timing in tests

Signed-off-by: Mark Herwege <[email protected]>

bundles/org.openhab.core/src/test/java/org/openhab/core/util/StatisticsTest.java

@@ -14,6 +14,7 @@
 
 import static org.junit.jupiter.api.Assertions.*;
 
+import java.io.PrintStream;
 import java.math.BigDecimal;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -33,30 +34,57 @@ public class StatisticsTest {
 
     @Test
     public void testQuickSelect() {
-        List<BigDecimal> baseList = new Random().doubles(100, 0, 100).mapToObj(v -> BigDecimal.valueOf(v)).sorted()
-                .toList();
+        List<BigDecimal> randomList = new Random().doubles(100, 0, 100).mapToObj(v -> BigDecimal.valueOf(v)).toList();
+        int iterations = 50;
 
-        int size = baseList.size();
+        int size = randomList.size();
         int k = size / 2; // median
+
+        long startTime = System.nanoTime();
+        List<BigDecimal> baseList = randomList.stream().sorted().toList();
+        long endTime = System.nanoTime();
+        long duration = endTime - startTime;
         int expected = baseList.get(k).intValue();
         int prevExpected = baseList.get(k - 1).intValue();
 
+        long durationNoForcePrevious = 0;
+        long durationForcePrevious = 0;
         // Iterate a few times with reshuffled list to exclude impact of initial ordering
-        for (int i = 0; i < 10; i++) {
+        for (int i = 0; i < iterations; i++) {
             ArrayList<BigDecimal> bdList = new ArrayList<>(baseList);
             Collections.shuffle(bdList);
+            startTime = System.nanoTime();
             BigDecimal bd = Statistics.quickSelect(bdList, 0, size - 1, k, false);
+            endTime = System.nanoTime();
+            durationNoForcePrevious += endTime - startTime;
             assertNotNull(bd);
             int result = bd.intValue();
             assertEquals(expected, result);
 
             bdList = new ArrayList<>(baseList); // recreate as order may have changed
             Collections.shuffle(bdList);
+            startTime = System.nanoTime();
             bd = Statistics.quickSelect(bdList, 0, size - 1, k, true);
+            endTime = System.nanoTime();
+            durationForcePrevious += endTime - startTime;
             assertNotNull(bd);
             result = bd.intValue();
             assertEquals(expected, result);
             assertEquals(prevExpected, bdList.get(k - 1).intValue());
         }
+
+        PrintStream out = System.out;
+        if (out != null) {
+            out.print("List size: ");
+            out.print(size);
+            out.print(", iterations: ");
+            out.println(iterations);
+            out.print("  Stream sort duration (ns): ");
+            out.println(duration);
+            out.print("  Quickselect average duration (ns): ");
+            out.println(durationNoForcePrevious / iterations);
+            out.print("  Quickselect force previous order average duration (ns): ");
+            out.println(durationForcePrevious / iterations);
+        }
     }
 }