Fix root-node precision problems

CHANGELOG.md

@@ -15,8 +15,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
   - Fixed tree consistency (nValues) -> verify
   - Fixed bug in qt2.contains()
 - Fixed tree inconsistency after root resizing after insert(). [#42](https://github.com/tzaeschke/tinspin-indexes/issues/42)
-  - CLean up calls to checkMerge() -> call leaf-merge only in leaf!
-  - What is going on with root expansion? Why does it not fail in tests?
+  Essentially, we enforce all radii and thecenter of the root to be a power of two.
+  This should immensely reduce and problems with precision errors. 
   - check qt0
 
 ## [2.1.3] - 2023-11-19

src/main/java/org/tinspin/index/qthypercube2/QNode.java

@@ -433,7 +433,7 @@ void checkNode(QStats s, QNode<T> parent, int depth) {
 		if (parent != null) {
 			if (!QUtil.isNodeEnclosed(center, radius, parent.center, parent.radius*QUtil.EPS_MUL)) {
 				System.out.println("Outer: " + parent.radius + " " + Arrays.toString(parent.center));
-				System.out.println("Child: " + radius + " " + Arrays.toString(center));
+				System.out.println("Child(" + depth + "): " + radius + " " + Arrays.toString(center));
 				for (int d = 0; d < center.length; d++) {
 					double parentMax = parent.center[d] + parent.radius;
 					double childMax = center[d] + radius;

src/main/java/org/tinspin/index/qthypercube2/QuadTreeKD2.java

@@ -108,7 +108,7 @@ public void insert(double[] key, T value) {
 		PointEntry<T> e = new PointEntry<>(key, value);
 		if (root == null) {
 			// We calculate a better radius when adding a second point.
-			root = new QNode<>(key.clone(), INITIAL_RADIUS);
+			root = new QNode<>(normalizeCopy(key), INITIAL_RADIUS);
 		}
 		if (root.getRadius() == INITIAL_RADIUS) {
 			adjustRootSize(key);
@@ -127,15 +127,34 @@ private void adjustRootSize(double[] key) {
 			return;
 		}
 		if (root.getRadius() == INITIAL_RADIUS) {
-			double dist = PointDistance.L2.dist(key, root.getCenter());
-			if (dist > 0) {
-				root.adjustRadius(2 * dist);
+			double dMax = maxOrthoDistance(key, root.getCenter());
+			for (int i = 0; i < root.getValueCount(); i++) {
+				dMax = Math.max(dMax, maxOrthoDistance(root.getValues()[i].point(), root.getCenter()));
+			}
+			double radius = normalize(dMax) * 2;
+			if (radius > 0) {
+				root.adjustRadius(radius);
 			} else if (root.getValueCount() >= maxNodeSize - 1) {
-				// we just set an arbitrary radius here
+				// all entries have (approximately?) the same coordinates. We just set an arbitrary radius here.
 				root.adjustRadius(1000);
 			}
+//			double dist = PointDistance.L2.dist(key, root.getCenter());
+//			if (dist > 0) {
+//				root.adjustRadius(2 * dist);
+//			} else if (root.getValueCount() >= maxNodeSize - 1) {
+//				// we just set an arbitrary radius here
+//				root.adjustRadius(1000);
+//			}
 		}
 	}
+
+	private static double maxOrthoDistance(double[] v1, double[] v2) {
+		double dMax = 0;
+		for (int i = 0; i < v1.length; i++) {
+			dMax = Math.max(dMax, Math.abs(v1[i] - v2[i]));
+		}
+		return dMax;
+	}
 
 	/**
 	 * Check whether a given key exists.
@@ -260,6 +279,20 @@ public T updateIf(double[] oldKey, double[] newKey, Predicate<PointEntry<T>> con
 		return e.value();
 	}
 
+	private static double normalize(double d) {
+		// Set fraction to "0".
+		return Double.longBitsToDouble(Double.doubleToRawLongBits(d) & 0xFFF0_0000_0000_0000L);
+	}
+
+	private static double[] normalizeCopy(double[] d) {
+		double[] d2 = new double[d.length];
+		for (int i = 0; i < d.length; i++) {
+			d2[i] = normalize(d[i]);
+		}
+		// System.out.println("NORM: " + Arrays.toString(d) + " -> " + Arrays.toString(d2));
+		return d2;
+	}
+
 	/**
 	 * Ensure that the tree covers the entry.
 	 * @param e Entry to cover.

src/test/java/org/tinspin/index/test/PointMultimapTest.java

@@ -141,6 +141,10 @@ private void smokeTest(List<Entry> data) {
         for (Entry e : data) {
             tree.insert(e.p, e);
         }
+
+        // Check consistency
+        tree.getStats();
+
         // System.out.println(tree.toStringTree());
         for (Entry e : data) {
             PointIterator<Entry> it = tree.queryExactPoint(e.p);
@@ -167,6 +171,9 @@ private void smokeTest(List<Entry> data) {
             assertEquals(data.size(), nExtent);
         }
 
+        //System.out.println(tree.toStringTree());
+        tree.getStats();
+
         for (Entry e : data) {
             // System.out.println("query: " + Arrays.toString(e.p));
             PointIterator<Entry> iter = tree.query(e.p, e.p);