From 429218eaf22c1bde24ba6875895c33facfa6ae12 Mon Sep 17 00:00:00 2001
From: Emmanuel Pescosta <emmanuelpescosta099@gmail.com>
Date: Sun, 28 Oct 2012 17:58:06 +0100
Subject: [PATCH] Implemented multithreading in KFileItemModelSortAlgorithm.
 Use as many threads as possible. Thanks to Frank Reininghaus for all his
 suggestions.

REVIEW: 107025
---
 .../private/kfileitemmodelsortalgorithm.cpp   | 33 +++++++++++++++++++
 .../private/kfileitemmodelsortalgorithm.h     |  9 +++++
 2 files changed, 42 insertions(+)

diff --git a/dolphin/src/kitemviews/private/kfileitemmodelsortalgorithm.cpp b/dolphin/src/kitemviews/private/kfileitemmodelsortalgorithm.cpp
index e0aac13de3..63eaea5578 100644
--- a/dolphin/src/kitemviews/private/kfileitemmodelsortalgorithm.cpp
+++ b/dolphin/src/kitemviews/private/kfileitemmodelsortalgorithm.cpp
@@ -19,9 +19,20 @@
 
 #include "kfileitemmodelsortalgorithm.h"
 
+#include <QThread>
+#include <QtCore>
+
 void KFileItemModelSortAlgorithm::sort(KFileItemModel* model,
                                        QList<KFileItemModel::ItemData*>::iterator begin,
                                        QList<KFileItemModel::ItemData*>::iterator end)
+{
+    static const int numberOfThreads = QThread::idealThreadCount();
+    parallelSort(model, begin, end, numberOfThreads);
+}
+
+void KFileItemModelSortAlgorithm::sequentialSort(KFileItemModel* model,
+                                                 QList< KFileItemModel::ItemData* >::iterator begin,
+                                                 QList< KFileItemModel::ItemData* >::iterator end)
 {
     // The implementation is based on qStableSortHelper() from qalgorithms.h
     // Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
@@ -37,6 +48,28 @@ void KFileItemModelSortAlgorithm::sort(KFileItemModel* model,
     merge(model, begin, middle, end);
 }
 
+void KFileItemModelSortAlgorithm::parallelSort(KFileItemModel* model,
+                                               QList< KFileItemModel::ItemData* >::iterator begin,
+                                               QList< KFileItemModel::ItemData* >::iterator end,
+                                               const int numberOfThreads)
+{
+    const int span = end - begin;
+
+    if (numberOfThreads > 1 && span > 100) {
+        const int newNumberOfThreads = numberOfThreads / 2;
+        const QList<KFileItemModel::ItemData*>::iterator middle = begin + span / 2;
+
+        QFuture<void> future = QtConcurrent::run(parallelSort, model, begin, middle, newNumberOfThreads);
+        parallelSort(model, middle, end, newNumberOfThreads);
+
+        future.waitForFinished();
+
+        merge(model, begin, middle, end);
+    } else {
+        sequentialSort(model, begin, end);
+    }
+}
+
 void KFileItemModelSortAlgorithm::merge(KFileItemModel* model,
                                         QList<KFileItemModel::ItemData*>::iterator begin,
                                         QList<KFileItemModel::ItemData*>::iterator pivot,
diff --git a/dolphin/src/kitemviews/private/kfileitemmodelsortalgorithm.h b/dolphin/src/kitemviews/private/kfileitemmodelsortalgorithm.h
index 3a596dff56..07e5d4a814 100644
--- a/dolphin/src/kitemviews/private/kfileitemmodelsortalgorithm.h
+++ b/dolphin/src/kitemviews/private/kfileitemmodelsortalgorithm.h
@@ -44,6 +44,15 @@ public:
                      QList<KFileItemModel::ItemData*>::iterator end);
 
 private:
+    static void sequentialSort(KFileItemModel* model,
+                               QList<KFileItemModel::ItemData*>::iterator begin,
+                               QList<KFileItemModel::ItemData*>::iterator end);
+
+    static void parallelSort(KFileItemModel* model,
+                             QList<KFileItemModel::ItemData*>::iterator begin,
+                             QList<KFileItemModel::ItemData*>::iterator end,
+                             const int numberOfThreads);
+
     static void merge(KFileItemModel* model,
                       QList<KFileItemModel::ItemData*>::iterator begin,
                       QList<KFileItemModel::ItemData*>::iterator pivot,