Example: update wordcount example

Added a QFileDialog to let the user select a path. Before, the path
was statically assigned with "../../" , which is not optimal.
I also modified the findFiles function to check for text files in
general and not only *.cpp and *.h files. Lastly the result of the
word counting is now displayed on the console, as I think this is an
informative output from this example.

Task-number: QTBUG-111165
Change-Id: Ie27c6acb4f79a78e3bef141edb92de08901fde71
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
(cherry picked from commit d795dfaee7093a30b278e6e8b9dea30c2e7a2106)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

doc/global/manifest-meta.qdocconf

@@ -253,7 +253,7 @@ manifestmeta.thumbnail.names    =      "QtCore/Contiguous Cache Example" \
                                        "QtCore/Semaphores Example" \
                                        "QtCore/Wait Conditions Example" \
                                        "QtConcurrent/Map Example" \
-                                       "QtConcurrent/QtConcurrent Word Count Example" \
+                                       "QtConcurrent/Word Count" \
                                        "QtConcurrent/Run Function Example" \
                                        "QtGui/Raster Window Example" \
                                        "QtNetwork/Network Download*" \

examples/qtconcurrent/wordcount/doc/src/qtconcurrent-wordcount.qdoc

@@ -1,15 +1,44 @@
-// Copyright (C) 2016 The Qt Company Ltd.
+// Copyright (C) 2023 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
 
 /*!
     \example wordcount
-    \title QtConcurrent Word Count Example
+    \meta tags {threads, console}
-    \brief Demonstrates how to use the map-reduce algorithm.
+    \title Word Count
     \ingroup qtconcurrentexamples
+    \brief Demonstrates how to use the map-reduce algorithm.
 
-    The QtConcurrent Word Count example demonstrates the use of the map-reduce
+    The Qt Concurrent \e {Word Count} example demonstrates the use of the
-    algorithm when applied to the problem of counting words in a collection
+    map-reduce algorithm when applied to the problem of counting words in a
-    of files.
+    collection of files.
 
-    This is a command-line application.
+    First, the Application starts a QFileDialog to select a starting
+    path, and then prints the output to the console.
+
+    \include examples-run.qdocinc
+
+    \section1 Comparing the operations
+
+    Compare a single-threaded, sequential approach to counting the words in
+    the text files to a multithreaded approach with mappedReduced():
+
+    \dots
+    \snippet wordcount/main.cpp 1
+    \dots
+    \snippet wordcount/main.cpp 2
+    \dots
+
+    The first argument to the \l {QtConcurrent::}{mappedReduced} function is the
+    container to operate on. The second argument is the mapping function
+    \c {countWords()}. It is called in parallel by multiple threads. The
+    third argument is the reducing function \c {reduce()}. It is called
+    once for each result returned by the mapping function, and generates the
+    final computation result.
+
+    The function returns a QFuture object of type \c WordCount. Call the
+    \l {QFuture::}{result} function immediately on this QFuture to block further
+    execution until the result becomes available.
+
+    \note The mapping function must be thread-safe since it is called from
+    multiple threads.
 */

examples/qtconcurrent/wordcount/main.cpp

@@ -1,43 +1,18 @@
-// Copyright (C) 2016 The Qt Company Ltd.
+// Copyright (C) 2023 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
-#include <QList>
+#include <QtWidgets/qfiledialog.h>
-#include <QMap>
+#include <QtWidgets/qapplication.h>
-#include <QTextStream>
+#include <QtCore/qmimedatabase.h>
-#include <QString>
+#include <QtCore/qelapsedtimer.h>
-#include <QStringList>
+#include <QtConcurrent/qtconcurrentmap.h>
-#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;
 
-/*
+void printHighestResult(const WordCount &, qsizetype);
-    Single threaded word counter function.
+QStringList findFiles(const QString &);
-*/
+
+// Single threaded word counter function.
 WordCount singleThreadedWordCount(const QStringList &files)
 {
     WordCount wordCount;
@@ -46,7 +21,7 @@ WordCount singleThreadedWordCount(const QStringList &files)
         f.open(QIODevice::ReadOnly);
         QTextStream textStream(&f);
         while (!textStream.atEnd()) {
-            const auto words =  textStream.readLine().split(' ');
+            const auto words =  textStream.readLine().split(' ', Qt::SkipEmptyParts);
             for (const QString &word : words)
                 wordCount[word] += 1;
         }
@@ -54,7 +29,6 @@ WordCount singleThreadedWordCount(const QStringList &files)
     return wordCount;
 }
 
-
 // countWords counts the words in a single file. This function is
 // called in parallel by several threads and must be thread
 // safe.
@@ -66,7 +40,7 @@ WordCount countWords(const QString &file)
     WordCount wordCount;
 
     while (!textStream.atEnd()) {
-        const auto words =  textStream.readLine().split(' ');
+        const auto words =  textStream.readLine().split(' ', Qt::SkipEmptyParts);
         for (const QString &word : words)
             wordCount[word] += 1;
     }
@@ -86,33 +60,93 @@ void reduce(WordCount &result, const WordCount &w)
 int main(int argc, char** argv)
 {
     QApplication app(argc, argv);
-    qDebug() << "finding files...";
+    app.setOrganizationName("QtProject");
-    QStringList files = findFiles("../../", QStringList() << "*.cpp" << "*.h");
+    app.setApplicationName(QCoreApplication::translate("main", "Word Count"));
-    qDebug() << files.count() << "files";
 
-    qDebug() << "warmup";
+    QFileDialog fileDialog;
-    {
+    fileDialog.setOption(QFileDialog::ReadOnly);
-        WordCount total = singleThreadedWordCount(files);
+    // Grab the directory path from the dialog
-    }
+    auto dirPath = QFileDialog::getExistingDirectory(nullptr,
+                                QCoreApplication::translate("main","Select a Folder"),
+                                QDir::currentPath());
 
-    qDebug() << "warmup done";
+    QStringList files = findFiles(dirPath);
+    qDebug() << QCoreApplication::translate("main", "Indexing %1 files in %2")
+        .arg(files.size()).arg(dirPath);
 
-    int singleThreadTime = 0;
+    // Start the single threaded operation
+    qint64 singleThreadTime;
     {
         QElapsedTimer timer;
         timer.start();
+    //! [1]
         WordCount total = singleThreadedWordCount(files);
+    //! [1]
         singleThreadTime = timer.elapsed();
-        qDebug() << "single thread" << singleThreadTime;
+        qDebug() << QCoreApplication::translate("main", "Single threaded scanning took %1 ms")
+            .arg(singleThreadTime);
     }
-
+    // Start the multithreaded mappedReduced operation.
-    int mapReduceTime = 0;
+    qint64 mapReduceTime;
     {
         QElapsedTimer timer;
         timer.start();
-        WordCount total = mappedReduced(files, countWords, reduce).result();
+    //! [2]
+        WordCount total = QtConcurrent::mappedReduced(files, countWords, reduce).result();
+    //! [2]
         mapReduceTime = timer.elapsed();
-        qDebug() << "MapReduce" << mapReduceTime;
+        qDebug() << QCoreApplication::translate("main", "MapReduce scanning took %1 ms")
+            .arg(mapReduceTime);
+        qDebug() << QCoreApplication::translate("main", "MapReduce speedup: %1")
+            .arg(((double)singleThreadTime - (double)mapReduceTime) / (double)mapReduceTime + 1);
+        printHighestResult(total, 10);
     }
-    qDebug() << "MapReduce speedup x" << ((double)singleThreadTime - (double)mapReduceTime) / (double)mapReduceTime + 1;
+}
+
+// Utility function that recursively searches for text files.
+QStringList findFiles(const QString &startDir)
+{
+    QStringList names;
+    QDir dir(startDir);
+    static const QMimeDatabase db;
+
+    const auto files = dir.entryList(QDir::Files);
+    for (const QString &file : files) {
+        const auto path = startDir + QDir::separator() + file;
+        const QMimeType mime = db.mimeTypeForFile(QFileInfo(path));
+        const auto mimeTypesForFile = mime.parentMimeTypes();
+
+        for (const auto &i : mimeTypesForFile) {
+            if (i.contains("text", Qt::CaseInsensitive)
+                || mime.comment().contains("text", Qt::CaseInsensitive)) {
+                names += startDir + QDir::separator() + file;
+            }
+        }
+    }
+
+    const auto subdirs =  dir.entryList(QDir::AllDirs | QDir::NoDotAndDotDot);
+    for (const QString &subdir : subdirs) {
+        if (names.length() >= 20000) {
+            qDebug() << QCoreApplication::translate("main", "Too many files! Aborting ...");
+            exit(-1);
+        }
+        names += findFiles(startDir + QDir::separator() + subdir);
+    }
+    return names;
+}
+
+// Utility function that prints the results of the map in decreasing order based on the value.
+void printHighestResult(const WordCount &countedWords, qsizetype nResults)
+{
+    using pair = QPair<QString, int>;
+    QList<pair> vec;
+
+    std::copy(countedWords.keyValueBegin(), countedWords.keyValueEnd(),
+              std::back_inserter<QList<pair>>(vec));
+    std::sort(vec.begin(), vec.end(),
+              [](const pair &l, const pair &r) { return l.second > r.second; });
+
+    qDebug() << QCoreApplication::translate("main", "Most occurring words are:");
+    for (qsizetype i = 0; i < qMin(vec.size(), nResults); ++i)
+        qDebug() << vec[i].first << " : " << vec[i].second;
 }