Created
November 29, 2021 09:40
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Sort million 32-bit integers
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import java.util.Random; | |
import java.util.Arrays; | |
import java.time.*; | |
import java.time.temporal.*; | |
public class MillionDWords { | |
final static int million = 1_000_000; | |
final static int runs = 100; | |
public static void main(String []argc) { | |
int[] numbers = new Random().ints(million, Integer.MIN_VALUE, Integer.MAX_VALUE).toArray(); | |
int[] numbers2 = Arrays.copyOf(numbers, numbers.length); | |
LocalTime initTime = LocalTime.now(); | |
Arrays.sort(numbers); | |
System.out.printf("Arrays.sort() sorted in %10d ns\n", | |
ChronoUnit.NANOS.between(initTime, LocalTime.now())); | |
// System.out.println(Arrays.toString(numbers)); | |
initTime = LocalTime.now(); | |
LSDSort(numbers2); | |
System.out.printf("LSD() sorted in %10d ns\n", | |
ChronoUnit.NANOS.between(initTime, LocalTime.now())); | |
// System.out.println(Arrays.toString(numbers2)); | |
System.out.printf("Arrays are equals: %b\n", | |
Arrays.equals(numbers, numbers2)); | |
} | |
private static int byteAt(int number, int position) { | |
return ((number ^ (1 << (7+8+8+8))) >>> (8 * (3-position))) & 0xFF; | |
} | |
private static void LSDSort(int[] a) { | |
final int N = a.length; | |
final int R = 1<<8; | |
final int W = 4; | |
int[] aux = new int[N]; | |
for (int d = W-1; d >= 0; d--) { | |
int[] count = new int[R+1]; | |
for (int i = 0; i < N; i++) | |
count[byteAt(a[i], d) + 1]++; | |
for (int r = 0; r < R; r++) | |
count[r+1] += count[r]; | |
for (int i = 0; i < N; i++) | |
aux[count[byteAt(a[i], d)]++] = a[i]; | |
for (int i = 0; i < N; i++) | |
a[i] = aux[i]; | |
} | |
} | |
} |
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