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# qtconcurrentmapkernel.h

Go to the documentation of this file.

    00001 /****************************************************************************
    00002 **
    00003 ** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
    00004 ** All rights reserved.
    00005 ** Contact: Nokia Corporation (qt-info@nokia.com)
    00006 **
    00007 ** This file is part of the QtCore module of the Qt Toolkit.
    00008 **
    00009 ** $QT_BEGIN_LICENSE:LGPL$
    00010 ** Commercial Usage
    00011 ** Licensees holding valid Qt Commercial licenses may use this file in
    00012 ** accordance with the Qt Commercial License Agreement provided with the
    00013 ** Software or, alternatively, in accordance with the terms contained in
    00014 ** a written agreement between you and Nokia.
    00015 **
    00016 ** GNU Lesser General Public License Usage
    00017 ** Alternatively, this file may be used under the terms of the GNU Lesser
    00018 ** General Public License version 2.1 as published by the Free Software
    00019 ** Foundation and appearing in the file LICENSE.LGPL included in the
    00020 ** packaging of this file.  Please review the following information to
    00021 ** ensure the GNU Lesser General Public License version 2.1 requirements
    00022 ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
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    00024 ** In addition, as a special exception, Nokia gives you certain additional
    00025 ** rights.  These rights are described in the Nokia Qt LGPL Exception
    00026 ** version 1.1, included in the file LGPL_EXCEPTION.txt in this module.
    00027 **
    00028 ** GNU General Public License Usage
    00029 ** Alternatively, this file may be used under the terms of the GNU
    00030 ** General Public License version 3.0 as published by the Free Software
    00031 ** Foundation and appearing in the file LICENSE.GPL included in the
    00032 ** packaging of this file.  Please review the following information to
    00033 ** ensure the GNU General Public License version 3.0 requirements will be
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    00035 **
    00036 ** If you have questions regarding the use of this file, please contact
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    00038 ** $QT_END_LICENSE$
    00039 **
    00040 ****************************************************************************/
    00041
    00042 #ifndef QTCONCURRENT_MAPKERNEL_H
    00043 #define QTCONCURRENT_MAPKERNEL_H
    00044
    00045 #include <QtCore/qglobal.h>
    00046
    00047 #ifndef QT_NO_CONCURRENT
    00048
    00049 #include <QtCore/qtconcurrentiteratekernel.h>
    00050 #include <QtCore/qtconcurrentreducekernel.h>
    00051
    00052 QT_BEGIN_HEADER
    00053 QT_BEGIN_NAMESPACE
    00054
    00055 QT_MODULE(Core)
    00056
    00057 #ifndef qdoc
    00058 namespace QtConcurrent {
    00059
    00060 // map kernel, works with both parallel-for and parallel-while
    00061 template <typename Iterator, typename MapFunctor>
    00062 class MapKernel : public IterateKernel<Iterator, void>
    00063 {
    00064     MapFunctor map;
    00065 public:
    00066     typedef void ReturnType;
    00067     MapKernel(Iterator begin, Iterator end, MapFunctor _map)
    00068         : IterateKernel<Iterator, void>(begin, end), map(_map)
    00069     { }
    00070
    00071     bool runIteration(Iterator it, int, void *)
    00072     {
    00073         map(*it);
    00074         return false;
    00075     }
    00076
    00077     bool runIterations(Iterator sequenceBeginIterator, int beginIndex, int endIndex, void *)
    00078     {
    00079         Iterator it = sequenceBeginIterator;
    00080         advance(it, beginIndex);
    00081         for (int i = beginIndex; i < endIndex; ++i) {
    00082             runIteration(it, i, 0);
    00083             advance(it, 1);
    00084         }
    00085
    00086         return false;
    00087     }
    00088 };
    00089
    00090 template <typename ReducedResultType,
    00091           typename Iterator,
    00092           typename MapFunctor,
    00093           typename ReduceFunctor,
    00094           typename Reducer = ReduceKernel<ReduceFunctor,
    00095                                           ReducedResultType,
    00096                                           typename MapFunctor::result_type> >
    00097 class MappedReducedKernel : public IterateKernel<Iterator, ReducedResultType>
    00098 {
    00099     ReducedResultType reducedResult;
    00100     MapFunctor map;
    00101     ReduceFunctor reduce;
    00102     Reducer reducer;
    00103 public:
    00104     typedef ReducedResultType ReturnType;
    00105     MappedReducedKernel(Iterator begin, Iterator end, MapFunctor _map, ReduceFunctor _reduce, ReduceOptions reduceOptions)
    00106         : IterateKernel<Iterator, ReducedResultType>(begin, end), reducedResult(), map(_map), reduce(_reduce), reducer(reduceOptions)
    00107     { }
    00108
    00109     MappedReducedKernel(ReducedResultType initialValue,
    00110                      MapFunctor _map,
    00111                      ReduceFunctor _reduce)
    00112         : reducedResult(initialValue), map(_map), reduce(_reduce)
    00113     { }
    00114
    00115     bool runIteration(Iterator it, int index, ReducedResultType *)
    00116     {
    00117         IntermediateResults<typename MapFunctor::result_type> results;
    00118         results.begin = index;
    00119         results.end = index + 1;
    00120
    00121         results.vector.append(map(*it));
    00122         reducer.runReduce(reduce, reducedResult, results);
    00123         return false;
    00124     }
    00125
    00126     bool runIterations(Iterator sequenceBeginIterator, int begin, int end, ReducedResultType *)
    00127     {
    00128         IntermediateResults<typename MapFunctor::result_type> results;
    00129         results.begin = begin;
    00130         results.end = end;
    00131         results.vector.reserve(end - begin);
    00132
    00133         Iterator it = sequenceBeginIterator;
    00134         advance(it, begin);
    00135         for (int i = begin; i < end; ++i) {
    00136             results.vector.append(map(*(it)));
    00137             advance(it, 1);
    00138         }
    00139
    00140         reducer.runReduce(reduce, reducedResult, results);
    00141         return false;
    00142     }
    00143
    00144     void finish()
    00145     {
    00146         reducer.finish(reduce, reducedResult);
    00147     }
    00148
    00149     bool shouldThrottleThread()
    00150     {
    00151         return IterateKernel<Iterator, ReducedResultType>::shouldThrottleThread() || reducer.shouldThrottle();
    00152     }
    00153
    00154     bool shouldStartThread()
    00155     {
    00156         return IterateKernel<Iterator, ReducedResultType>::shouldStartThread() && reducer.shouldStartThread();
    00157     }
    00158
    00159     typedef ReducedResultType ResultType;
    00160     ReducedResultType *result()
    00161     {
    00162         return &reducedResult;
    00163     }
    00164 };
    00165
    00166 template <typename Iterator, typename MapFunctor>
    00167 class MappedEachKernel : public IterateKernel<Iterator, typename MapFunctor::result_type>
    00168 {
    00169     MapFunctor map;
    00170     typedef typename MapFunctor::result_type T;
    00171 public:
    00172     typedef T ReturnType;
    00173     typedef T ResultType;
    00174
    00175     MappedEachKernel(Iterator begin, Iterator end, MapFunctor _map)
    00176         : IterateKernel<Iterator, T>(begin, end), map(_map) { }
    00177
    00178     bool runIteration(Iterator it, int,  T *result)
    00179     {
    00180         *result = map(*it);
    00181         return true;
    00182     }
    00183
    00184     bool runIterations(Iterator sequenceBeginIterator, int begin, int end, T *results)
    00185     {
    00186
    00187         Iterator it = sequenceBeginIterator;
    00188         advance(it, begin);
    00189         for (int i = begin; i < end; ++i) {
    00190             runIteration(it, i, results + (i - begin));
    00191             advance(it, 1);
    00192         }
    00193
    00194         return true;
    00195     }
    00196 };
    00197
    00198 template <typename Iterator, typename Functor>
    00199 inline ThreadEngineStarter<void> startMap(Iterator begin, Iterator end, Functor functor)
    00200 {
    00201     return startThreadEngine(new MapKernel<Iterator, Functor>(begin, end, functor));
    00202 }
    00203
    00204 template <typename T, typename Iterator, typename Functor>
    00205 inline ThreadEngineStarter<T> startMapped(Iterator begin, Iterator end, Functor functor)
    00206 {
    00207     return startThreadEngine(new MappedEachKernel<Iterator, Functor>(begin, end, functor));
    00208 }
    00209
    00210 /*
    00211     The SequnceHolder class is used to hold a reference to the
    00212     sequence we are working on.
    00213 */
    00214 template <typename Sequence, typename Base, typename Functor>
    00215 struct SequenceHolder1 : public Base
    00216 {
    00217     SequenceHolder1(const Sequence &_sequence, Functor functor)
    00218         : Base(_sequence.begin(), _sequence.end(), functor), sequence(_sequence)
    00219     { }
    00220
    00221     Sequence sequence;
    00222
    00223     void finish()
    00224     {
    00225         Base::finish();
    00226         // Clear the sequence to make sure all temporaries are destroyed
    00227         // before finished is signaled.
    00228         sequence = Sequence();
    00229     }
    00230 };
    00231
    00232 template <typename T, typename Sequence, typename Functor>
    00233 inline ThreadEngineStarter<T> startMapped(const Sequence &sequence, Functor functor)
    00234 {
    00235     typedef SequenceHolder1<Sequence,
    00236                             MappedEachKernel<typename Sequence::const_iterator , Functor>, Functor>
    00237                             SequenceHolderType;
    00238
    00239     return startThreadEngine(new SequenceHolderType(sequence, functor));
    00240 }
    00241
    00242 template <typename IntermediateType, typename ResultType, typename Sequence, typename MapFunctor, typename ReduceFunctor>
    00243 inline ThreadEngineStarter<ResultType> startMappedReduced(const Sequence & sequence,
    00244                                                            MapFunctor mapFunctor, ReduceFunctor reduceFunctor,
    00245                                                            ReduceOptions options)
    00246 {
    00247     typedef typename Sequence::const_iterator Iterator;
    00248     typedef ReduceKernel<ReduceFunctor, ResultType, IntermediateType> Reducer;
    00249     typedef MappedReducedKernel<ResultType, Iterator, MapFunctor, ReduceFunctor, Reducer> MappedReduceType;
    00250     typedef SequenceHolder2<Sequence, MappedReduceType, MapFunctor, ReduceFunctor> SequenceHolderType;
    00251     return startThreadEngine(new SequenceHolderType(sequence, mapFunctor, reduceFunctor, options));
    00252 }
    00253
    00254 template <typename IntermediateType, typename ResultType, typename Iterator, typename MapFunctor, typename ReduceFunctor>
    00255 inline ThreadEngineStarter<ResultType> startMappedReduced(Iterator begin, Iterator end,
    00256                                                            MapFunctor mapFunctor, ReduceFunctor reduceFunctor,
    00257                                                            ReduceOptions options)
    00258 {
    00259     typedef ReduceKernel<ReduceFunctor, ResultType, IntermediateType> Reducer;
    00260     typedef MappedReducedKernel<ResultType, Iterator, MapFunctor, ReduceFunctor, Reducer> MappedReduceType;
    00261     return startThreadEngine(new MappedReduceType(begin, end, mapFunctor, reduceFunctor, options));
    00262 }
    00263
    00264 } // namespace QtConcurrent
    00265
    00266 #endif //qdoc
    00267
    00268 QT_END_NAMESPACE
    00269 QT_END_HEADER
    00270
    00271 #endif // QT_NO_CONCURRENT
    00272
    00273 #endif