main.cpp Example File
wordcount/main.cpp
#include <QList>
#include <QMap>
#include <QTextStream>
#include <QString>
#include <QStringList>
#include <QDir>
#include <QTime>
#include <QApplication>
#include <QDebug>
#include <qtconcurrentmap.h>
using namespace QtConcurrent;
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;
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;
}
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;
}
void reduce(WordCount &result, const WordCount &w)
{
QMapIterator<QString, int> i(w);
while (i.hasNext()) {
i.next();
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;
{
QTime time;
time.start();
WordCount total = singleThreadedWordCount(files);
singleThreadTime = time.elapsed();
qDebug() << "single thread" << singleThreadTime;
}
int mapReduceTime = 0;
{
QTime time;
time.start();
WordCount total = mappedReduced(files, countWords, reduce);
mapReduceTime = time.elapsed();
qDebug() << "MapReduce" << mapReduceTime;
}
qDebug() << "MapReduce speedup x" << ((double)singleThreadTime - (double)mapReduceTime) / (double)mapReduceTime + 1;
}