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/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** 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.
**
**
**
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include "qtconcurrentiteratekernel.h"
#if defined(Q_OS_MAC)
#include <mach/mach.h>
#include <mach/mach_time.h>
#include <unistd.h>
#elif defined(Q_OS_UNIX)
#include <time.h>
#include <unistd.h>
#elif defined(Q_OS_WIN)
#include <windows.h>
#endif
#ifndef QT_NO_CONCURRENT
QT_BEGIN_NAMESPACE
enum {
TargetRatio = 100,
MedianSize = 7
};
#if defined(Q_OS_MAC)
static qint64 getticks()
{
return mach_absolute_time();
}
#elif defined(Q_OS_UNIX)
static qint64 getticks()
{
#if defined(_POSIX_TIMERS) && (_POSIX_TIMERS > 0)
clockid_t clockId;
#ifndef _POSIX_THREAD_CPUTIME
clockId = CLOCK_REALTIME;
#elif (_POSIX_THREAD_CPUTIME-0 <= 0)
// if we don't have CLOCK_THREAD_CPUTIME_ID, we have to just use elapsed realtime instead
clockId = CLOCK_REALTIME;
# if (_POSIX_THREAD_CPUTIME-0 == 0)
// detect availablility of CLOCK_THREAD_CPUTIME_ID
static long useThreadCpuTime = -2;
if (useThreadCpuTime == -2) {
// sysconf() will return either -1 or _POSIX_VERSION (don't care about thread races here)
useThreadCpuTime = sysconf(_SC_THREAD_CPUTIME);
}
if (useThreadCpuTime != -1)
clockId = CLOCK_THREAD_CPUTIME_ID;
# endif
#else
clockId = CLOCK_THREAD_CPUTIME_ID;
#endif
struct timespec ts;
if (clock_gettime(clockId, &ts) == -1)
return 0;
return (ts.tv_sec * 1000000000) + ts.tv_nsec;
#else
// no clock_gettime(), fall back to wall time
struct timeval tv;
gettimeofday(&tv, 0);
return (tv.tv_sec * 1000000) + tv.tv_usec;
#endif
}
#elif defined(Q_OS_WIN)
static qint64 getticks()
{
LARGE_INTEGER x;
if (!QueryPerformanceCounter(&x))
return 0;
return x.QuadPart;
}
#endif
static double elapsed(qint64 after, qint64 before)
{
return double(after - before);
}
namespace QtConcurrent {
/*! \internal
*/
BlockSizeManager::BlockSizeManager(int iterationCount)
: maxBlockSize(iterationCount / (QThreadPool::globalInstance()->maxThreadCount() * 2)),
beforeUser(0), afterUser(0),
controlPartElapsed(MedianSize), userPartElapsed(MedianSize),
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() * 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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