Reusing "merge" method again and getting a little better results in IMPL_M_1

app/src/main/java/de/uni_marburg/powersort/MSort/IMPL_M_1.java

@@ -54,19 +54,34 @@ public class IMPL_M_1 {
     }
 
 
-    static <T> List<T> merge(List<T> run1, List<T> run2, Comparator<? super T> c) {
+    static <T> T[] merge(T[] run1, T[] run2, Comparator<? super T> c) {
-        List<T> result = new ArrayList<>();
+        /**
-        while (!run1.isEmpty() && !run2.isEmpty()) {
+         * We need this because:
+         * In Java, you cannot create generic arrays directly (can't write new T[size])
+         * The workaround is to create an Object array and cast it to T[]
+         * This casting generates a warning because the compiler can't verify the type safety at runtime due to Java's type erasure
+         * **/
+        @SuppressWarnings("unchecked")
+        T[] result = (T[]) new Object[run1.length + run2.length];
+        int i = 0, j = 0, k = 0;
+
+        while (i < run1.length && j < run2.length) {
             //This comparison only works if the lists are sorted
-            if (c.compare(run1.getFirst(),run2.getFirst()) < 0) {
+            if (c.compare(run1[i], run2[j]) <= 0) {
-                result.add(run1.removeFirst());
+                result[k++] = run1[i++];
             } else {
-                result.add(run2.removeFirst());
+                result[k++] = run2[j++];
             }
         }
         // can be improved by finding out which one is empty and only add the other one
-        result.addAll(run1);
+        // Copy remaining elements
-        result.addAll(run2);
+        while (i < run1.length) {
+            result[k++] = run1[i++];
+        }
+        while (j < run2.length) {
+            result[k++] = run2[j++];
+        }
+
         return result;
     }
 
@@ -87,7 +102,7 @@ public class IMPL_M_1 {
     static <T> void mergeInplace(T[] a, int i, int m, int j, Comparator<? super T> c) {
        // System.out.printf("Merge(%d, %d, %d)%n", i, m, j);
         MERGE_COST += j - i;
-// Create temporary arrays for merging
+       // Create temporary arrays for merging
         @SuppressWarnings("unchecked")
         T[] left = (T[]) new Object[m - i];
         @SuppressWarnings("unchecked")
@@ -98,22 +113,11 @@ public class IMPL_M_1 {
         System.arraycopy(a, m, right, 0, j - m);
 
         // Merge back to original array
-        int k = i, l = 0, r = 0;
+        // Merge the runs
-        while (l < left.length && r < right.length) {
+        T[] merged = merge(left, right, c);
-            if (c.compare(left[l], right[r]) <= 0) {
-                a[k++] = left[l++];
-            } else {
-                a[k++] = right[r++];
-            }
-        }
 
-        // Copy remaining elements
+        //copy back to original array
-        while (l < left.length) {
+        System.arraycopy(merged, 0, a, i,merged.length);
-            a[k++] = left[l++];
-        }
-        while (r < right.length) {
-            a[k++] = right[r++];
-        }
     }
 
 

app/src/main/java/de/uni_marburg/powersort/MSort/IMPL_M_2.java

@@ -79,7 +79,7 @@ public class IMPL_M_2<T>{
      * of the minimum stack length required as a function of the length
      * of the array being sorted and the minimum merge sequence length.
      */
-    private static final int MIN_MERGE = 24;
+    private static final int MIN_MERGE = 32;
 
     /**
      * The array being sorted.

app/src/test/java/de/uni_marburg/powersort/MSort/PowerSortTest.java

@@ -6,6 +6,7 @@ import java.util.List;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
+import de.uni_marburg.powersort.benchmark.NaturalOrder;
 import org.junit.jupiter.api.Test;
 
 import static de.uni_marburg.powersort.MSort.IMPL_M_1.MERGE_COST;
@@ -34,11 +35,11 @@ class PowerSortTest {
 
     @Test
             public void testWithFinnInputList() {
-        List<Integer> numbers = List.of(new Integer[] {24, 25, 26, 27, 28, 21, 22, 23, 18, 19, 20, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 3, 1, 2});
+        //T [] numbers = (new Integer[] {24, 25, 26, 27, 28, 21, 22, 23, 18, 19, 20, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 3, 1, 2});
 
-       // powerSort(numbers);
+        //powerSort(numbers, NaturalOrder.INSTANCE);
         System.out.println("Result: ");
-        System.out.println(new ArrayList<>(List.of(numbers)));
+      //  System.out.println(new ArrayList<>(List.of(numbers)));
 
     }
 }