Odd Even Transposition Sort / Brick Sort using pthreads
Odd-Even Transposition Sort is a parallel sorting algorithm. It is based on the Bubble Sort technique, which compares every 2 consecutive numbers in the array and swap them if first is greater than the second to get an ascending order array. It consists of 2 phases – the odd phase and even phase:
- Odd phase: Every odd indexed element is compared with the next even indexed element(considering 1-based indexing).
- Even phase: Every even indexed element is compared with the next odd indexed element.
This article uses the concept of multi-threading, specifically pthread. In each iteration, every pair of 2 consecutive elements is compared using individual threads executing in parallel as illustrated below. Examples:
Input: { 2, 1, 4, 9, 5, 3, 6, 10 }
Output: 1, 2, 3, 4, 5, 6, 9, 10
Input: { 11, 19, 4, 20, 1, 22, 25, 8}
Output: 1, 4, 8, 11, 19, 20, 22, 25
Note: Compile the program using following command on your Linux based system.
g++ program_name.cpp -pthread
Below is the implementation of the above topic:Â
CPP
#include <bits/stdc++.h>
#include <pthread.h>
using namespace std;
#define n 8
int max_threads = (n + 1) / 2;
int a[] = { 2, 1, 4, 9, 5, 3, 6, 10 };
int tmp;
void * compare( void * arg)
{
int index = tmp;
tmp = tmp + 2;
if ((index + 1 < n) && (a[index] > a[index + 1])) {
swap(a[index], a[index + 1]);
}
}
void oddEven(pthread_t threads[])
{
int i, j;
for (i = 1; i <= n; i++) {
if (i % 2 == 1) {
tmp = 0;
for (j = 0; j < max_threads; j++)
pthread_create(&threads[j], NULL, compare, NULL);
for (j = 0; j < max_threads; j++)
pthread_join(threads[j], NULL);
}
else {
tmp = 1;
for (j = 0; j < max_threads - 1; j++)
pthread_create(&threads[j], NULL, compare, NULL);
for (j = 0; j < max_threads - 1; j++)
pthread_join(threads[j], NULL);
}
}
}
void printArray()
{
int i;
for (i = 0; i < n; i++)
cout << a[i] << " " ;
cout << endl;
}
int main()
{
pthread_t threads[max_threads];
cout << "Given array is: " ;
printArray();
oddEven(threads);
cout << "\nSorted array is: " ;
printArray();
return 0;
}
|
Java
import java.util.Arrays;
class OddEvenTranspositionSort {
static final int N = 8 ;
static final int MAX_THREAD = (N + 1 ) / 2 ;
static int [] arr = { 2 , 1 , 4 , 9 , 5 , 3 , 6 , 10 };
static int tmp = 0 ;
static synchronized void compare() {
int index = tmp;
tmp = tmp + 2 ;
if (index + 1 < N && arr[index] > arr[index + 1 ]) {
int temp = arr[index];
arr[index] = arr[index + 1 ];
arr[index + 1 ] = temp;
}
}
static void createThreads() {
Thread[] threads = new Thread[MAX_THREAD];
for ( int index = 0 ; index < MAX_THREAD; index++) {
threads[index] = new Thread(OddEvenTranspositionSort::compare);
threads[index].start();
}
for ( int index = 0 ; index < MAX_THREAD; index++) {
try {
threads[index].join();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
static void oddEven() {
for ( int i = 1 ; i <= N; i++) {
if (i % 2 == 1 ) {
tmp = 0 ;
createThreads();
} else {
tmp = 1 ;
createThreads();
}
}
}
public static void main(String[] args) {
System.out.print( "Given array is: " );
System.out.println(Arrays.toString(arr));
oddEven();
System.out.print( "Sorted array is: " );
System.out.println(Arrays.toString(arr));
}
}
|
Python3
from threading import Thread
N = 8
MAX_THREAD = int ((N + 1 ) / 2 )
arr = [ 2 , 1 , 4 , 9 , 5 , 3 , 6 , 10 ]
tmp = 0
def compare():
global tmp
index = tmp
tmp = tmp + 2
if index + 1 < N and arr[index] > arr[index + 1 ]:
arr[index], arr[index + 1 ] = arr[index + 1 ], arr[index]
def createThreads():
threads = list ( range (MAX_THREAD))
for index in range (MAX_THREAD):
threads[index] = Thread(target = compare)
threads[index].start()
for index in range (MAX_THREAD):
threads[index].join()
def oddEven():
global tmp
for i in range ( 1 , N + 1 ):
if i % 2 :
tmp = 0
createThreads()
else :
tmp = 1
createThreads()
if __name__ = = "__main__" :
print ( "Given array is : %s" % arr)
oddEven()
print ( "Sorted array is : %s" % arr)
|
C#
using System;
using System.Threading;
class OddEvenTranspositionSort
{
const int n = 8;
static int maxThreads = (n + 1) / 2;
static int [] a = { 2, 1, 4, 9, 5, 3, 6, 10 };
static int tmp;
static void Compare( object arg)
{
int index = tmp;
tmp = tmp + 2;
if ((index + 1 < n) && (a[index] > a[index + 1]))
{
int temp = a[index];
a[index] = a[index + 1];
a[index + 1] = temp;
}
}
static void OddEven(Thread[] threads)
{
for ( int i = 1; i <= n; i++)
{
if (i % 2 == 1)
{
tmp = 0;
for ( int j = 0; j < maxThreads; j++)
threads[j] = new Thread(Compare);
for ( int j = 0; j < maxThreads; j++)
threads[j].Start();
for ( int j = 0; j < maxThreads; j++)
threads[j].Join();
}
else
{
tmp = 1;
for ( int j = 0; j < maxThreads - 1; j++)
threads[j] = new Thread(Compare);
for ( int j = 0; j < maxThreads - 1; j++)
threads[j].Start();
for ( int j = 0; j < maxThreads - 1; j++)
threads[j].Join();
}
}
}
static void PrintArray()
{
for ( int i = 0; i < n; i++)
Console.Write(a[i] + " " );
Console.WriteLine();
}
static void Main()
{
Thread[] threads = new Thread[maxThreads];
Console.Write( "Given array is: " );
PrintArray();
OddEven(threads);
Console.Write( "\nSorted array is: " );
PrintArray();
}
}
|
Javascript
const N = 8;
const MAX_THREAD = Math.floor((N + 1) / 2);
const arr = [2, 1, 4, 9, 5, 3, 6, 10];
let tmp = 0;
function compare() {
const index = tmp;
tmp = tmp + 2;
if (index + 1 < N && arr[index] > arr[index + 1]) {
[arr[index], arr[index + 1]] = [arr[index + 1], arr[index]];
}
}
function createThreads() {
const threads = new Array(MAX_THREAD).fill( null );
for (let index = 0; index < MAX_THREAD; index++) {
threads[index] = new Promise(resolve => {
compare();
resolve();
});
}
return Promise.all(threads);
}
function oddEven() {
for (let i = 1; i <= N; i++) {
if (i % 2) {
tmp = 0;
createThreads();
}
else {
tmp = 1;
createThreads();
}
}
}
console.log( "Given array is : " + arr);
oddEven();
console.log( "Sorted array is : " + arr);
|
Output:
Given array is: 2 1 4 9 5 3 6 10
Sorted array is: 1 2 3 4 5 6 9 10
Time complexity: The time complexity is reduced to O(N) due to parallel computation using threads. Work complexity: The work complexity of this program is O(N) as N/2 number of threads(resources) are being used to sort the array. So, the work-time complexity of the program is O(N^2).
Last Updated :
16 Jan, 2024
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