在我的程序中,我正在从文本文件中读取大量数据。把它放到QTableWidget。 最初它都是在GUI线程&然后我决定多线程它有更好的性能。但相反,性能显着缓慢,即慢8倍! 所以我决定对它进行基准测试。这是我的文件:
的main.cpp
#include <QtGui/QApplication>
#include <QMutex>
#include <QDir>
#include <string>
#include <QDebug>
#include "mainwindow.h"
QFile *logFile = NULL;
QTextStream *logStream = NULL;
QMutex *mutex = NULL;
bool *debugMode = NULL;
void myMessageOutput(QtMsgType type, const char *msg)
{
if(((logFile != NULL) && (debugMode != NULL)))
{
mutex->lock();
switch (type)
{
case QtDebugMsg:
if(!*debugMode)
{
mutex->unlock();
return;
}
*logStream << msg;
logStream->flush();
break;
case QtWarningMsg:
*logStream << "\n*** Warning ***\n";
*logStream << msg;
*logStream << "\n*** Warning Complete ***\n";
logStream->flush();
break;
case QtCriticalMsg:
*logStream << "\n*** Critical ***\n";
*logStream << msg;
*logStream << "\n*** Critical Complete ***\n";
logStream->flush();
break;
case QtFatalMsg:
*logStream << "\n*** Fatal ***\n";
*logStream << msg;
*logStream << "\n*** Fatal Complete ***\n";
logStream->flush();
abort();
}
mutex->unlock();
}
}
void CreateLogFile()
{
QString path = "C:\\Users\\abcd\\Documents\\QT\\benchmark\\output.log";
QFile *file = new QFile(path);
if(file->exists())
file->remove();
if(!file->open(QFile::WriteOnly | QFile::Text))
{
qFatal("Could not create log file.");
}
logStream = new QTextStream(file);
logStream->setRealNumberNotation(QTextStream::FixedNotation);
logStream->setRealNumberPrecision(16);
logFile = file;
}
int main(int argc, char *argv[])
{
mutex = new QMutex();
qInstallMsgHandler(myMessageOutput);
debugMode = new bool;
CreateLogFile();
*debugMode = true;
QApplication a(argc, argv);
MainWindow w;
w.show();
w.bench2();
return a.exec();
}
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QThread>
#include "multi_thread.h"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
void bench2();
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QDebug>
#include <QList>
#include <QTime>
MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new Ui::MainWindow)
{
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::bench2()
{
QTableWidget *table = new QTableWidget();
table->setRowCount(1000);
table->setColumnCount(1000);
for(int i = 0; i < 1000; i++)
{
for(int j = 0; j < 1000; j++)
table->setItem(i, j, new QTableWidgetItem());
}
Multi_Thread **multis = new Multi_Thread *[4];
QThread **thrs = new QThread *[4];
int from;
int to = -1;
QTime time;
time.start();
for(int i = 0; i < 4; i++)
{
from = to + 1;
to = from + 250;
if(i == 3)
to = 999;
multis[i] = new Multi_Thread();
multis[i]->setTable(table, from, to);
thrs[i] = new QThread();
connect(thrs[i], SIGNAL(started()), multis[i], SLOT(bench2_1()));
multis[i]->moveToThread(thrs[i]);
}
for(int i = 0; i < 4; i++)
{
if(!i)
time.start();
thrs[i]->start();
}
for(int i = 0; i < 4; i++)
{
thrs[i]->wait();
}
qDebug() << "\nbench2 1 " << time.elapsed();
for(int i = 0; i < 4; i++)
{
delete multis[i];
delete thrs[i];
}
delete[] multis;
delete[] thrs;
table->clear();
table->setRowCount(1000);
table->setColumnCount(1000);
for(int i = 0; i < 1000; i++)
{
for(int j = 0; j < 1000; j++)
table->setItem(i, j, new QTableWidgetItem());
}
time.start();
for(int i = 0; i < 1000; i++)
{
for(int j = 0; j < 1000; j++)
table->item(i, j)->setText("0");
}
qDebug() << "\nbench2 2 " << time.elapsed();
table->clear();
table->setRowCount(1000);
table->setColumnCount(1000);
QTableWidgetItem ***items = new QTableWidgetItem **[1000];
for(int i = 0; i < 1000; i++)
{
items[i] = new QTableWidgetItem *[1000];
for(int j = 0; j < 1000; j++)
{
QTableWidgetItem *item = new QTableWidgetItem();
table->setItem(i, j, item);
items[i][j] = item;
}
}
multis = new Multi_Thread *[4];
thrs = new QThread *[4];
to = -1;
for(int i = 0; i < 4; i++)
{
from = to + 1;
to = from + 250;
if(i == 3)
to = 999;
multis[i] = new Multi_Thread();
multis[i]->setItems(items, from, to);
thrs[i] = new QThread();
connect(thrs[i], SIGNAL(started()), multis[i], SLOT(bench2_2()));
multis[i]->moveToThread(thrs[i]);
}
table->blockSignals(true);
table->setUpdatesEnabled(false);
table->setWordWrap(false);
for(int i = 0; i < 4; i++)
{
if(!i)
time.start();
thrs[i]->start();
}
for(int i = 0; i < 4; i++)
{
thrs[i]->wait();
}
qDebug() << "\nbench2 3 " << time.elapsed();
table->blockSignals(false);
table->setUpdatesEnabled(true);
table->setWordWrap(true);
for(int i = 0; i < 4; i++)
{
delete multis[i];
delete thrs[i];
}
delete[] multis;
delete[] thrs;
table->clear();
for(int i = 0; i < 1000; i++)
{
delete[] items[i];
}
delete[] items;
}
multi_thread.h
#ifndef MULTI_THREAD_H
#define MULTI_THREAD_H
#include <QObject>
#include <QThread>
#include <QTableWidget>
class Multi_Thread : public QObject
{
Q_OBJECT
public:
explicit Multi_Thread();
void setTable(QTableWidget *tab, int f, int t);
void setItems(QTableWidgetItem ***i, int f, int t);
private:
QTableWidget *table;
QTableWidgetItem ***items;
int from;
int to;
signals:
public slots:
void bench2_1();
void bench2_2();
};
#endif // MULTI_THREAD_H
multi_thread.cpp
#include "multi_thread.h"
Multi_Thread::Multi_Thread() : QObject()
{
}
void Multi_Thread::setTable(QTableWidget *tab, int f, int t)
{
table = tab;
from = f;
to = t;
}
void Multi_Thread::setItems(QTableWidgetItem ***i, int f, int t)
{
items = i;
from = f;
to = t;
}
void Multi_Thread::bench2_1()
{
for(int i = from; i <= to; i++)
{
for(int j = 0; j < 1000; j++)
{
table->item(i, j)->setText("0");
}
}
QThread::currentThread()->exit(0);
}
void Multi_Thread::bench2_2()
{
for(int i = from; i <= to; i++)
{
for(int j = 0; j < 1000; j++)
{
items[i][j]->setText("0");
}
}
QThread::currentThread()->exit(0);
}
output.log
bench2 1 7654
bench2 2 1160
bench2 3 8021
奇怪的是,我期待“bench2 3”比“bench2 1”更快。
PS:我的笔记本电脑硬件需要4个线程才能达到100%的使用率。请根据您的硬件要求进行编辑。可以从环境变量中获知。
答案 0 :(得分:2)
This answer有一个不同的策略,可以非常有效地将大量数据(时间和内存)输入QTableView。我还为同一行的连续请求缓存了已解析的数据行。
答案 1 :(得分:2)
从GUI线程以外的任何线程调用table->item(...)->setText()
是未定义的行为。不要这样做。很高兴你在QObject
中使用QThread
来完成这项工作,但是你不能直接在其他线程中的对象上调用方法。
内部模型将为您的每个更新调用视图的dataChanged()
插槽。除了每个项目的内存分配外,这可能是减速的原因。
在单独的线程中准备数据模型的典型方法是:
在单独的线程中实例化模型。此时,模型尚未连接到任何视图。使用数据初始化模型。它可以是QStandardItemModel
或自定义模型。自定义模型并不那么难,如果您不需要为每个项目执行内存分配,则通常可以提高效率。
将模型连接到视图(QTableView
,而不是QTableWidget
)。为方便起见,您可以将其移动到gui线程,尽管您不必这样做。
仅从其所在的线程访问模型,除非您使用排队的方法调用或排队的信号槽连接。视图使用后者,因此可以存在于与模型分离的线程中。
QTableWidget
将内部QStandardItemModel
与QTableView
捆绑在一起。如果要单独处理模型,只需从视图类中单独使用模型类。