---

degenSynchronousProduct.java

package gov.nasa.arc.ase.util.graph;

import java.io.IOException;
//#ifdef JDK11


//#else JDK11
import java.util.Iterator;
import java.util.List;
//#endif JDK11

public class degenSynchronousProduct {
  public static void dfs(Graph g, Node[][] nodes, int nsets, Node n0, Node n1) {
    Node n = get(g, nodes, n0, n1);

    List t0 = n0.getOutgoingEdges();
    List t1 = n1.getOutgoingEdges();

    for(Iterator i0 = t0.iterator(); i0.hasNext(); ) {
      Edge e0 = (Edge)i0.next();
      Node next0 = e0.getNext();
      Edge theEdge = null;

      boolean found = false;

      for(Iterator i1 = t1.iterator(); i1.hasNext() && !found; ) {
        Edge e1 = (Edge)i1.next();

        if(e1.getBooleanAttribute("else")) {
            if(theEdge == null)
                theEdge = e1;
        } else {
            found = true;
            for(int i = 0; i < nsets; i++) {
                // n1 is the degeneraliser automaton
                // dimitra's code starts here
                int n1id = n1.getIntAttribute("lower_bound");
                
                            
                if (i >= n1id)  // ignore bits before lower bound 
                {
                // dimitra's code ends here 
                boolean b0 = e0.getBooleanAttribute("acc"+i);
                boolean b1 = e1.getBooleanAttribute("acc"+i);

                if(b0 != b1) {
                    found = false;
                    break;
                }
                }
            }
        }

        if(found) theEdge = e1;
      }

      if(theEdge != null) {
        Node next1 = theEdge.getNext();
        boolean newNext = isNew(nodes, next0, next1);
        Node next = get(g, nodes, next0, next1);
        Edge e = new Edge(n, next, e0.getGuard(), theEdge.getAction(), null);

        if(newNext)
            dfs(g, nodes, nsets, next0, next1);
      }
   }
 } 
  private static Node get(Graph g, Node[][] nodes, Node n0, Node n1) {
    if(nodes[n0.getId()][n1.getId()] == null) {
      Node n = new Node(g);
      String label0 = n0.getStringAttribute("label");
      String label1 = n1.getStringAttribute("label");
      if(label0 == null) label0 = Integer.toString(n0.getId());
      if(label1 == null) label1 = Integer.toString(n1.getId());
      n.setStringAttribute(
      "label", 
      label0 + 
      "+" + 
      label1);
      if(n1.getBooleanAttribute("accepting"))
    n.setBooleanAttribute("accepting", true);

      return nodes[n0.getId()][n1.getId()] = n;
    }

    return nodes[n0.getId()][n1.getId()];
  }  
  private static boolean isNew(Node[][] nodes, Node n0, Node n1) {
    return nodes[n0.getId()][n1.getId()] == null;
  }  
  public static void main(String[] args) {
    Graph g0, g1;
    try {
      g0 = Graph.load(args[0]);
      g1 = Graph.load(args[1]);
    } catch(IOException e) {
      System.err.println("Can't load automata");
      System.exit(1);
      return;
    }
    
    Graph g = product(g0, g1);

    g.save();
  }  
  public static Graph product(Graph g0, Graph g1) {
    int nsets = g0.getIntAttribute("nsets");

    if(nsets != g1.getIntAttribute("nsets")) {
      System.err.println("Different number of accepting sets");
      System.exit(1);
    }

    Node[][] nodes;
    Graph g = new Graph();
    g.setStringAttribute("type", "ba");
    g.setStringAttribute("ac", "nodes");

    nodes = new Node[g0.getNodeCount()][g1.getNodeCount()];

    dfs(g, nodes, nsets, g0.getInit(), g1.getInit());

    return g;
  }  
}

---