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Assignment 05 Java solution
Dear all,
as promised, here is my Java solution (adapted from last year) to assignment 05, which I wanted to show in my tutorial yesterday but couldn’t due to issues with the projector.
Remark: In two places I use Java Streams - they can be used to work with lists, arrays etc. without the need for for-loops etc.
If you have any questions or suggestions, feel free to respond to this thread.
package info.kwarc.teaching.bayes.SS19;
import java.util.ArrayList;
import java.util.Map;
import java.util.stream.Collectors;
import info.kwarc.teaching.bayes.*;
public class MyQuery extends Query {
@Override
public Double query(Network network, Node node, ArrayList<Pair<Node, Boolean>> evidence) {
Map<Node, Boolean> assignments =
evidence.stream().collect(Collectors.toMap(Pair::getLeft, Pair::getRight));
assignments.put(node, true);
double p1 = pquery(network, assignments);
assignments.put(node, false);
double p2 = pquery(network, assignments);
return p1/(p1 + p2);
}
private static Double pquery(Network network, Map<Node, Boolean> assignments) {
for (Node node : network.getNodes()) {
if (!assignments.containsKey(node)) {
assignments.put(node, true);
double prob = pquery(network, assignments);
assignments.put(node, false);
prob += pquery(network, assignments);
assignments.remove(node);
return prob;
}
}
return getFullProbability(network, assignments);
}
private static Double getFullProbability(Network network, Map<Node, Boolean> assignments) {
double probability = 1.0;
for (Node node : network.getNodes()) {
double parent_prob = node.getProb(node.parents
.stream()
.map(assignments::get)
.toArray(Boolean[]::new));
probability *= assignments.get(node) ? parent_prob : 1 - parent_prob;
}
return probability;
}
}