/****************************************************************************

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** contained in the Technology Preview License Agreement accompanying

** this package.

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** GNU Lesser General Public License Usage

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** 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

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****************************************************************************/

#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 <qt_windows.h>

#endif

#include "private/qfunctions_p.h"

#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

#ifdef Q_OS_SYMBIAN

    return clock();

#else

    // no clock_gettime(), fall back to wall time

    struct timeval tv;

    gettimeofday(&tv, 0);

    return (tv.tv_sec * 1000000) + tv.tv_usec;

#endif

#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