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16 package ch.hslu.exercises.sw11.ex1.n41.array.sort;
17
18 import java.util.Arrays;
19 import java.util.concurrent.RecursiveAction;
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23
24 public final class SortTask extends RecursiveAction {
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26 private static final int THRESHOLD = 5;
27 private final int[] array;
28 private final int min;
29 private final int max;
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36 public SortTask(final int[] array) {
37 this(array, 0, array.length);
38 }
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40 private SortTask(final int[] array, final int min, final int max) {
41 this.array = array;
42 this.min = min;
43 this.max = max;
44 }
45
46 @Override
47 protected void compute() {
48 if (max - min < THRESHOLD) {
49 sortSequentially(min, max);
50 } else {
51 final int mid = min + (max - min) / 2;
52 invokeAll(new SortTask(array, min, mid), new SortTask(array, mid, max));
53 merge(min, mid, max);
54 }
55 }
56
57 private void sortSequentially(final int min, final int max) {
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60 InsertionSort.exec(array, min, max);
61 }
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63 private void merge(final int min, final int mid, final int max) {
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65 int[] buf = Arrays.copyOfRange(array, min, mid);
66 int i = 0;
67 int j = min;
68 int k = mid;
69 while (i < buf.length) {
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71
72 if (k == max || buf[i] < array[k]) {
73 array[j] = buf[i];
74 i++;
75 } else {
76 array[j] = array[k];
77 k++;
78 }
79 j++;
80 }
81 }
82 }