edu.cmu.tetrad.search.CheckKnowledge Maven / Gradle / Ivy

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package edu.cmu.tetrad.search;

import edu.cmu.tetrad.data.Knowledge;
import edu.cmu.tetrad.data.KnowledgeEdge;
import edu.cmu.tetrad.graph.Edge;
import edu.cmu.tetrad.graph.Edges;
import edu.cmu.tetrad.graph.Graph;
import edu.cmu.tetrad.graph.Node;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

/**
 * Identifies violations of knowledge for a given graph. Both forbidden and required knowledge is checked, by separate
 * methods. Sorted lists of edges violating knowledge are returned.
 *
 * @author josephramsey
 * @version $Id: $Id
 */
public class CheckKnowledge {

    /**
     * Private constructor to prevent instantiation.
     */
    private CheckKnowledge() {
    }

    /**
     * Returns a sorted list of edges that violate the given knowledge.
     *
     * @param graph     the graph.
     * @param knowledge the knowledge.
     * @return a sorted list of edges that violate the given knowledge.
     */
    public static List forbiddenViolations(Graph graph, Knowledge knowledge) {
        List forbiddenViolations = new ArrayList<>();

        for (Edge edge : graph.getEdges()) {
            if (edge.isDirected()) {
                Node x = Edges.getDirectedEdgeTail(edge);
                Node y = Edges.getDirectedEdgeHead(edge);

                if (knowledge.isForbidden(x.getName(), y.getName())) {
                    forbiddenViolations.add(edge);
                }
            }
        }

        Collections.sort(forbiddenViolations);

        return forbiddenViolations;
    }

    /**
     * Returns a sorted list of edges that are required by knowledge but which do not appear in the graph.
     *
     * @param graph     the graph.
     * @param knowledge the knowledge.
     * @return a sorted list of edges that are required by knowledge but which do not appear in the graph.
     */
    public static List requiredViolations(Graph graph, Knowledge knowledge) {
        List requiredViolations = new ArrayList<>();

        Iterator knowledgeEdgeIterator = knowledge.requiredEdgesIterator();

        while (knowledgeEdgeIterator.hasNext()) {
            KnowledgeEdge edge = knowledgeEdgeIterator.next();
            Node x = graph.getNode(edge.getFrom());
            Node y = graph.getNode(edge.getTo());

            if (!graph.containsEdge(Edges.directedEdge(x, y))) {
                requiredViolations.add(Edges.directedEdge(x, y));
            }
        }

        Collections.sort(requiredViolations);

        return requiredViolations;
    }
}