C++ 如何从计算线程到GUI线程获取结果-我需要QSharedMemory吗?
我需要两个线程(主线程(GUI)和计算线程)之间的共享接口。在启动期间,主线程将所有信号存储在C++ 如何从计算线程到GUI线程获取结果-我需要QSharedMemory吗?,c++,qt,C++,Qt,我需要两个线程(主线程(GUI)和计算线程)之间的共享接口。在启动期间,主线程将所有信号存储在QHash()中。第二个线程在每个计算步骤中写入键/值。我应该将它们存储在QSharedMemory中吗 我的应用程序有两个线程。GUI线程和计算线程。用户可以通过GUI以快速模式或实时模式启动模拟。计算随着时间的推移而演变模拟模型。它们的速度足够快,可以比实时更快地执行。如果插入延迟,它们可以保持实时速度,如在游戏或动画中 计算线程应在以下四种模式之一中执行计算: 快速模式:计算无延迟完成,模型演化速
QHash()
中。第二个线程在每个计算步骤中写入键/值。我应该将它们存储在QSharedMemory
中吗
我的应用程序有两个线程。GUI线程和计算线程。用户可以通过GUI以快速模式或实时模式启动模拟。计算随着时间的推移而演变模拟模型。它们的速度足够快,可以比实时更快地执行。如果插入延迟,它们可以保持实时速度,如在游戏或动画中
计算线程应在以下四种模式之一中执行计算:
在线程运行中实现的,而(…){…run_ComputeFunction()…}
run\u ComputeFunction()
实现的为了以防万一您还没有遇到它,Qt提供了一个QSharedMemory示例,可以让您从正确的方向开始: QThread文档还将有助于:
如果您仍然无法回答问题,您可以随时用最少的代码示例更新您的问题。为了防止您还没有遇到问题,Qt提供了一个QSharedMemory示例,可以让您从正确的方向开始: QThread文档还将有助于: 如果您仍然被卡住,您可以随时用最少的代码示例更新您的问题。TL;医生:你没有 我需要两个线程(主线程(GUI)和计算线程)之间的共享接口。(强调矿山)
QSharedMemory
仅适用于多处理,而不是多线程。线程的整体思想是,它们就像进程,但共享它们所在进程的所有内存
因此,您的所有线程都可以看到进程可用的所有内存,您根本不需要做任何事情来共享它
您需要确定计算线程是否应该:
计算机
对象为其数据提供随机更新,“模拟”随机持续时间的时间步。它通过睡眠1/4随机选择时间步长的持续时间来阻止随机时间量。因此,它的作用就好像它可以比实时计算数据快4倍
AbstractComputer
采用了这个简单的功能,并在此基础上提供了四种操作模式:单步、实时和快速
根据模拟的时间推移,computeChunk
在一个数据块中执行的计算量设置为m\u notifyPeriod
,此处设置为20ms
在除停止
以外的所有操作模式中,在将控制返回到事件循环之前,始终至少计算单个块,以保持计算线程的响应性。单个计时器用于将控制从事件循环返回到计算机,并安排未来的计算。在实时模式下,如果计算在实时时钟之前,则在适当的时间安排下一次计算,以便实时运行。在快速模式下,计时器设置为零超时,立即从事件循环返回控制以执行另一个计算块。这具有非常低的开销
抽象计算机跟踪累计的模拟时间步(simTime
)
计算机对象在其自己的线程中运行,并对其数据提供定期、随机生成的更新。数据更改通过通知信号指示。
#include <QtWidgets>
#include <random>
class AbstractComputer : public QObject {
Q_OBJECT
Q_PROPERTY (Mode mode READ mode WRITE setMode NOTIFY modeChanged)
Q_PROPERTY (double simTime READ simTime WRITE setSimTime
RESET resetSimTime NOTIFY simTimeChanged)
public:
enum Mode { Stop, Step, RealTime, Fast };
protected:
typedef double Time; ///< units of seconds
/// Performs one computation step and returns the amount of time the simulation has
/// been advanced by. The computation updates one or more parameters in the map, but
/// doesn't signal the updates. The changed parameters are kept in set.
/// This method can change m_mode to Stop to direct the calling code to stop/pause
/// the simulation.
virtual Time compute() = 0;
/// Notifies of accumulated changes and clears the update set.
virtual void notify() = 0 ;
private:
Mode m_mode, m_prevMode;
QBasicTimer m_timer;
QElapsedTimer m_timeBase;
qint64 m_lastNotification; ///< Last m_timeBase at which notification was issued.
Time m_notifyPeriod; ///< Real time period to issue data change notifications at.
Time m_modeSimTime; ///< Simulation time accumulated in current mode.
Time m_simTime; ///< Total simulation time.
/// Computes a chunk of work that amounts to m_notifyPeriod in simulated time
void computeChunk() {
Time t = 0;
do
t += compute();
while (m_mode != Stop && t < m_notifyPeriod);
m_modeSimTime += t;
m_simTime += t;
}
/// Runs computations according to the selected mode. In RealTime and Fast modes,
/// the notifications are issued at least every m_notifyPeriod.
void timerEvent(QTimerEvent * ev) {
if (ev->timerId() != m_timer.timerId()) return;
const Time startSimTime = m_simTime;
const Mode startMode = m_mode;
switch (m_mode) {
case Step:
m_simTime += compute();
m_timer.stop();
m_mode = Stop;
break;
case Stop:
m_timer.stop();
break;
case RealTime:
if (m_prevMode != RealTime) {
m_modeSimTime = 0.0;
m_timeBase.start();
}
computeChunk();
if (m_mode == RealTime) {
int ahead = round(m_modeSimTime * 1000.0 - m_timeBase.elapsed());
if (ahead < 0) ahead = 0;
m_timer.start(ahead, Qt::PreciseTimer, this);
}
break;
case Fast:
if (m_prevMode != Fast) {
m_timeBase.start();
m_lastNotification = 0;
}
do
computeChunk();
while (m_mode == Fast
&& ((m_timeBase.elapsed() - m_lastNotification) < m_notifyPeriod*1000.0));
m_lastNotification = m_timeBase.elapsed();
break;
}
notify();
if (startSimTime != m_simTime) emit simTimeChanged(m_simTime);
if (m_prevMode != m_mode || startMode != m_mode) emit modeChanged(m_mode);
m_prevMode = m_mode;
}
public:
AbstractComputer(QObject * parent = 0) :
QObject(parent), m_mode(Stop), m_prevMode(Stop), m_notifyPeriod(0.02) /* 50 Hz */,
m_simTime(0.0)
{}
Q_SIGNAL void modeChanged(AbstractComputer::Mode mode); // fully qualified type is required by moc
Q_SIGNAL void simTimeChanged(double);
Q_SLOT void setMode(AbstractComputer::Mode mode) { // fully qualified type is required by moc
if (m_mode == mode) return;
m_mode = mode;
if (m_mode != Stop) m_timer.start(0, this); else m_timer.stop();
}
Q_SLOT void stop() { setMode(Stop); }
Mode mode() const { return m_mode; }
double simTime() const { return m_simTime; }
void setSimTime(double t) { if (m_simTime != t) { m_simTime = t; emit simTimeChanged(t); } }
void resetSimTime() { setSimTime(0.0); }
};
Q_DECLARE_METATYPE(AbstractComputer::Mode)
class Computer : public AbstractComputer {
Q_OBJECT
public:
typedef QHash<QString, double> Map;
private:
typedef QSet<QString> Set;
std::default_random_engine m_eng;
Map m_data;
Set m_updates;
Time compute() Q_DECL_OVERRIDE {
// Update one randomly selected parameter.
auto n = std::uniform_int_distribution<int>(0, m_data.size()-1)(m_eng);
auto it = m_data.begin();
std::advance(it, n);
auto val = std::normal_distribution<double>()(m_eng);
*it = val;
m_updates.insert(it.key());
float tau = std::uniform_real_distribution<float>(0.001, 0.1)(m_eng);
// Pretend that we run ~4x faster than real time
QThread::usleep(tau*1E6/4.0);
return tau;
}
void notify() Q_DECL_OVERRIDE {
for (auto param : m_updates)
emit valueChanged(param, m_data[param]);
m_updates.clear();
}
public:
Computer(const Map & data, QObject * parent = 0) :
AbstractComputer(parent), m_data(data) {}
Map data() const { return m_data; }
Q_SIGNAL void valueChanged(const QString & key, double val);
};
class UI : public QWidget {
Q_OBJECT
QHash<QString, int> m_row;
QStandardItemModel m_model;
QFormLayout m_layout { this };
QTableView m_view;
QComboBox m_mode;
public:
UI(const Computer * computer, QWidget * parent = 0) :
QWidget(parent),
m_model(computer->data().size() + 1, 2, this)
{
auto data = computer->data();
m_mode.addItem("Stop", Computer::Stop);
m_mode.addItem("Step", Computer::Step);
m_mode.addItem("Real Time", Computer::RealTime);
m_mode.addItem("Fast", Computer::Fast);
m_mode.setFocusPolicy(Qt::StrongFocus);
m_view.setFocusPolicy(Qt::NoFocus);
m_layout.addRow(&m_view);
m_layout.addRow("Sim Mode", &m_mode);
m_model.setItem(0, 0, new QStandardItem("Sim Time [s]"));
m_model.setItem(0, 1, new QStandardItem);
int row = 1;
for (auto it = data.begin(); it != data.end(); ++it) {
m_model.setItem(row, 0, new QStandardItem(it.key()));
m_model.setItem(row, 1, new QStandardItem(QString::number(it.value())));
m_row[it.key()] = row++;
}
newMode(computer->mode());
newSimTime(computer->simTime());
m_view.setModel(&m_model);
connect(&m_mode, static_cast<void(QComboBox::*)(int)>(&QComboBox::currentIndexChanged),
[this](int i){
emit modeChanged((AbstractComputer::Mode)m_mode.itemData(i).toInt());
});
}
Q_SIGNAL void modeChanged(AbstractComputer::Mode);
Q_SLOT void newValue(const QString & key, double val) {
m_model.item(m_row[key], 1)->setText(QString::number(val));
}
Q_SLOT void newSimTime(double t) {
m_model.item(0, 1)->setText(QString::number(t));
}
Q_SLOT void newMode(AbstractComputer::Mode mode) {
m_mode.setCurrentIndex(m_mode.findData(mode));
}
};
struct Thread : public QThread { ~Thread() { quit(); wait(); } };
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
qRegisterMetaType<AbstractComputer::Mode>();
Computer::Map init;
init.insert("Foo", 1);
init.insert("Bar", 2);
init.insert("Baz", 3);
Computer computer(init);
QScopedPointer<Thread> thread;
UI ui(&computer);
QObject::connect(&computer, &Computer::valueChanged, &ui, &UI::newValue);
QObject::connect(&computer, &Computer::simTimeChanged, &ui, &UI::newSimTime);
QObject::connect(&computer, &Computer::modeChanged, &ui, &UI::newMode);
QObject::connect(&ui, &UI::modeChanged, &computer, &Computer::setMode);
int threadCount = Thread::idealThreadCount();
if (threadCount == -1 || threadCount > 1) { // Assume a multicore machine
thread.reset(new Thread);
computer.moveToThread(thread.data());
thread->start();
// Prevent the bogus "QBasicTimer::stop: Failed." warnings.
QObject::connect(thread.data(), &QThread::finished, &computer, &Computer::stop);
}
ui.show();
return a.exec();
}
#include "main.moc"