code: ///////////////////////////////////////////////////////////////////////////////
  // For information as to what this class does, see the Javadoc, below.       //
  // Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,       //
  // 2007, 2008, 2009, 2010, 2014, 2015 by Peter Spirtes, Richard Scheines, Joseph   //
  // Ramsey, and Clark Glymour.                                                //
  //                                                                           //
  // This program is free software; you can redistribute it and/or modify      //
  // it under the terms of the GNU General Public License as published by      //
  // the Free Software Foundation; either version 2 of the License, or         //
  // (at your option) any later version.                                       //
  //                                                                           //
  // This program is distributed in the hope that it will be useful,           //
  // but WITHOUT ANY WARRANTY; without even the implied warranty of            //
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the             //
  // GNU General Public License for more details.                              //
  //                                                                           //
  // You should have received a copy of the GNU General Public License         //
  // along with this program; if not, write to the Free Software               //
  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA //
  ///////////////////////////////////////////////////////////////////////////////
  
  package edu.cmu.tetrad.search;
  
  import edu.cmu.tetrad.graph.Node;
  
  import java.io.IOException;
  import java.io.ObjectInputStream;
  import java.util.*;
  
  /**
   * This is the same as the usual SepsetMap described below, but also keeps up with the individual sets of conditioning
   * nodes for d-separation relations for use with the Distributed Causal Inference (DCI) algorithm. <p/> <p>Stores a map
   * from pairs of nodes to separating sets--that is, for each unordered pair of nodes {node1, node2} in a graph, stores a
   * set of nodes conditional on which node1 and node2 are independent (where the nodes are considered as variables) or
   * stores null if the pair was not judged to be independent. (Note that if a sepset is non-null and empty, that should
   * means that the compared nodes were found to be independent conditional on the empty set, whereas if a sepset is null,
   * that should mean that no set was found yet conditional on which the compared nodes are independent. So at the end of
   * the search, a null sepset carries different information from an empty sepset.)</p> <p>We cast the variable-like
   * objects to Node to allow them either to be variables explicitly or else to be graph nodes that in some model could be
   * considered as variables. This allows us to use d-separation as a graphical indicator of what independendence in
   * models ideally should be.</p>
   *
   * @author Robert Tillman
   */
  public final class SepsetMapDci {
      static final long serialVersionUID = 23L;
  
      /**
       * @serial
       */
      private Map<Set<Node>, List<Node>> sepsets =
              new HashMap<>();
  
      private Map<Set<Node>, List<List<Node>>> sepsetSets =
              new HashMap<>();
  
      private Map<Node, LinkedHashSet<Node>> parents = new HashMap<>();
  
      //=============================CONSTRUCTORS===========================//
  
      public SepsetMapDci() {
      }
  
      public SepsetMapDci(SepsetMapDci map) {
          this.sepsets = new HashMap<>(map.sepsets);
          this.sepsetSets = new HashMap<>(map.sepsetSets);
      }
  
      /**
       * Generates a simple exemplar of this class to test serialization.
       */
      public static SepsetMap serializableInstance() {
          return new SepsetMap();
      }
  
      //=============================PUBLIC METHODS========================//
  
      /**
       * Sets the sepset for {x, y} to be z. Note that {x, y} is unordered.
       */
      public void set(Node x, Node y, List<Node> z) {
          Set<Node> pair = new HashSet<>(2);
          pair.add(x);
          pair.add(y);
          if (sepsets.get(pair) == null) {
              sepsets.put(pair, z);
          } else {
              List<Node> newSet = new ArrayList<>(sepsets.get(pair));
              newSet.addAll(z);
              sepsets.put(pair, newSet);
          }
          if (sepsetSets.containsKey(pair)) {
              sepsetSets.get(pair).add(new ArrayList<>(z));
          } else {
              List<List<Node>> condSets = new ArrayList<>();
              condSets.add(new ArrayList<>(z));
              sepsetSets.put(pair, condSets);
          }
      }
  
      /**
       * Retrieves the sepset previously set for {x, y}, or null if no such set
       * was previously set.
       */
      public List<Node> get(Node x, Node y) {
          Set<Node> pair = new HashSet<>(2);
          pair.add(x);
          pair.add(y);
          return sepsets.get(pair);
      }
  
      /**
       * Retrieves the set of all condioning sets for {x, y} or null if no such
       * set was ever set
       */
      public List<List<Node>> getSet(Node x, Node y) {
          Set<Node> pair = new HashSet<>(2);
          pair.add(x);
          pair.add(y);
          return sepsetSets.get(pair);
      }
  
      public void set(Node x, LinkedHashSet<Node> z) {
          if (parents.get(x) != null) {
              parents.get(x).addAll(z);
          } else {
              parents.put(x, z);
          }
      }
  
      public LinkedHashSet<Node> get(Node x) {
          return parents.get(x) == null ? new LinkedHashSet<Node>() : parents.get(x);
      }
  
      public Set<Set<Node>> getSeparatedPairs() {
          return sepsets.keySet();
      }
  
      public boolean equals(Object o) {
          if (!(o instanceof SepsetMapDci)) {
              return false;
          }
  
          SepsetMapDci _sepset = (SepsetMapDci) o;
          return sepsets.equals(_sepset.sepsets) && sepsetSets.equals(_sepset.sepsetSets);
      }
  
  
      /**
       * Adds semantic checks to the default deserialization method. This method
       * must have the standard signature for a readObject method, and the body of
       * the method must begin with "s.defaultReadObject();". Other than that, any
       * semantic checks can be specified and do not need to stay the same from
       * version to version. A readObject method of this form may be added to any
       * class, even if Tetrad sessions were previously saved out using a version
       * of the class that didn't include it. (That's what the
       * "s.defaultReadObject();" is for. See J. Bloch, Effective Java, for help.
       *
       * @throws java.io.IOException
       * @throws ClassNotFoundException
       */
      private void readObject(ObjectInputStream s)
              throws IOException, ClassNotFoundException {
          s.defaultReadObject();
  
          if (sepsets == null) {
              throw new NullPointerException();
          }
      }
  
      public int size() {
          return sepsets.keySet().size();
      }
  
      public String toString() {
          return sepsets.toString() + "\n" + sepsetSets.toString();
      }
  }
  
  
  
  
  
  