Initial import from the monolithic Qt.

This is the beginning of revision history for this module. If you
want to look at revision history older than this, please refer to the
Qt Git wiki for how to use Git history grafting. At the time of
writing, this wiki is located here:

http://qt.gitorious.org/qt/pages/GitIntroductionWithQt

If you have already performed the grafting and you don't see any
history beyond this commit, try running "git log" with the "--follow"
argument.

Branched from the monolithic repo, Qt master branch, at commit
896db169ea224deb96c59ce8af800d019de63f12

1 files changed, 255 insertions, 0 deletions

diff --git a/src/corelib/concurrent/qtconcurrentreducekernel.h b/src/corelib/concurrent/qtconcurrentreducekernel.h
new file mode 100644
index 0000000000..d8651ab4cc
--- /dev/null
+++ b/src/corelib/concurrent/qtconcurrentreducekernel.h
@@ -0,0 +1,255 @@
+/****************************************************************************
+**
+** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights.  These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QTCONCURRENT_REDUCEKERNEL_H
+#define QTCONCURRENT_REDUCEKERNEL_H
+
+#include <QtCore/qglobal.h>
+
+#ifndef QT_NO_CONCURRENT
+
+#include <QtCore/qatomic.h>
+#include <QtCore/qlist.h>
+#include <QtCore/qmap.h>
+#include <QtCore/qmutex.h>
+#include <QtCore/qthread.h>
+#include <QtCore/qthreadpool.h>
+#include <QtCore/qvector.h>
+
+QT_BEGIN_HEADER
+QT_BEGIN_NAMESPACE
+
+QT_MODULE(Core)
+
+namespace QtConcurrent {
+
+#ifndef qdoc
+
+/*
+    The ReduceQueueStartLimit and ReduceQueueThrottleLimit constants
+    limit the reduce queue size for MapReduce. When the number of
+    reduce blocks in the queue exceeds ReduceQueueStartLimit,
+    MapReduce won't start any new threads, and when it exceeds
+    ReduceQueueThrottleLimit running threads will be stopped.
+*/
+enum {
+    ReduceQueueStartLimit = 20,
+    ReduceQueueThrottleLimit = 30
+};
+
+// IntermediateResults holds a block of intermediate results from a
+// map or filter functor. The begin/end offsets indicates the origin
+// and range of the block.
+template <typename T>
+class IntermediateResults
+{
+public:
+    int begin, end;
+    QVector<T> vector;
+};
+
+#endif // qdoc
+
+enum ReduceOption {
+    UnorderedReduce = 0x1,
+    OrderedReduce = 0x2,
+    SequentialReduce = 0x4
+    // ParallelReduce = 0x8
+};
+Q_DECLARE_FLAGS(ReduceOptions, ReduceOption)
+Q_DECLARE_OPERATORS_FOR_FLAGS(ReduceOptions)
+
+#ifndef qdoc
+
+// supports both ordered and out-of-order reduction
+template <typename ReduceFunctor, typename ReduceResultType, typename T>
+class ReduceKernel
+{
+    typedef QMap<int, IntermediateResults<T> > ResultsMap;
+
+    const ReduceOptions reduceOptions;
+
+    QMutex mutex;
+    int progress, resultsMapSize, threadCount;
+    ResultsMap resultsMap;
+
+    bool canReduce(int begin) const
+    {
+        return (((reduceOptions & UnorderedReduce)
+                 && progress == 0)
+                || ((reduceOptions & OrderedReduce)
+                    && progress == begin));
+    }
+
+    void reduceResult(ReduceFunctor &reduce,
+                      ReduceResultType &r,
+                      const IntermediateResults<T> &result)
+    {
+        for (int i = 0; i < result.vector.size(); ++i) {
+            reduce(r, result.vector.at(i));
+        }
+    }
+
+    void reduceResults(ReduceFunctor &reduce,
+                       ReduceResultType &r,
+                       ResultsMap &map)
+    {
+        typename ResultsMap::iterator it = map.begin();
+        while (it != map.end()) {
+            reduceResult(reduce, r, it.value());
+            ++it;
+        }
+    }
+
+public:
+    ReduceKernel(ReduceOptions _reduceOptions)
+        : reduceOptions(_reduceOptions), progress(0), resultsMapSize(0), 
+          threadCount(QThreadPool::globalInstance()->maxThreadCount())
+    { }
+
+    void runReduce(ReduceFunctor &reduce,
+                   ReduceResultType &r,
+                   const IntermediateResults<T> &result)
+    {
+        QMutexLocker locker(&mutex);
+        if (!canReduce(result.begin)) {
+            ++resultsMapSize;
+            resultsMap.insert(result.begin, result);
+            return;
+        }
+
+        if (reduceOptions & UnorderedReduce) {
+            // UnorderedReduce
+            progress = -1;
+
+            // reduce this result
+            locker.unlock();
+            reduceResult(reduce, r, result);
+            locker.relock();
+
+            // reduce all stored results as well
+            while (!resultsMap.isEmpty()) {
+                ResultsMap resultsMapCopy = resultsMap;
+                resultsMap.clear();
+
+                locker.unlock();
+                reduceResults(reduce, r, resultsMapCopy);
+                locker.relock();
+
+                resultsMapSize -= resultsMapCopy.size();
+            }
+
+            progress = 0;
+        } else {
+            // reduce this result
+            locker.unlock();
+            reduceResult(reduce, r, result);
+            locker.relock();
+
+            // OrderedReduce
+            progress += result.end - result.begin;
+
+            // reduce as many other results as possible
+            typename ResultsMap::iterator it = resultsMap.begin();
+            while (it != resultsMap.end()) {
+                if (it.value().begin != progress)
+                    break;
+
+                locker.unlock();
+                reduceResult(reduce, r, it.value());
+                locker.relock();
+
+                --resultsMapSize;
+                progress += it.value().end - it.value().begin;
+                it = resultsMap.erase(it);
+            }
+        }
+    }
+
+    // final reduction
+    void finish(ReduceFunctor &reduce, ReduceResultType &r)
+    {
+        reduceResults(reduce, r, resultsMap);
+    }
+
+    inline bool shouldThrottle()
+    {
+        return (resultsMapSize > (ReduceQueueThrottleLimit * threadCount));
+    }
+
+    inline bool shouldStartThread()
+    {
+        return (resultsMapSize <= (ReduceQueueStartLimit * threadCount));
+    }
+};
+
+template <typename Sequence, typename Base, typename Functor1, typename Functor2>
+struct SequenceHolder2 : public Base
+{
+    SequenceHolder2(const Sequence &_sequence,
+                    Functor1 functor1,
+                    Functor2 functor2,
+                    ReduceOptions reduceOptions)
+        : Base(_sequence.begin(), _sequence.end(), functor1, functor2, reduceOptions),
+          sequence(_sequence)
+    { }
+
+    Sequence sequence;
+
+    void finish()
+    {
+        Base::finish();
+        // Clear the sequence to make sure all temporaries are destroyed
+        // before finished is signaled.
+        sequence = Sequence();
+    }
+};
+
+#endif //qdoc
+
+} // namespace QtConcurrent
+
+QT_END_NAMESPACE
+QT_END_HEADER
+
+#endif // QT_NO_CONCURRENT
+
+#endif