For this Assignment, you will consider the I/O performed in the threaded sort Assignment from Week 2 and how the I/O contributes to the performance of the threaded sort. Applying the principles identified in this weeks reading, along with the concurrency control mechanisms from Week 3, you will revise the threaded sort application in an effort to improve the I/O performance in order to affect an overall performance improvement.

To prepare:

• Evaluate the manner by which the threaded sort application performs I/O to retrieve the data to be sorted.
• Propose a strategy to improve the performance by applying one or more of the principles to improve the efficiency of I/O that were identified in this weeks reading.
• +++++++++++++++Below is my previous code++++++++++++++

public class MergeSort {

// The mergeSort method returns a sorted copy of the

// String objects contained in the String array data.

/**

* Sorts the String objects using the merge sort algorithm.

*

* @param data the String objects to be sorted

* @return the String objects sorted in ascending order

*/

public static String[] mergeSort(String[] data) {

if (data.length > 1) {

String[] left = new String[data.length / 2];

String[] right = new String[data.length - left.length];

System.arraycopy(data, 0, left, 0, left.length);

System.arraycopy(data, left.length, right, 0, right.length);

left = mergeSort(left);

right = mergeSort(right);

return merge(left, right);

}

else {

return data;

}

}

/**

* The merge method accepts two String arrays that are assumed

* to be sorted in ascending order. The method will return a

* sorted array of String objects containing all String objects

* from the two input collections.

*

* @param left a sorted collection of String objects

* @param right a sorted collection of String objects

* @return a sorted collection of String objects

*/

public static String[] merge(String[] left, String[] right) {

String[] data = new String[left.length + right.length];

int lIndex = 0;

int rIndex = 0;

for (int i=0; i

if (lIndex == left.length) {

data[i] = right[rIndex];

rIndex++;

}

else if (rIndex == right.length) {

data[i] = left[lIndex];

lIndex++;

}

else if (left[lIndex].compareTo(right[rIndex]) < 0) {

data[i] = left[lIndex];

lIndex++;

}

else {

data[i] = right[rIndex];

rIndex++;

}

}

return data;

}

}

import java.io.BufferedReader;

import java.io.File;

import java.io.FileReader;

import java.io.IOException;

import java.util.ArrayList;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

public class Sort {

private static final ExecutorService executorService = Executors

.newFixedThreadPool(2);

/**

* You are to implement this method. The method should invoke one or more

* threads to read and sort the data from the collection of Files. The

* method should return a sorted list of all of the String data contained in

* the files.

*

* @param files

* @return

* @throws IOException

*/

public static String[] threadedSort(File[] files) throws IOException {

for (final File file : files) {

executorService.execute(new SortThread(file));

}

executorService.shutdown();

while(!executorService.isTerminated()){

// do nothing wait for termination

}

return SortThread.sortedData;

}

/**

* Given an array of files, this method will return a sorted list of the

* String data contained in each of the files.

*

* @param files

* the files to be read

* @return the sorted data

* @throws IOException

* thrown if any errors occur reading the file

*/

public static String[] sort(File[] files) throws IOException {

String[] sortedData = new String[0];

for (File file : files) {

String[] data = getData(file);

data = MergeSort.mergeSort(data);

sortedData = MergeSort.merge(sortedData, data);

}

return sortedData;

}

/**

* This method will read in the string data from the specified file and

* return the data as an array of String objects.

*

* @param file

* the file containing the String data

* @return String array containing the String data

* @throws IOException

* thrown if any errors occur reading the file

*/

static String[] getData(File file) throws IOException {

ArrayList data = new ArrayList();

BufferedReader in = new BufferedReader(new FileReader(file));

// Read the data from the file until the end of file is reached

while (true) {

String line = in.readLine();

if (line == null) {

// the end of file was reached

break;

} else {

data.add(line);

}

}

// Close the input stream and return the data

in.close();

return data.toArray(new String[0]);

}

}

import java.io.File;

import java.io.IOException;

public class SortThread implements Runnable {

private final File file;

static String[] sortedData=new String[0];;

public SortThread(File file) {

super();

this.file = file;

}

@Override

public void run() {

String[] data = new String[0];

try {

data = Sort.getData(file);

} catch (IOException e) {

}

data = MergeSort.mergeSort(data);

synchronized (sortedData) {

sortedData = MergeSort.merge(sortedData, data);

}

}

}

import java.io.File;

import java.io.IOException;

/**

* The class SortTest is used to test the threaded and non-threaded

* sort methods. This program will call each method to sort the data

* contained in the four test files. This program will then test the

* results to ensure that the results are sorted in ascending order.

*

* Simply run this program to verify that you have correctly implemented

* the threaded sort method. The program will not verify if your sort

* uses threads, but will verify if your implementation correctly

* sorted the data contained in the four files.

*

* There should be no reason to make modifications to this class.

*/

public class SortTest {

public static void main(String[] args) throws IOException {

File[] files = {new File("enable1.txt"), new File("enable2k.txt"), new File("lower.txt"), new File("mixed.txt")};

// Run Sort.sort on the files

long startTime = System.nanoTime();

String[] sortedData = Sort.sort(files);

long stopTime = System.nanoTime();

double elapsedTime = (stopTime - startTime) / 1000000000.0;

// Test to ensure the data is sorted

for (int i=0; i

if (sortedData[i].compareTo(sortedData[i+1]) > 0) {

System.out.println("The data returned by Sort.sort is not sorted.");

throw new java.lang.IllegalStateException("The data returned by Sort.sort is not sorted");

}

}

System.out.println("The data returned by Sort.sort is sorted.");

System.out.println("Sort.sort took " + elapsedTime + " seconds to read and sort the data.");

// Run Sort.threadedSort on the files and test to ensure the data is sorted

startTime = System.nanoTime();

String[] threadSortedData = Sort.threadedSort(files);

stopTime = System.nanoTime();

double threadedElapsedTime = (stopTime - startTime)/ 1000000000.0;

// Test to ensure the data is sorted

if (sortedData.length != threadSortedData.length) {

System.out.println("The data return by Sort.threadedSort is missing data");

throw new java.lang.IllegalStateException("The data returned by Sort.threadedSort is not sorted");

}

for (int i=0; i

if (threadSortedData[i].compareTo(threadSortedData[i+1]) > 0) {

System.out.println("The data return by Sort.threadedSort is not sorted");

throw new java.lang.IllegalStateException("The data returned by Sort.threadedSort is not sorted");

}

}

System.out.println("The data returned by Sort.threadedSort is sorted.");

System.out.println("Sort.threadedSort took " + threadedElapsedTime + " seconds to read and sort the data.");

}

}