public static boolean meekR1Locally2(
Graph graph, Knowledge knowledge, IndependenceTest test, int depth) {
List<Node> nodes = graph.getNodes();
boolean changed = true;
while (changed) {
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]);
// Skip triples that are shielded.
if (graph.isAdjacentTo(b, c)) {
continue;
}
if (graph.getEndpoint(b, a) == Endpoint.ARROW && graph.isUndirectedFromTo(a, c)) {
if (existsLocalSepsetWithoutDet(b, a, c, test, graph, depth)) {
continue;
}
if (isArrowpointAllowed(a, c, knowledge)) {
graph.setEndpoint(a, c, Endpoint.ARROW);
TetradLogger.getInstance()
.edgeOriented(SearchLogUtils.edgeOrientedMsg("Meek R1", graph.getEdge(a, c)));
changed = true;
}
} else if (graph.getEndpoint(c, a) == Endpoint.ARROW && graph.isUndirectedFromTo(a, b)) {
if (existsLocalSepsetWithoutDet(b, a, c, test, graph, depth)) {
continue;
}
if (isArrowpointAllowed(a, b, knowledge)) {
graph.setEndpoint(a, b, Endpoint.ARROW);
TetradLogger.getInstance()
.edgeOriented(SearchLogUtils.edgeOrientedMsg("Meek R1", graph.getEdge(a, b)));
changed = true;
}
}
}
}
}
return changed;
}
/**
* Helper method. Appears to check if an arrowpoint is permitted by background knowledge.
*
* @param x The possible other node.
* @param y The possible point node.
* @return Whether the arrowpoint is allowed.
*/
private boolean isArrowpointAllowed(Node x, Node y) {
if (graph.getEndpoint(x, y) == Endpoint.ARROW) {
return true;
}
if (graph.getEndpoint(x, y) == Endpoint.TAIL) {
return false;
}
if (graph.getEndpoint(y, x) == Endpoint.ARROW) {
if (!knowledge.isForbidden(x.getName(), y.getName())) return true;
}
if (graph.getEndpoint(y, x) == Endpoint.TAIL) {
if (!knowledge.isForbidden(x.getName(), y.getName())) return true;
}
return graph.getEndpoint(y, x) == Endpoint.CIRCLE;
}