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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
#include "qtconcurrentiteratekernel.h"
#include <qdeadlinetimer.h>
#include "private/qfunctions_p.h"
#if !defined(QT_NO_CONCURRENT) || defined(Q_CLANG_QDOC)
QT_BEGIN_NAMESPACE
enum {
TargetRatio = 100
};
static qint64 getticks()
{
return QDeadlineTimer::current(Qt::PreciseTimer).deadlineNSecs();
}
static double elapsed(qint64 after, qint64 before)
{
return double(after - before);
}
namespace QtConcurrent {
/*!
\class QtConcurrent::Median
\inmodule QtConcurrent
\internal
*/
/*!
\class QtConcurrent::BlockSizeManager
\inmodule QtConcurrent
\internal
*/
/*!
\class QtConcurrent::ResultReporter
\inmodule QtConcurrent
\internal
*/
/*! \fn bool QtConcurrent::selectIteration(std::bidirectional_iterator_tag)
\internal
*/
/*! \fn bool QtConcurrent::selectIteration(std::forward_iterator_tag)
\internal
*/
/*! \fn bool QtConcurrent::selectIteration(std::random_access_iterator_tag)
\internal
*/
/*!
\class QtConcurrent::IterateKernel
\inmodule QtConcurrent
\internal
*/
/*! \internal
*/
BlockSizeManager::BlockSizeManager(QThreadPool *pool, int iterationCount)
: maxBlockSize(iterationCount / (pool->maxThreadCount() * 2)),
beforeUser(0), afterUser(0),
m_blockSize(1)
{ }
// Records the time before user code.
void BlockSizeManager::timeBeforeUser()
{
if (blockSizeMaxed())
return;
beforeUser = getticks();
controlPartElapsed.addValue(elapsed(beforeUser, afterUser));
}
// Records the time after user code and adjust the block size if we are spending
// to much time in the for control code compared with the user code.
void BlockSizeManager::timeAfterUser()
{
if (blockSizeMaxed())
return;
afterUser = getticks();
userPartElapsed.addValue(elapsed(afterUser, beforeUser));
if (controlPartElapsed.isMedianValid() == false)
return;
if (controlPartElapsed.median() * int(TargetRatio) < userPartElapsed.median())
return;
m_blockSize = qMin(m_blockSize * 2, maxBlockSize);
#ifdef QTCONCURRENT_FOR_DEBUG
qDebug() << QThread::currentThread() << "adjusting block size" << controlPartElapsed.median() << userPartElapsed.median() << m_blockSize;
#endif
// Reset the medians after adjusting the block size so we get
// new measurements with the new block size.
controlPartElapsed.reset();
userPartElapsed.reset();
}
int BlockSizeManager::blockSize()
{
return m_blockSize;
}
} // namespace QtConcurrent
QT_END_NAMESPACE
#endif // QT_NO_CONCURRENT
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