1

I have written a program in c# for quick sort using multithreading. but the code has a problem. the array is not sorted properly. i think it is because the parent thread terminates soon before the child threads sort the array. i am attaching the code herewith. kindly help me.any help is highly appreciated. thanks in advance.

Beulah

```
using System;
using System.Threading;
using System.Collections;
namespace QSort
{
/// <summary>
/// Summary description for Class1.
/// </summary>
class Class1
{
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main(string[] args)
{
Class1 class1 = new Class1();
}
//public int[] a = new int[10000000];
//added
private const int MAX=6;
public int[] a = new int[MAX];
public Class1()
{ int choice=1;
while (choice<3)
{
Random random = new Random();
/*for(Int32 i=0;i<10000000;++i)
a[i] = random.Next(100000000);*/
//added
a[0]=20;
a[1]=10;
a[2]=40;
a[3]=30;
a[4]=60;
a[5]=50;
//}added
ArrayList list = new ArrayList();
list.Add(0);
list.Add(a.Length-1);
DateTime startTime = DateTime.Now;
Console.Write("1. SigleThreaded Sort\n2.MultithreadSort\nEnter Choice : ");
choice=Convert.ToInt32(Console.ReadLine());
switch(choice)
{
case 1:
startTime = DateTime.Now;
QSort(0, a.Length-1);
break;
case 2:
//multithreading startTime = DateTime.Now;
QSort(list);
break;
default:
break;
}
if (choice<3)
{
Console.WriteLine("Time Taken to sort "+a.Length.ToString() +" elements = "+(DateTime.Now.Subtract(startTime)).TotalMilliseconds.ToString()+" MilliSeconds");
//added
for (int index=0; index<MAX; index++)
Console.WriteLine(a[index]);
}
}
}
//this works fine
public void QSort( int left, int right )//singlethreaded
{
int pivot, lhold, rhold;
lhold = left;
rhold = right;
pivot = a[left];
while( left < right )
{
while( (a[right] >= pivot) && (left < right) )
{
right--;
}
if( left != right )
{
a[left] = a[right];
left++;
}
while( (a[left] <= pivot) && (left < right) )
{
left++;
}
if( left != right )
{
a[right] = a[left];
right--;
}
}
a[left] = pivot;
pivot = left;
left = lhold;
right = rhold;
if( left < pivot )
{
QSort( left, pivot-1 );
}
if( right > pivot )
{
QSort( pivot+1, right );
}
}
//i have problem in this method
public void QSort(object listObject) //Multithreaded
{
Int32 left = (Int32)((ArrayList)listObject)[0];
Int32 right = (Int32)((ArrayList)listObject)[1];
int pivot, lhold, rhold;
lhold = left;
rhold = right;
pivot = a[left];
lock(a)
{
while( left < right )
{
while( (a[right] >= pivot) && (left < right) )
{
right--;
}
if( left != right )
{
a[left] = a[right];
left++;
}
while( (a[left] <= pivot) && (left < right) )
{
left++;
}
if( left != right )
{
a[right] = a[left];
right--;
}
}
a[left] = pivot;
pivot = left;
left = lhold;
right = rhold;
}
if( left < pivot )
{
ArrayList list = new ArrayList();
list.Add(left);
list.Add(pivot-1);
ThreadPool.QueueUserWorkItem(new WaitCallback(QSort),list);
}
if( right > pivot )
{
ArrayList list = new ArrayList();
list.Add(pivot+1);
list.Add(right);
ThreadPool.QueueUserWorkItem(new WaitCallback(QSort),list);
}
}
}
}
```