From 10bdf184913f6343adc72d88a4455c40e24b63b8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?David=20Proch=C3=A1zka?= <david@prochazka.dev>
Date: Wed, 10 Feb 2021 13:58:51 +0100
Subject: [PATCH] ADD: support for different types of distance measurements in
Node
---
src/mhtree/Node.java | 60 ++++++++++++++++++++++++++++++++++++--------
1 file changed, 50 insertions(+), 10 deletions(-)
diff --git a/src/mhtree/Node.java b/src/mhtree/Node.java
index 6f042bf..05344b4 100644
--- a/src/mhtree/Node.java
+++ b/src/mhtree/Node.java
@@ -6,9 +6,8 @@ import messif.buckets.BucketStorageException;
import messif.objects.LocalAbstractObject;
import java.io.Serializable;
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.List;
+import java.util.*;
+import java.util.function.Function;
import java.util.stream.Collectors;
public abstract class Node implements Serializable {
@@ -18,28 +17,37 @@ public abstract class Node implements Serializable {
*/
private static final long serialVersionUID = 420L;
protected final InsertType insertType;
+ private final DistanceMeasure distanceMeasure;
protected HullOptimizedRepresentationV3 hull;
protected Node parent;
- Node(PrecomputedDistances distances, InsertType insertType) {
+ Node(PrecomputedDistances distances, InsertType insertType, DistanceMeasure distanceMeasure) {
this.hull = new HullOptimizedRepresentationV3(distances);
this.hull.build();
this.insertType = insertType;
+ this.distanceMeasure = distanceMeasure;
}
- public static InternalNode createParent(List<Node> nodes, PrecomputedDistances distances, InsertType insertType) {
+ public static InternalNode createParent(List<Node> nodes, PrecomputedDistances distances, InsertType insertType, DistanceMeasure distanceMeasure) {
List<LocalAbstractObject> objects = nodes.stream()
.map(Node::getObjects)
.flatMap(Collection::stream)
.collect(Collectors.toList());
- return new InternalNode(distances.getSubset(objects), insertType);
+ return new InternalNode(distances.getSubset(objects), insertType, distanceMeasure);
}
- public float getDistance(LocalAbstractObject object) {
- return hull.getHull().stream()
- .map(h -> h.getDistance(object))
- .reduce(Float.MAX_VALUE, Math::min);
+ public double getDistance(LocalAbstractObject object) {
+ switch (distanceMeasure) {
+ case FURTHEST_HULL_OBJECT:
+ return getDistanceToFurthestHullObject(object);
+ case SUM_OF_DISTANCES_TO_HULL_OBJECTS:
+ return getSumOfDistancesToHullObjects(object);
+ case MEDOID:
+ return getDistanceToMedoid(object);
+ default:
+ return getDistanceToNearestHullObject(object);
+ }
}
public boolean isCovered(LocalAbstractObject object) {
@@ -97,4 +105,36 @@ public abstract class Node implements Serializable {
rebuildHull(object);
}
+
+ private double getDistanceToNearestHullObject(LocalAbstractObject object) {
+ return hull.getHull().stream()
+ .mapToDouble(object::getDistance)
+ .min()
+ .orElse(Double.MAX_VALUE);
+ }
+
+ private double getDistanceToFurthestHullObject(LocalAbstractObject object) {
+ return hull.getHull().stream()
+ .mapToDouble(object::getDistance)
+ .max()
+ .orElse(Double.MIN_VALUE);
+ }
+
+ private double getSumOfDistancesToHullObjects(LocalAbstractObject object) {
+ return hull.getHull().stream()
+ .mapToDouble(object::getDistance)
+ .sum();
+ }
+
+ private double getDistanceToMedoid(LocalAbstractObject object) {
+ List<LocalAbstractObject> objects = getObjects();
+ Function<LocalAbstractObject, Double> sumOfDistanceToObject = obj -> objects.stream().mapToDouble(obj::getDistance).sum();
+
+ Map<LocalAbstractObject, Double> objectToObjectDistance = objects.stream()
+ .collect(Collectors.toMap(Function.identity(), sumOfDistanceToObject));
+
+ LocalAbstractObject medoid = Collections.min(objectToObjectDistance.entrySet(), Map.Entry.comparingByValue()).getKey();
+
+ return medoid.getDistance(object);
+ }
}
--
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