/** Meek's rule R3. If a--b, a--c, a--d, c-->b, c-->b, then orient a-->b. */
public static boolean meekR3(Graph graph, Knowledge knowledge) {
List<Node> nodes = graph.getNodes();
boolean changed = false;
for (Node a : nodes) {
List<Node> adjacentNodes = graph.getAdjacentNodes(a);
if (adjacentNodes.size() < 3) {
continue;
}
for (Node b : adjacentNodes) {
List<Node> otherAdjacents = new LinkedList<Node>(adjacentNodes);
otherAdjacents.remove(b);
if (!graph.isUndirectedFromTo(a, b)) {
continue;
}
ChoiceGenerator cg = new ChoiceGenerator(otherAdjacents.size(), 2);
int[] combination;
while ((combination = cg.next()) != null) {
Node c = otherAdjacents.get(combination[0]);
Node d = otherAdjacents.get(combination[1]);
if (graph.isAdjacentTo(c, d)) {
continue;
}
if (!graph.isUndirectedFromTo(a, c)) {
continue;
}
if (!graph.isUndirectedFromTo(a, d)) {
continue;
}
if (graph.isDirectedFromTo(c, b) && graph.isDirectedFromTo(d, b)) {
if (isArrowpointAllowed(a, b, knowledge)) {
graph.setEndpoint(a, b, Endpoint.ARROW);
TetradLogger.getInstance()
.edgeOriented(SearchLogUtils.edgeOrientedMsg("Meek R3", graph.getEdge(a, b)));
changed = true;
break;
}
}
}
}
}
return changed;
}
/** If */
public static boolean meekR2(Graph graph, Knowledge knowledge) {
List<Node> nodes = graph.getNodes();
boolean changed = false;
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]);
if (graph.isDirectedFromTo(b, a)
&& graph.isDirectedFromTo(a, c)
&& graph.isUndirectedFromTo(b, c)) {
if (isArrowpointAllowed(b, c, knowledge)) {
graph.setEndpoint(b, c, Endpoint.ARROW);
TetradLogger.getInstance()
.edgeOriented(SearchLogUtils.edgeOrientedMsg("Meek R2", graph.getEdge(b, c)));
}
} else if (graph.isDirectedFromTo(c, a)
&& graph.isDirectedFromTo(a, b)
&& graph.isUndirectedFromTo(c, b)) {
if (isArrowpointAllowed(c, b, knowledge)) {
graph.setEndpoint(c, b, Endpoint.ARROW);
TetradLogger.getInstance()
.edgeOriented(SearchLogUtils.edgeOrientedMsg("Meek R2", graph.getEdge(c, b)));
}
}
}
}
return changed;
}