396 lines
12 KiB
Java
396 lines
12 KiB
Java
import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.Iterator;
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import java.util.List;
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import java.util.Map;
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import java.io.IOException;
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import java.io.File;
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import java.io.FileReader;
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import java.io.BufferedReader;
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import java.util.Scanner;
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public class MapReduceFiles {
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private static final int LINES_PER_MAP_THREAD = 2000;
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public static void main(String[] args) {
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if (args.length < 3) {
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System.err.println("usage: java MapReduceFiles file1.txt file2.txt file3.txt");
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}
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Map<String, String> input = new HashMap<String, String>();
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try {
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input.put(args[0], readFile(args[0]));
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input.put(args[1], readFile(args[1]));
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input.put(args[2], readFile(args[2]));
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for (String filename : args) {
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input.put(filename, readFile(filename));
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}
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}
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catch (IOException ex)
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{
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System.err.println("Error reading files...\n" + ex.getMessage());
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ex.printStackTrace();
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System.exit(0);
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}
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// APPROACH #1: Brute force
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{
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long startTime = System.currentTimeMillis();
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Map<String, Map<String, Integer>> output = new HashMap<String, Map<String, Integer>>();
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Iterator<Map.Entry<String, String>> inputIter = input.entrySet().iterator();
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while(inputIter.hasNext()) {
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Map.Entry<String, String> entry = inputIter.next();
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String file = entry.getKey();
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String contents = entry.getValue();
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String[] words = contents.trim().split("\\s+");
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for(String word : words) {
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Map<String, Integer> files = output.get(word);
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if (files == null) {
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files = new HashMap<String, Integer>();
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output.put(word, files);
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}
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Integer occurrences = files.remove(file);
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if (occurrences == null) {
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files.put(file, 1);
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} else {
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files.put(file, occurrences.intValue() + 1);
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}
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}
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}
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long timeTaken = System.currentTimeMillis() - startTime;
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System.out.println("Brute Force Results:");
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System.out.println("\tTotal Time: " + timeTaken + "\n");
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}
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// APPROACH #2: MapReduce
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{
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long startTime = System.currentTimeMillis();
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Map<String, Map<String, Integer>> output = new HashMap<String, Map<String, Integer>>();
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// MAP:
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long mapStartTime = System.currentTimeMillis();
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List<MappedItem> mappedItems = new ArrayList<MappedItem>();
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Iterator<Map.Entry<String, String>> inputIter = input.entrySet().iterator();
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while(inputIter.hasNext()) {
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Map.Entry<String, String> entry = inputIter.next();
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String file = entry.getKey();
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String contents = entry.getValue();
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map(file, contents, mappedItems);
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}
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long mapTotalTime = System.currentTimeMillis() - mapStartTime;
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// GROUP:
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long groupStartTime = System.currentTimeMillis();
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Map<String, List<String>> groupedItems = new HashMap<String, List<String>>();
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Iterator<MappedItem> mappedIter = mappedItems.iterator();
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while(mappedIter.hasNext()) {
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MappedItem item = mappedIter.next();
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String word = item.getWord();
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String file = item.getFile();
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List<String> list = groupedItems.get(word);
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if (list == null) {
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list = new ArrayList<String>();
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groupedItems.put(word, list);
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}
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list.add(file);
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}
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long groupTotalTime = System.currentTimeMillis() - groupStartTime;
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// REDUCE:
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long reduceStartTime = System.currentTimeMillis();
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Iterator<Map.Entry<String, List<String>>> groupedIter = groupedItems.entrySet().iterator();
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while(groupedIter.hasNext()) {
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Map.Entry<String, List<String>> entry = groupedIter.next();
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String word = entry.getKey();
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List<String> list = entry.getValue();
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reduce(word, list, output);
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}
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long endTime = System.currentTimeMillis();
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long reduceTotalTime = endTime - reduceStartTime;
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long totalTime = endTime - startTime;
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System.out.println("MapReduce Results:");
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System.out.println("\tMap Time: " + mapTotalTime);
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System.out.println("\tGroup Time: " + groupTotalTime);
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System.out.println("\tReduce Time: " + reduceTotalTime);
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System.out.println("\tTotal Time: " + totalTime + "\n");
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}
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// APPROACH #3: Distributed MapReduce
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{
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long startTime = System.currentTimeMillis();
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final Map<String, Map<String, Integer>> output = new HashMap<String, Map<String, Integer>>();
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// MAP:
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long mapStartTime = System.currentTimeMillis();
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List<MappedItem> mappedItems = new ArrayList<MappedItem>();
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final MapCallback<String, MappedItem> mapCallback = new MapCallback<String, MappedItem>() {
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@Override
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public synchronized void mapDone(String file, List<MappedItem> results) {
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mappedItems.addAll(results);
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}
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};
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List<Thread> mapCluster = new ArrayList<Thread>();
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for (Map.Entry<String, String> entry : input.entrySet()) {
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final String file = entry.getKey();
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final String contents = entry.getValue();
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final String[] lines = contents.split("\\r?\\n");
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for (int i = 0; i < lines.length; i += LINES_PER_MAP_THREAD) {
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int end = Math.min(i + LINES_PER_MAP_THREAD, lines.length);
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final List<String> chunk = new ArrayList<>();
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for (int j = i; j < end; j++) {
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chunk.addAll(splitLongLine(lines[j]));
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}
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Thread t = new Thread(new Runnable() {
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@Override
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public void run() {
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map(file, chunk, mapCallback);
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}
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});
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mapCluster.add(t);
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t.start();
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}
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}
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// wait for mapping phase to be over:
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for(Thread t : mapCluster) {
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try {
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t.join();
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} catch(InterruptedException e) {
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throw new RuntimeException(e);
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}
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}
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long mapTotalTime = System.currentTimeMillis() - mapStartTime;
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// GROUP:
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long groupStartTime = System.currentTimeMillis();
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Map<String, List<String>> groupedItems = new HashMap<String, List<String>>();
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Iterator<MappedItem> mappedIter = mappedItems.iterator();
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while(mappedIter.hasNext()) {
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MappedItem item = mappedIter.next();
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String word = item.getWord();
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String file = item.getFile();
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List<String> list = groupedItems.get(word);
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if (list == null) {
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list = new ArrayList<String>();
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groupedItems.put(word, list);
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}
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list.add(file);
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}
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long groupTotalTime = System.currentTimeMillis() - groupStartTime;
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// REDUCE:
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long reduceStartTime = System.currentTimeMillis();
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final ReduceCallback<String, String, Integer> reduceCallback = new ReduceCallback<String, String, Integer>() {
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@Override
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public synchronized void reduceDone(String k, Map<String, Integer> v) {
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output.put(k, v);
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}
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};
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List<Thread> reduceCluster = new ArrayList<Thread>(groupedItems.size());
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// Replace this constant if you want to try different values for performance tests
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final int WORDS_PER_REDUCE_THREAD = 500; // Between 100 and 1000
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List<Map<String, List<String>>> reduceChunks = new ArrayList<>();
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Map<String, List<String>> currentChunk = new HashMap<>();
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int count = 0;
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// Build chunks of words (100-1000 per thread)
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for (Map.Entry<String, List<String>> entry : groupedItems.entrySet()) {
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currentChunk.put(entry.getKey(), entry.getValue());
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count++;
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if (count >= WORDS_PER_REDUCE_THREAD) {
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reduceChunks.add(currentChunk);
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currentChunk = new HashMap<>();
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count = 0;
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}
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}
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if (!currentChunk.isEmpty()) {
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reduceChunks.add(currentChunk);
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}
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for (final Map<String, List<String>> chunk : reduceChunks) {
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Thread t = new Thread(new Runnable() {
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@Override
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public void run() {
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for (Map.Entry<String, List<String>> entry : chunk.entrySet()) {
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reduce(entry.getKey(), entry.getValue(), reduceCallback);
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}
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}
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});
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reduceCluster.add(t);
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t.start();
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}
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// wait for reducing phase to be over:
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for(Thread t : reduceCluster) {
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try {
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t.join();
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} catch(InterruptedException e) {
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throw new RuntimeException(e);
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}
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}
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long endTime = System.currentTimeMillis();
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long reduceTotalTime = endTime - startTime;
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long totalTime = endTime - startTime;
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System.out.println("Distributed MapReduce Results:");
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System.out.println("\tMap Time: " + mapTotalTime);
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System.out.println("\tGroup Time: " + groupTotalTime);
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System.out.println("\tReduce Time: " + reduceTotalTime);
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System.out.println("\tTotal Time: " + totalTime + "\n");
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}
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}
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public static void map(String file, List<String> lines, MapCallback<String, MappedItem> callback) {
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List<MappedItem> results = new ArrayList<MappedItem>();
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for (String line : lines) {
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String[] words = line.trim().split("\s+");
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for(String word: words) {
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word = word.replaceAll("[^a-zA-Z]", "").toLowerCase();
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if (!word.isEmpty()) {
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results.add(new MappedItem(word, file));
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}
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}
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}
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callback.mapDone(file, results);
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}
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public static void map(String file, String contents, List<MappedItem> mappedItems) {
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String[] words = contents.trim().split("\s+");
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for(String word: words) {
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word = word.replaceAll("[^a-zA-Z]", "").toLowerCase();
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if (!word.isEmpty()) {
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mappedItems.add(new MappedItem(word, file));
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}
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}
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}
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public static void reduce(String word, List<String> list, Map<String, Map<String, Integer>> output) {
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Map<String, Integer> reducedList = new HashMap<String, Integer>();
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for(String file: list) {
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Integer occurrences = reducedList.get(file);
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if (occurrences == null) {
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reducedList.put(file, 1);
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} else {
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reducedList.put(file, occurrences.intValue() + 1);
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}
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}
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output.put(word, reducedList);
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}
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public static void reduce(String word, List<String> list, ReduceCallback<String, String, Integer> callback) {
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Map<String, Integer> reducedList = new HashMap<String, Integer>();
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for(String file: list) {
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Integer occurrences = reducedList.get(file);
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if (occurrences == null) {
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reducedList.put(file, 1);
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} else {
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reducedList.put(file, occurrences.intValue() + 1);
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}
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}
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callback.reduceDone(word, reducedList);
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}
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public static interface MapCallback<E, V> {
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public void mapDone(E key, List<V> values);
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}
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public static interface ReduceCallback<E, K, V> {
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public void reduceDone(E e, Map<K,V> results);
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}
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private static class MappedItem {
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private final String word;
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private final String file;
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public MappedItem(String word, String file) {
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this.word = word;
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this.file = file;
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}
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public String getWord() {
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return word;
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}
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public String getFile() {
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return file;
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}
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@Override
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public String toString() {
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return "[\"" + word + "\",\"" + file + "\"]";
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}
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}
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private static String readFile(String pathname) throws IOException {
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File file = new File(pathname);
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StringBuilder fileContents = new StringBuilder((int) file.length());
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Scanner scanner = new Scanner(new BufferedReader(new FileReader(file)));
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String lineSeparator = System.getProperty("line.separator");
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try {
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if (scanner.hasNextLine()) {
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fileContents.append(scanner.nextLine());
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}
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while (scanner.hasNextLine()) {
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fileContents.append(lineSeparator + scanner.nextLine());
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}
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return fileContents.toString();
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} finally {
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scanner.close();
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}
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}
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private static List<String> splitLongLine(String line) {
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List<String> result = new ArrayList<>();
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while (line.length() > 80) {
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int splitAt = line.lastIndexOf(' ', 80);
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if (splitAt <= 0) splitAt = 80;
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result.add(line.substring(0, splitAt));
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line = line.substring(splitAt).trim();
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}
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if (!line.isEmpty()) result.add(line);
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return result;
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}
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}
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