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| |
| #ifndef QTCONCURRENT_MEDIAN_H |
| #define QTCONCURRENT_MEDIAN_H |
| |
| #include <QtConcurrent/qtconcurrent_global.h> |
| |
| #ifndef QT_NO_CONCURRENT |
| |
| #include <QtCore/qvector.h> |
| |
| #include <algorithm> |
| |
| QT_BEGIN_NAMESPACE |
| |
| |
| #ifndef Q_QDOC |
| |
| namespace QtConcurrent { |
| |
| template <typename T> |
| class Median |
| { |
| public: |
| Median(int _bufferSize) |
| : currentMedian(), bufferSize(_bufferSize), currentIndex(0), valid(false), dirty(true) |
| { |
| values.resize(bufferSize); |
| } |
| |
| void reset() |
| { |
| values.fill(0); |
| currentIndex = 0; |
| valid = false; |
| dirty = true; |
| } |
| |
| void addValue(T value) |
| { |
| currentIndex = ((currentIndex + 1) % bufferSize); |
| if (valid == false && currentIndex % bufferSize == 0) |
| valid = true; |
| |
| // Only update the cached median value when we have to, that |
| // is when the new value is on then other side of the median |
| // compared to the current value at the index. |
| const T currentIndexValue = values[currentIndex]; |
| if ((currentIndexValue > currentMedian && currentMedian > value) |
| || (currentMedian > currentIndexValue && value > currentMedian)) { |
| dirty = true; |
| } |
| |
| values[currentIndex] = value; |
| } |
| |
| bool isMedianValid() const |
| { |
| return valid; |
| } |
| |
| T median() |
| { |
| if (dirty) { |
| dirty = false; |
| |
| // This is a workaround for http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58800 |
| // Avoid using std::nth_element for the affected stdlibc++ releases 4.7.3 and 4.8.2. |
| // Note that the official __GLIBCXX__ value of the releases is not used since that |
| // one might be patched on some GNU/Linux distributions. |
| #if defined(__GLIBCXX__) && __GLIBCXX__ <= 20140107 |
| QVector<T> sorted = values; |
| std::sort(sorted.begin(), sorted.end()); |
| currentMedian = sorted.at(bufferSize / 2); |
| #else |
| QVector<T> copy = values; |
| typename QVector<T>::iterator begin = copy.begin(), mid = copy.begin() + bufferSize/2, end = copy.end(); |
| std::nth_element(begin, mid, end); |
| currentMedian = *mid; |
| #endif |
| } |
| return currentMedian; |
| } |
| private: |
| QVector<T> values; |
| T currentMedian; |
| int bufferSize; |
| int currentIndex; |
| bool valid; |
| bool dirty; |
| }; |
| |
| } // namespace QtConcurrent |
| |
| #endif //Q_QDOC |
| |
| QT_END_NAMESPACE |
| |
| #endif // QT_NO_CONCURRENT |
| |
| #endif |