriented", SearchLogUtils.colliderOrientedMsg(b, a, c, sepset));
}
}
}
TetradLogger.getInstance().log("info", "Finishing Collider Orientation.");
}
