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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 MedianSize = 7
53};
54
55static qint64 getticks()
56{
57 return QDeadlineTimer::current(timerType: Qt::PreciseTimer).deadlineNSecs();
58}
59
60static double elapsed(qint64 after, qint64 before)
61{
62 return double(after - before);
63}
64
65namespace QtConcurrent {
66
67/*!
68 \class QtConcurrent::Median
69 \inmodule QtConcurrent
70 \internal
71 */
72
73/*!
74 \class QtConcurrent::MedianDouble
75 \inmodule QtConcurrent
76 \internal
77 */
78
79/*!
80 \class QtConcurrent::BlockSizeManager
81 \inmodule QtConcurrent
82 \internal
83 */
84
85/*!
86 \class QtConcurrent::BlockSizeManagerV2
87 \inmodule QtConcurrent
88 \internal
89 */
90
91/*!
92 \class QtConcurrent::ResultReporter
93 \inmodule QtConcurrent
94 \internal
95 */
96
97/*! \fn bool QtConcurrent::selectIteration(std::bidirectional_iterator_tag)
98 \internal
99 */
100
101/*! \fn bool QtConcurrent::selectIteration(std::forward_iterator_tag)
102 \internal
103 */
104
105/*! \fn bool QtConcurrent::selectIteration(std::random_access_iterator_tag)
106 \internal
107 */
108
109/*!
110 \class QtConcurrent::IterateKernel
111 \inmodule QtConcurrent
112 \internal
113 */
114
115/*! \internal
116
117*/
118BlockSizeManager::BlockSizeManager(int iterationCount)
119: maxBlockSize(iterationCount / (QThreadPool::globalInstance()->maxThreadCount() * 2)),
120 beforeUser(0), afterUser(0),
121 controlPartElapsed(MedianSize), userPartElapsed(MedianSize),
122 m_blockSize(1)
123{ }
124
125// Records the time before user code.
126void BlockSizeManager::timeBeforeUser()
127{
128 if (blockSizeMaxed())
129 return;
130
131 beforeUser = getticks();
132 controlPartElapsed.addValue(value: elapsed(after: beforeUser, before: afterUser));
133}
134
135 // Records the time after user code and adjust the block size if we are spending
136 // to much time in the for control code compared with the user code.
137void BlockSizeManager::timeAfterUser()
138{
139 if (blockSizeMaxed())
140 return;
141
142 afterUser = getticks();
143 userPartElapsed.addValue(value: elapsed(after: afterUser, before: beforeUser));
144
145 if (controlPartElapsed.isMedianValid() == false)
146 return;
147
148 if (controlPartElapsed.median() * TargetRatio < userPartElapsed.median())
149 return;
150
151 m_blockSize = qMin(a: m_blockSize * 2, b: maxBlockSize);
152
153#ifdef QTCONCURRENT_FOR_DEBUG
154 qDebug() << QThread::currentThread() << "adjusting block size" << controlPartElapsed.median() << userPartElapsed.median() << m_blockSize;
155#endif
156
157 // Reset the medians after adjusting the block size so we get
158 // new measurements with the new block size.
159 controlPartElapsed.reset();
160 userPartElapsed.reset();
161}
162
163int BlockSizeManager::blockSize()
164{
165 return m_blockSize;
166}
167
168/*! \internal
169
170*/
171BlockSizeManagerV2::BlockSizeManagerV2(int iterationCount)
172 : maxBlockSize(iterationCount / (QThreadPool::globalInstance()->maxThreadCount() * 2)),
173 beforeUser(0), afterUser(0),
174 m_blockSize(1)
175{ }
176
177// Records the time before user code.
178void BlockSizeManagerV2::timeBeforeUser()
179{
180 if (blockSizeMaxed())
181 return;
182
183 beforeUser = getticks();
184 controlPartElapsed.addValue(value: elapsed(after: beforeUser, before: afterUser));
185}
186
187 // Records the time after user code and adjust the block size if we are spending
188 // to much time in the for control code compared with the user code.
189void BlockSizeManagerV2::timeAfterUser()
190{
191 if (blockSizeMaxed())
192 return;
193
194 afterUser = getticks();
195 userPartElapsed.addValue(value: elapsed(after: afterUser, before: beforeUser));
196
197 if (controlPartElapsed.isMedianValid() == false)
198 return;
199
200 if (controlPartElapsed.median() * TargetRatio < userPartElapsed.median())
201 return;
202
203 m_blockSize = qMin(a: m_blockSize * 2, b: maxBlockSize);
204
205#ifdef QTCONCURRENT_FOR_DEBUG
206 qDebug() << QThread::currentThread() << "adjusting block size" << controlPartElapsed.median() << userPartElapsed.median() << m_blockSize;
207#endif
208
209 // Reset the medians after adjusting the block size so we get
210 // new measurements with the new block size.
211 controlPartElapsed.reset();
212 userPartElapsed.reset();
213}
214
215int BlockSizeManagerV2::blockSize()
216{
217 return m_blockSize;
218}
219
220} // namespace QtConcurrent
221
222QT_END_NAMESPACE
223
224#endif // QT_NO_CONCURRENT
225

source code of qtbase/src/concurrent/qtconcurrentiteratekernel.cpp