NPE with getStats() on empty tree (#36)

* Empty tree getStats()
tzaeschke · Jun 22, 2024 · de6a03c · de6a03c
1 parent 04fa75a
commit de6a03c
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- getStats() for empty trees fails. [#36](https://github.com/tzaeschke/phtree/pull/36)
+
 ## 2.8.0 - 2023-07-29
 
 - Proper kNN implementation with MinMaxHeaps [#33](https://github.com/tzaeschke/phtree/pull/33)

diff --git a/src/main/java/ch/ethz/globis/phtree/v13/PhTree13.java b/src/main/java/ch/ethz/globis/phtree/v13/PhTree13.java
@@ -154,6 +154,9 @@ public int size() {
 
 	@Override
 	public PhTreeStats getStats() {
+		if (getRoot() == null) {
+			return new PhTreeStats(DEPTH_64);
+		}
 		return getStats(0, getRoot(), new PhTreeStats(DEPTH_64));
 	}
 

diff --git a/src/main/java/ch/ethz/globis/phtree/v16/PhTree16.java b/src/main/java/ch/ethz/globis/phtree/v16/PhTree16.java
@@ -170,6 +170,9 @@ public int size() {
 
 	@Override
 	public PhTreeStats getStats() {
+		if (getRoot() == null) {
+			return new PhTreeStats(DEPTH_64);
+		}
 		return getStats(0, getRoot(), new PhTreeStats(DEPTH_64));
 	}
 

diff --git a/src/main/java/ch/ethz/globis/phtree/v16hd/PhTree16HD.java b/src/main/java/ch/ethz/globis/phtree/v16hd/PhTree16HD.java
@@ -174,6 +174,9 @@ public int size() {
 
 	@Override
 	public PhTreeStats getStats() {
+		if (getRoot() == null) {
+			return new PhTreeStats(DEPTH_64);
+		}
 		return getStats(0, getRoot(), new PhTreeStats(DEPTH_64));
 	}
 

diff --git a/src/test/java/ch/ethz/globis/phtree/test/TestMultiMapF2.java b/src/test/java/ch/ethz/globis/phtree/test/TestMultiMapF2.java
@@ -12,6 +12,7 @@
 import ch.ethz.globis.phtree.PhTreeMultiMapF2.*;
 import ch.ethz.globis.phtree.util.BitTools;
 import ch.ethz.globis.phtree.util.Bits;
+import ch.ethz.globis.phtree.util.PhTreeStats;
 import org.junit.Test;
 
 import java.util.*;
@@ -121,8 +122,8 @@ public void testCRUD_JDK8() {
                         break;
                     case 1: {
                         final int id2 = id;
-                        assertEquals(id2, (int) idx.computeIfAbsent(v, id2, (v2) -> id2));
-                        assertNull(idx.computeIfAbsent(v, id2, (v2) -> id2));
+                        assertEquals(id2, (int) idx.computeIfAbsent(v, id2, v2 -> id2));
+                        assertNull(idx.computeIfAbsent(v, id2, v2 -> id2));
                         break;
                     }
                     case 2:
@@ -226,15 +227,15 @@ public void testKNN() {
         assertTrue(3 <= result.size());
 
         result = toList(idx.nearestNeighbour(1, 1, 1));
-        assertTrue(1 <= result.size());
+        assertFalse(result.isEmpty());
         check(result.get(0).getKey(), 1, 1);
 
         result = toList(idx.nearestNeighbour(1, 1, 3));
-        assertTrue(1 <= result.size());
+        assertFalse(result.isEmpty());
         check(result.get(0).getKey(), 1, 3);
 
         result = toList(idx.nearestNeighbour(1, 3, 1));
-        assertTrue(1 <= result.size());
+        assertFalse(result.isEmpty());
         check(result.get(0).getKey(), 3, 1);
     }
 
@@ -273,7 +274,7 @@ public void testKnnLarge() {
                     v[j] = R.nextDouble() * MAXV;
                 }
                 list.forEach(xx -> xx.dist = dist(v, xx.key));
-                list.sort((o1, o2) -> Double.compare(o1.dist, o2.dist));
+                list.sort(Comparator.comparingDouble(o -> o.dist));
                 List<PhEntryDistF<Integer>> nnList = toList(q.reset(MIN_RESULT, PhDistanceF.THIS, v));
                 assertFalse("i=" + i + " d=" + d, nnList.isEmpty());
                 for (int x = 0; x < MIN_RESULT; ++x) {
@@ -483,4 +484,17 @@ public EntryDist(double[] key, T v, double dist) {
             this.dist = dist;
         }
     }
+
+    @Test
+    public void testEmptyTreeStats() {
+        testEmptyTreeStats(2);
+        testEmptyTreeStats(60);
+        testEmptyTreeStats(600);
+    }
+
+    private void testEmptyTreeStats(int dim) {
+        PhTreeMultiMapF2<Integer> ind = newTree(dim);
+        PhTreeStats stats = ind.getStats();
+        assertEquals(0, stats.nNodes);
+    }
 }