/*
* Recover the maximizing variables going back through the
* maximizing bucket_tree; the variables are returned as an array
* of markers (non-explanation variables get INVALID_INDEX).
*/
private int[] backward_maximization() {
int i, j;
int bi = bucket_tree.length - 1;
DiscreteFunction back_df;
Bucket b = bucket_tree[bi];
// If there are no explanation variables in the BayesNet, return null
if (b.backward_pointers == null) return (null);
// Initialize the markers for backward pointers with INVALID_INDEX
int backward_markers[] = new int[bn.number_variables()];
for (i = 0; i < backward_markers.length; i++) backward_markers[i] = BayesNet.INVALID_INDEX;
// Initialize the marker for the last bucket
backward_markers[b.variable.get_index()] = (int) (b.backward_pointers.get_value(0) + 0.5);
// Go backwards through the bucket_tree
for (i = (bi - 1); i >= 0; i--) {
if (!bucket_tree[i].is_explanation()) break;
back_df = bucket_tree[i].backward_pointers;
// Skip null pointers (caused by evidence)
if (back_df == null) continue;
// Special treatment for bucket with only one value,
// since it can be a bucket with only the bucket variable left
if (back_df.number_values() == 1) {
backward_markers[bucket_tree[i].variable.get_index()] = (int) (back_df.get_value(0) + 0.5);
continue;
}
// Process the bucket
j = back_df.get_position_from_indexes(bn.get_probability_variables(), backward_markers);
backward_markers[bucket_tree[i].variable.get_index()] = (int) (back_df.get_value(j) + 0.5);
}
return (backward_markers);
}
/*
* Put a DiscreteFunction into the BucketTree beyond the current
* active_bucket. If was_first_variable_cancelled_by_evidence is true,
* then mark the bucket accordingly.
*/
private void insert(DiscreteFunction df, boolean was_first_variable_cancelled_by_evidence) {
int i, index;
Bucket b;
for (i = active_bucket; i < bucket_tree.length; i++) {
index = bucket_tree[i].variable.get_index();
if (df.memberOf(index)) {
bucket_tree[i].discrete_functions.addElement(df);
// If the function is a ProbabilityFunction, store its
// first variable appropriately (assuming for now that
// the first variable is the only possible non-conditioning variable).
if ((df instanceof ProbabilityFunction) && (!was_first_variable_cancelled_by_evidence)) {
bucket_tree[i].non_conditioning_variables.addElement(df.get_variable(0));
}
return;
}
}
}
/** Print method for BucketTree. */
public void print(PrintStream out) {
out.println("BucketTree:" + "\n\tActive Bucket is " + active_bucket + ".");
for (int i = 0; i < bucket_tree.length; i++) bucket_tree[i].print(out);
out.println("Bucket result: ");
unnormalized_result.print(out);
}
