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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 stdlibc++ <= 4.7.3 || (>= 4.8.0 && <= 4.8.2)
#if defined(__GLIBCXX__) && (__GLIBCXX__ <= 20130411 || (__GLIBCXX__ >= 20130322 && __GLIBCXX__ <= 20131016))
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
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