public static PiHelper load_pi_helper(
      PiHelper pi_helper_cache, ConditionalDistribution pxu, Distribution[] pi_messages)
      throws Exception {
    if (pi_messages.length == 0) return new TrivialPiHelper();

    Vector seq = new Vector();
    seq.addElement(pxu.getClass());
    for (int i = 0; i < pi_messages.length; i++) seq.addElement(pi_messages[i].getClass());

    if (pi_helper_cache != null
        && MatchClassPattern.matches(pi_helper_cache.description(), seq, new int[1], new int[1]))
      return pi_helper_cache;

    Class c = find_helper_class(seq, "pi");
    return (PiHelper) c.newInstance();
  }
  /**
   * Check the helpers currently stored in the helper cache to see if any of them can handle the
   * sequence we've just been given. This avoids pinging the belief network context to get a helper
   * list.
   */
  public static Class find_helper_class1(
      Vector seq, String helper_type, int[] max_class_score, int[] max_count_score)
      throws ClassNotFoundException {
    int[] class_score1 = new int[1], count_score1 = new int[1];
    max_class_score[0] = -1;
    max_count_score[0] = -1;
    Class cmax_score = null;

    for (Enumeration e = helper_cache.keys(); e.hasMoreElements(); ) {
      try {
        HelperCacheKey key = (HelperCacheKey) e.nextElement();
        if (!key.helper_type.equals(helper_type)) continue;
        Class c = (Class) helper_cache.get(key);
        SeqTriple[] sm = (SeqTriple[]) invoke_description(c);
        if (sm == null) continue; // apparently not a helper class
        if (MatchClassPattern.matches(sm, seq, class_score1, count_score1)) {
          if (class_score1[0] > max_class_score[0]
              || (class_score1[0] == max_class_score[0] && count_score1[0] > max_count_score[0])) {
            cmax_score = c;
            max_class_score[0] = class_score1[0];
            max_count_score[0] = count_score1[0];
          }
        }
      } catch (Exception e2) {
      } // eat it; stagger forward
    }

    if (Global.debug > 1)
      System.err.println(
          "PiHelperLoader.find_helper_class1: helper "
              + (cmax_score == null ? "is NOT" : "is")
              + " in cache.");
    if (cmax_score == null) // no luck; try to get a helper list from the bnc & plunge ahead
    return find_helper_class0(seq, helper_type, max_class_score, max_count_score);
    else // success!
    return cmax_score;
  }
  /**
   * Contact a belief network context, get the helper list, and search the list to see if there's a
   * helper which matches the type sequence specified. If there's more than one helper which
   * matches, find the ``best fit.''
   *
   * <p>The class and count scores of the best-fitting helper class are written into
   * <tt>max_class_score[0]</tt> and <tt>max_count_score[0]</tt>, respectively.
   */
  public static Class find_helper_class0(
      Vector seq, String helper_type, int[] max_class_score, int[] max_count_score)
      throws ClassNotFoundException {
    long t0 = System.currentTimeMillis();
    if (bnc != null) // make sure the reference is still alive
    try {
        bnc.get_name();
      } catch (RemoteException e) {
        bnc = null;
      }

    if (bnc == null) // need to locate a context
    {
      String cb = System.getProperty("java.rmi.server.codebase", "http://localhost");
      long tt0 = System.currentTimeMillis();
      try {
        bnc = BeliefNetworkContext.locate_context(new URL(cb).getHost());
      } catch (Exception e) {
        throw new ClassNotFoundException("nested: " + e);
      }
    }

    String[] helperlist;
    try {
      helperlist = bnc.get_helper_names(helper_type);
    } catch (RemoteException e) {
      throw new ClassNotFoundException("bnc.get_helper_names failed");
    }

    int[] class_score1 = new int[1], count_score1 = new int[1];
    max_class_score[0] = -1;
    max_count_score[0] = -1;
    Class cmax_score = null;

    for (int i = 0; i < helperlist.length; i++) {
      try {
        Class c = RMIClassLoader.loadClass(helperlist[i]);
        SeqTriple[] sm = (SeqTriple[]) invoke_description(c);
        if (sm == null) continue; // apparently not a helper class
        if (MatchClassPattern.matches(sm, seq, class_score1, count_score1)) {
          if (class_score1[0] > max_class_score[0]
              || (class_score1[0] == max_class_score[0] && count_score1[0] > max_count_score[0])) {
            cmax_score = c;
            max_class_score[0] = class_score1[0];
            max_count_score[0] = count_score1[0];
          }
        }
      } catch (Exception e2) {
        System.err.println("PiHelperLoader: attempt to load " + helperlist[i] + " failed; " + e2);
      }
    }

    if (cmax_score == null) {
      System.err.println("find_helper_class0: failed; helper list:");
      for (int i = 0; i < helperlist.length; i++) System.err.println("\t" + helperlist[i]);

      String s = "";
      for (Enumeration e = seq.elements(); e.hasMoreElements(); ) {
        try {
          Class c = (Class) e.nextElement();
          s += c.getName() + ",";
        } catch (NoSuchElementException ee) {
          s += "???" + ",";
        }
      }

      throw new ClassNotFoundException("no " + helper_type + " helper for sequence [" + s + "]");
    }

    // FOR NOW IGNORE THE POSSIBILITY OF TWO OR MORE MATCHES !!!
    return cmax_score;
  }