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39
40#include "qtconcurrentiteratekernel.h"
41
42#include <qdeadlinetimer.h>
43#include "private/qfunctions_p.h"
44
45
46#if !defined(QT_NO_CONCURRENT) || defined(Q_CLANG_QDOC)
47
48QT_BEGIN_NAMESPACE
49
50enum {
51 TargetRatio = 100
52};
53
54static qint64 getticks()
55{
56 return QDeadlineTimer::current(Qt::PreciseTimer).deadlineNSecs();
57}
58
59static double elapsed(qint64 after, qint64 before)
60{
61 return double(after - before);
62}
63
64namespace QtConcurrent {
65
66/*!
67 \class QtConcurrent::Median
68 \inmodule QtConcurrent
69 \internal
70 */
71
72/*!
73 \class QtConcurrent::BlockSizeManager
74 \inmodule QtConcurrent
75 \internal
76 */
77
78/*!
79 \class QtConcurrent::ResultReporter
80 \inmodule QtConcurrent
81 \internal
82 */
83
84/*! \fn bool QtConcurrent::selectIteration(std::bidirectional_iterator_tag)
85 \internal
86 */
87
88/*! \fn bool QtConcurrent::selectIteration(std::forward_iterator_tag)
89 \internal
90 */
91
92/*! \fn bool QtConcurrent::selectIteration(std::random_access_iterator_tag)
93 \internal
94 */
95
96/*!
97 \class QtConcurrent::IterateKernel
98 \inmodule QtConcurrent
99 \internal
100 */
101
102/*! \internal
103
104*/
105BlockSizeManager::BlockSizeManager(QThreadPool *pool, int iterationCount)
106 : maxBlockSize(iterationCount / (pool->maxThreadCount() * 2)),
107 beforeUser(0), afterUser(0),
108 m_blockSize(1)
109{ }
110
111// Records the time before user code.
112void BlockSizeManager::timeBeforeUser()
113{
114 if (blockSizeMaxed())
115 return;
116
117 beforeUser = getticks();
118 controlPartElapsed.addValue(elapsed(beforeUser, afterUser));
119}
120
121 // Records the time after user code and adjust the block size if we are spending
122 // to much time in the for control code compared with the user code.
123void BlockSizeManager::timeAfterUser()
124{
125 if (blockSizeMaxed())
126 return;
127
128 afterUser = getticks();
129 userPartElapsed.addValue(elapsed(afterUser, beforeUser));
130
131 if (controlPartElapsed.isMedianValid() == false)
132 return;
133
134 if (controlPartElapsed.median() * int(TargetRatio) < userPartElapsed.median())
135 return;
136
137 m_blockSize = qMin(m_blockSize * 2, maxBlockSize);
138
139#ifdef QTCONCURRENT_FOR_DEBUG
140 qDebug() << QThread::currentThread() << "adjusting block size" << controlPartElapsed.median() << userPartElapsed.median() << m_blockSize;
141#endif
142
143 // Reset the medians after adjusting the block size so we get
144 // new measurements with the new block size.
145 controlPartElapsed.reset();
146 userPartElapsed.reset();
147}
148
149int BlockSizeManager::blockSize()
150{
151 return m_blockSize;
152}
153
154} // namespace QtConcurrent
155
156QT_END_NAMESPACE
157
158#endif // QT_NO_CONCURRENT
159