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| ** This file is part of the examples of the Qt Toolkit. |
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| |
| #include <QList> |
| #include <QMap> |
| #include <QTextStream> |
| #include <QString> |
| #include <QStringList> |
| #include <QDir> |
| #include <QElapsedTimer> |
| #include <QApplication> |
| #include <QDebug> |
| |
| #include <qtconcurrentmap.h> |
| |
| using namespace QtConcurrent; |
| |
| /* |
| Utility function that recursivily searches for files. |
| */ |
| QStringList findFiles(const QString &startDir, const QStringList &filters) |
| { |
| QStringList names; |
| QDir dir(startDir); |
| |
| const auto files = dir.entryList(filters, QDir::Files); |
| for (const QString &file : files) |
| names += startDir + '/' + file; |
| |
| const auto subdirs = dir.entryList(QDir::AllDirs | QDir::NoDotAndDotDot); |
| for (const QString &subdir : subdirs) |
| names += findFiles(startDir + '/' + subdir, filters); |
| return names; |
| } |
| |
| typedef QMap<QString, int> WordCount; |
| |
| /* |
| Single threaded word counter function. |
| */ |
| WordCount singleThreadedWordCount(const QStringList &files) |
| { |
| WordCount wordCount; |
| for (const QString &file : files) { |
| QFile f(file); |
| f.open(QIODevice::ReadOnly); |
| QTextStream textStream(&f); |
| while (!textStream.atEnd()) { |
| const auto words = textStream.readLine().split(' '); |
| for (const QString &word : words) |
| wordCount[word] += 1; |
| } |
| } |
| return wordCount; |
| } |
| |
| |
| // countWords counts the words in a single file. This function is |
| // called in parallel by several threads and must be thread |
| // safe. |
| WordCount countWords(const QString &file) |
| { |
| QFile f(file); |
| f.open(QIODevice::ReadOnly); |
| QTextStream textStream(&f); |
| WordCount wordCount; |
| |
| while (!textStream.atEnd()) { |
| const auto words = textStream.readLine().split(' '); |
| for (const QString &word : words) |
| wordCount[word] += 1; |
| } |
| |
| return wordCount; |
| } |
| |
| // reduce adds the results from map to the final |
| // result. This functor will only be called by one thread |
| // at a time. |
| void reduce(WordCount &result, const WordCount &w) |
| { |
| for (auto i = w.begin(), end = w.end(); i != end; ++i) |
| result[i.key()] += i.value(); |
| } |
| |
| int main(int argc, char** argv) |
| { |
| QApplication app(argc, argv); |
| qDebug() << "finding files..."; |
| QStringList files = findFiles("../../", QStringList() << "*.cpp" << "*.h"); |
| qDebug() << files.count() << "files"; |
| |
| qDebug() << "warmup"; |
| { |
| WordCount total = singleThreadedWordCount(files); |
| } |
| |
| qDebug() << "warmup done"; |
| |
| int singleThreadTime = 0; |
| { |
| QElapsedTimer timer; |
| timer.start(); |
| WordCount total = singleThreadedWordCount(files); |
| singleThreadTime = timer.elapsed(); |
| qDebug() << "single thread" << singleThreadTime; |
| } |
| |
| int mapReduceTime = 0; |
| { |
| QElapsedTimer timer; |
| timer.start(); |
| WordCount total = mappedReduced(files, countWords, reduce); |
| mapReduceTime = timer.elapsed(); |
| qDebug() << "MapReduce" << mapReduceTime; |
| } |
| qDebug() << "MapReduce speedup x" << ((double)singleThreadTime - (double)mapReduceTime) / (double)mapReduceTime + 1; |
| } |