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     2 **

     3 ** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).

     4 ** All rights reserved.

     5 ** Contact: Nokia Corporation (qt-info@nokia.com)

     6 **

     7 ** This file is part of the examples of the Qt Toolkit.

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     9 ** $QT_BEGIN_LICENSE:LGPL$

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    13 ** contained in the Technology Preview License Agreement accompanying

    14 ** this package.

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    16 ** GNU Lesser General Public License Usage

    17 ** Alternatively, this file may be used under the terms of the GNU Lesser

    18 ** General Public License version 2.1 as published by the Free Software

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    38 ** $QT_END_LICENSE$

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    40 ****************************************************************************/

    41 

    42 #include <QList>

    43 #include <QMap>

    44 #include <QTextStream>

    45 #include <QString>

    46 #include <QStringList>

    47 #include <QDir>

    48 #include <QTime>

    49 #include <QApplication>

    50 #include <QDebug>

    51 

    52 #include <qtconcurrentmap.h>

    53 

    54 #ifndef QT_NO_CONCURRENT

    55 

    56 using namespace QtConcurrent;

    57 

    58 /*

    59     Utility function that recursivily searches for files.

    60 */

    61 QStringList findFiles(const QString &startDir, QStringList filters)

    62 {

    63     QStringList names;

    64     QDir dir(startDir);

    65 

    66     foreach (QString file, dir.entryList(filters, QDir::Files))

    67         names += startDir + "/" + file;

    68 

    69     foreach (QString subdir, dir.entryList(QDir::AllDirs | QDir::NoDotAndDotDot))

    70         names += findFiles(startDir + "/" + subdir, filters);

    71     return names;

    72 }

    73 

    74 typedef QMap<QString, int> WordCount;

    75 

    76 /*

    77     Single threaded word counter function.

    78 */

    79 WordCount singleThreadedWordCount(QStringList files)

    80 {

    81     WordCount wordCount;

    82     foreach (QString file, files) {

    83         QFile f(file);

    84         f.open(QIODevice::ReadOnly);

    85         QTextStream textStream(&f);

    86         while (textStream.atEnd() == false)

    87             foreach(QString word, textStream.readLine().split(" "))

    88                 wordCount[word] += 1;

    89 

    90     }

    91     return wordCount;

    92 }

    93 

    94 

    95 // countWords counts the words in a single file. This function is

    96 // called in parallel by several threads and must be thread

    97 // safe.

    98 WordCount countWords(const QString &file)

    99 {

   100     QFile f(file);

   101     f.open(QIODevice::ReadOnly);

   102     QTextStream textStream(&f);

   103     WordCount wordCount;

   104 

   105     while (textStream.atEnd() == false)

   106         foreach (QString word, textStream.readLine().split(" "))

   107             wordCount[word] += 1;

   108 

   109     return wordCount;

   110 }

   111 

   112 // reduce adds the results from map to the final

   113 // result. This functor will only be called by one thread

   114 // at a time.

   115 void reduce(WordCount &result, const WordCount &w)

   116 {

   117     QMapIterator<QString, int> i(w);

   118     while (i.hasNext()) {

   119         i.next();

   120         result[i.key()] += i.value();

   121     }

   122 }

   123 

   124 int main(int argc, char** argv)

   125 {

   126     QApplication app(argc, argv);

   127     qDebug() << "finding files...";

   128     QStringList files = findFiles("../../", QStringList() << "*.cpp" << "*.h");

   129     qDebug() << files.count() << "files";

   130 

   131     qDebug() << "warmup";

   132     {

   133         QTime time;

   134         time.start();

   135         WordCount total = singleThreadedWordCount(files);

   136     }

   137 

   138     qDebug() << "warmup done";

   139 

   140     int singleThreadTime = 0;

   141     {

   142         QTime time;

   143         time.start();

   144         WordCount total = singleThreadedWordCount(files);

   145         singleThreadTime = time.elapsed();

   146         qDebug() << "single thread" << singleThreadTime;

   147     }

   148 

   149     int mapReduceTime = 0;

   150     {

   151         QTime time;

   152         time.start();

   153         WordCount total = mappedReduced(files, countWords, reduce);

   154         mapReduceTime = time.elapsed();

   155         qDebug() << "MapReduce" << mapReduceTime;

   156     }

   157     qDebug() << "MapReduce speedup x" << ((double)singleThreadTime - (double)mapReduceTime) / (double)mapReduceTime + 1;

   158 }

   159 

   160 #else

   161 

   162 int main()

   163 {

   164 	qDebug() << "Qt Concurrent is not yet supported on this platform";

   165 }

   166 

   167 #endif