Details
-
Bug
-
Resolution: Done
-
P2: Important
-
4.7.3
-
None
-
PC Ubuntu + ARM9 Embedded Linux
-
752cd2aca42f6625f1cfc364937e0d39828cf954
Description
Accessing a QVariantMap/QVariantList is very slow in QML.
This applies to every single QVariantMap/QVariantList acess, even if it is the same access. Around 150 ms on ARM9 200MHz.
Accessing a QList<QObject*> is 15 times faster on a ARM9.
Of course, a QList is accessed by indexes and QVariantMap by "string indexes". I could reach an even better access time with "string indexes" by associating a "QHash<QString, int> m_prgVarCode2Idx" and a "QList<QObject > m_sublist". This is 15 times faster than accessing a QList<QObject> and 30 times faster than accessing a QVariantMap:
Q_INVOKABLE QObject* getParameterFromCode(QString code)
{
QObject *retval = NULL;
if (m_prgVarCode2Idx.contains(code))
retval = m_sublist.at(m_prgVarCode2Idx.value(code));
return retval;
}
Let's consider this code
#ifndef PARAMETERTEST_H
#define PARAMETERTEST_H
#include <QtDeclarative>
#include <QObject>
class ParameterCode: public QObject
{
Q_OBJECT
Q_PROPERTY(QString code READ code WRITE setCode NOTIFY notifyChanged);
public:
ParameterCode(QString & code):m_code(code){};
QString &code()
{
return m_code;
}
void setCode(QString code) {
m_code = code;
emit notifyChanged();
}
signals:
void notifyChanged();
private:
QString m_code;
};
class ParameterTest : public QObject
{
Q_OBJECT
Q_PROPERTY(QList<QObject*> sublist READ sublist NOTIFY parametersNotifyChanged)
Q_PROPERTY(QVariantList vsubparams READ vsubparams NOTIFY parametersNotifyChanged)
Q_PROPERTY(QVariantMap variantMapParameters READ variantMapParameters NOTIFY parametersNotifyChanged);
public:
ParameterTest()
{
for (int i = 0; i < 500; i++)
{
QString code("TESTCODE");
code += QString::number(i);
m_prgVarCode2Idx[code] = i;
ParameterCode *newParameter = new ParameterCode(code);
m_vsubparams.append(QVariant::fromValue((QObject*)newParameter));
m_vProgramParameters[code] = QVariant::fromValue((QObject*)newParameter);
m_sublist.append((QObject*)newParameter);
}
}
Q_INVOKABLE QObject* getParameterFromCode(QString code)
{
QObject *retval = NULL;
if (m_prgVarCode2Idx.contains(code))
retval = m_sublist.at(m_prgVarCode2Idx.value(code));
return retval;
}
QVariantList & vsubparams() {
return m_vsubparams;
}
QVariantMap & variantMapParameters()
{
return m_vProgramParameters;
}
QList<QObject*> & sublist() {
return m_sublist;
}
signals:
void parametersNotifyChanged();
private:
QVariantMap m_vProgramParameters;
QVariantList m_vsubparams;
QList<QObject*> m_sublist;
QHash<QString, int> m_prgVarCode2Idx;
};
#endif // PARAMETERTEST_H
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QDeclarativeView *mHomeView = new QDeclarativeView();
QDeclarativeContext *context = mHomeView->rootContext();
context->setContextProperty("parametertest", new ParameterTest());
mHomeView->setSource(QUrl("qrc:/programSelectionPage.qml"));
mHomeView->show();
return a.exec();
}
import QtQuick 1.0
Item {
width: 320
height: 240
focus: true
function test_1() //around 150 msecs per access on arm
{
var inittime = new Date();
var val;
for (var i = 0; i < 10; i++)
val = parametertest.variantMapParameters["TESTCODE50"].code;
var duration = new Date() - inittime;
console.log("1--parameter value:"+ val)
console.log(" called in "+duration+" msecs. ");
}
function test_2() //around 150 msecs per access on arm
{
var inittime = new Date();
var val;
for (var i = 0; i < 10; i++)
val = parametertest.variantMapParameters.TESTCODE50.code;
var duration = new Date() - inittime;
console.log("2--parameter value:"+ val);
console.log(" called in "+duration+" msecs. ");
}
function test_3() //around 125 msecs per access on arm
{
var inittime = new Date();
var val;
for (var i = 0; i < 10; i++)
val = parametertest.vsubparams[50].code;
var duration = new Date() - inittime;
console.log("3--parameter value:"+ val);
console.log(" called in "+duration+" msecs. ");
}
function test_4() //around 9 msecs per access on arm
{
var inittime = new Date();
var val;
for (var i = 0; i < 100; i++)
val = parametertest.sublist[50].code;
var duration = new Date() - inittime;
console.log("4--parameter value:"+ val);
console.log(" called in "+duration+" msecs. ");
}
function test_5() //around 0.6 msecs per access on arm
{
var inittime = new Date();
for (var i = 0; i < 100; i++)
var val = parametertest.getParameterFromCode("TESTCODE50").code;
var duration = new Date() - inittime;
console.log("5--parameter value:"+ val);
console.log(" called in "+duration+" msecs. ");
}
Keys.onPressed:{
test_1();
test_2();
test_3();
test_4();
test_5();
}
}
On a PC:
1--parameter value:TESTCODE50 called in 187 msecs. 2--parameter value:TESTCODE50 called in 197 msecs. 3--parameter value:TESTCODE50 called in 68 msecs. 4--parameter value:TESTCODE50 called in 31 msecs. 5--parameter value:TESTCODE50 called in 4 msecs.
On a ARM9 200MHz:
1--parameter value:TESTCODE50 called in 1439 msecs. 2--parameter value:TESTCODE50 called in 1510 msecs. 3--parameter value:TESTCODE50 called in 1263 msecs. 4--parameter value:TESTCODE50 called in 956 msecs. 5--parameter value:TESTCODE50 called in 57 msecs.
Why is it so slow with a QVariantMap ? It seems the hash table between "string indexes" and indexes are constructed at every single access.