Fastest Array sort method =Flashsort?

Question

i'm using Array.sort(object) method to sort the array but the running time is getting slower and slower as the size and number of arrays increase.
As far as i know, Java uses quicksort for Array.sort() and the running time is O(nlogn) with n is the size of the array. Even it's one of the fastest algorithm out there, it will take too long to sort a big number of array.
I heard that flashsort is the fastest algorithm with running time of O(n). This algorithm is by Dr. Karl-Dietrich Neubert's.
Anyone wrote one class already that i can use like Flashsort.sort(array a) ?

Answer 1

There are various implementations of this algorithm on
this page:
http://www.neubert.net/Flacodes/FLACodes.html
I haven't studied it but I had the impression that you
need to assume some things about the input data to get
O(n) time complexity; this isn't the only O(n) sorting
algorithm (radix sort is O(n) too).I think you assume nothing about data. In stead, you need more memory (20%) to sort using FlashSort.
It is kind of memory for speed sorting. Here is the java code by Roseanne Zhang if you are interested:
* FlashSort.java
* Dr. Karl-Dietrich Neubert's Flashsort1 Algorithm
* http://www.neubert.net/Flapaper/9802n.htm
* Translation of algorithm into Java by Roseanne Zhang 
* http://www.webappcabaret.com/javachina
* Timing measurement included
* Full functional application
class FlashSort
    static int   n;
    static int   m;
    static int[] a;
    static int[] l;
     * constructor
     * @param size of the array to be sorted
    public static void flashSort(int size)
        n = size;
        generateRandomArray();
        long start = System.currentTimeMillis();
        partialFlashSort();
        long mid = System.currentTimeMillis();
        insertionSort();
        long end = System.currentTimeMillis();
        // print the time result
        System.out.println("Partial flash sort time     : " + (mid - start) );
        System.out.println("Straight insertion sort time: " + (end - mid) );
     * Entry point
    public static void main(String[] args)
        int size = 0;
        if (args.length == 0)
            usage();
            System.exit(1);
        try
            size = Integer.parseInt(args[0]);
        catch (NumberFormatException nfe) {
            usage();
            System.exit(1);
        FlashSort.flashSort(size);
     * Print usage
    private static void usage()
        System.out.println();
        System.out.println("Usage: java FlashSort n ");
        System.out.println("       n is integer which is the size of array to sort");
     * Generate the random array
    private static void generateRandomArray()
        a = new int[n];
        for (int i=0; i < n; i++)
            a[i] = (int)(Math.random() * 5 * n);
        //printArray(a);
        m = n/20;
        if (m < 30) m = 30;
        l = new int[m];  
     * Partial flash sort
    private static void partialFlashSort()
        int i = 0, j = 0, k = 0;
        int anmin = a[0];
        int nmax  = 0;
        for (i=1; i < n; i++)
            if (a[i] < anmin) anmin=a;
if (a[i] > a[nmax]) nmax=i;
if (anmin == a[nmax]) return;
double c1 = ((double)m - 1)/(a[nmax] - anmin);
for (i=0; i < n; i++)
k=(int)(c1*(a[i] - anmin));
l[k]++;
//printArray(l);
for (k=1; k < m; k++)
l[k] += l[k-1];
int hold = a[nmax];
a[nmax]=a[0];
a[0]=hold;
int nmove = 0;
int flash;
j=0;
k=m-1;
while (nmove < n-1)
while (j > (l[k]-1))
j++;
k = (int)(c1 * (a[j] - anmin));
flash = a[j];
while (!(j == l[k]))
k = (int) (c1 * (flash - anmin));
hold = a[l[k]-1];
a[l[k]-1]=flash;
flash = hold;
l[k]--;
nmove++;
//printArray(a);
* Straight insertion sort
private static void insertionSort()
int i, j, hold;
for (i=a.length-3; i>=0; i--)
if (a[i+1] < a[i])
hold = a[i];
j=i;
while (a[j+1] < hold)
a[j] = a[j+1];
j++;
a[j] = hold;
//printArray(a);
* For checking sorting result and the distribution
private static void printArray(int[] ary)
for (int i=0; i < ary.length; i++) {
if ((i+1)%10 ==0)
System.out.println(ary[i]);
else
System.out.print(ary[i] + " ");
System.out.println();