Deleting QChart Causes 30+ Second Application Hang!
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@JoeCFD
I am hoping he will (a) try my code and see the time for him, (b) criticise my code if I have done anything wrong (like a leak) and then (c) compare against whatever else he is doing if different. -
@FleetingMemory
Well I don't find anything like you do. Here is a sample I think you should try:#ifndef WIDGET_H #define WIDGET_H #include <QtCharts> #include <QWidget> class Widget : public QWidget { Q_OBJECT public: Widget(QWidget *parent = nullptr); ~Widget(); private: QChart *chart; QChartView *chartView; private slots: void deleteChart(); }; #endif // WIDGET_H#include <QDebug> #include <QElapsedTimer> #include <QTimer> #include <QVBoxLayout> #include "widget.h" // using namespace QtCharts; Widget::Widget(QWidget *parent) : QWidget(parent) { setGeometry(100, 100, 800, 600); setLayout(new QVBoxLayout); this->chart = new QChart(); this->chartView = new QChartView(chart, this); layout()->addWidget(chartView); chartView->setSizePolicy(QSizePolicy::MinimumExpanding, QSizePolicy::MinimumExpanding); for (int i = 0; i < 10; i++) { QLineSeries* series = new QLineSeries(); for (int x = 0; x < 50000; x++) series->append(x, x * (i + 1)); chart->addSeries(series); } QTimer::singleShot(2000, this, &Widget::deleteChart); } void Widget::deleteChart() { QElapsedTimer elapsed; qDebug() << "Starting to delete"; elapsed.start(); layout()->removeWidget(chartView); delete chart; chart = nullptr; delete chartView; chartView = nullptr; qDebug() << "Finished deleting" << elapsed.elapsed(); } Widget::~Widget() {}500,000 points, 10 series. For me this takes 6 milliseconds to "delete", where you claim 30 seconds! Ubuntu 24.04, VirtualBox slow machine/not nearly as much memory as you, Qt 6.4.2 supplied with Ubuntu. How long does it take you?
Possible it could be slow if compiled for Debug, though that is actually how I ran mine, you might check whether Release makes a huger difference?
@JonB I think its not the number of points in a singular line, but the number of series (lines) in total causing the problem. My times I listed are from running on release.
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@JonB I think its not the number of points in a singular line, but the number of series (lines) in total causing the problem. My times I listed are from running on release.
@FleetingMemory
I asked you to produce a minimal example such as mine but you have not. I said earlier I was guessing 10 series to make 500,000 points. If you want help I don't see why you can't convey the necessary information, no point leaving me to create 10 series I mentioned and then say it's not the right number..... And you could always alter my code to whatever numbers you desire to test..... -
@JonB I think its not the number of points in a singular line, but the number of series (lines) in total causing the problem. My times I listed are from running on release.
@FleetingMemory try to call
removeAllSeries() first. It seems this call will not trigger update of qchart.
and then update,
next delete chart. -
@FleetingMemory try to call
removeAllSeries() first. It seems this call will not trigger update of qchart.
and then update,
next delete chart. -
@JoeCFD Will give this a try and let you know!
@FleetingMemory
In your first post of the steps you have tried you already includedRemoving all series prior to deleting
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Yeah, I am going to retry in release with elapsed() to see what is going on and give more info.
Query Size 450,000 points. Spread across 12,000 series.
populating the series after query takes 2,964 milliseconds
Gets stuck on remove all series (freezes main thread), takes 35,774 milliseconds to remove -
Yeah, I am going to retry in release with elapsed() to see what is going on and give more info.
Query Size 450,000 points. Spread across 12,000 series.
populating the series after query takes 2,964 milliseconds
Gets stuck on remove all series (freezes main thread), takes 35,774 milliseconds to remove@FleetingMemory
Yes please test. OOI how can you expect to display 12,000 series to a user, I just don't get it? -
A little more testing - I used release mode, removed all series from QChart in a QChartView after a new query is run. During this test I re-used the same QChart -- after running removeAllSeries(), I used the points from the query to generate new series and add them to the chart. Points are formatted <millis since epoch, value>. Series have OpenGL turned on in this test.
1: A Query is run, Qlist<Qlist<QPointF>> generated. I return the Query Count
2: If QChart Exists, remove all series (this I timed)
3: for each Qlist<QPointF> generate a new series with replace(), append Axes and insert into chart (this I timed)Query Size 450,000 points. Spread across 12,000 series.
populating 12,000 series after query takes 2.964 s
Gets stuck on remove all 12,000 series (freezes main thread), takes 35.774 seconds to removeQuery Size: 332,000 points
populating 10,600 series: 3.3s
populating 2nd time diff data: 3.4s
removing all series: 25.35s
removing all (2nd time diff data): 25.6sQuery Size: 247,900 points
populating 9300 series: 2.5s
removing all series: 19sQuery Size 250,000
Populating Series: 1.32 s
removing all 8,050 series: 14.33s
removing all 8,050 series (2nd run diff data): 13.4sQuery Size 223,200
Populating 8600 series: 2.4s
populating 8600 series(2nd run diff data): 2s
removing all series: 15.6s
removing all series (2nd run diff data): 15.6sQuery Size: 195,600
populating series: 1.7s
Removing 7820 series: 12.5s
removing all 7820 series (2nd run diff data): 12.9sQuery Size 158,543
populating the series after query: 0.7s
removing all 4,859 series: 4.9sQuery Size 21700
Removing 1240 series: 0.395s
populating series: 0.1sQuery Size: 9,818
populating series: 0.04s
removing all 735 series: 0.045s
removing all 735 series (2nd run diff data): 0.044sPerformance seems to get worse pretty quickly at a non-linear rate
If it helps, I am compiling this as a plugin loaded in a simple main application (though that shouldn't affect things).
I have tried with useOpenGL both on and off. As far as I can tell, it makes little difference.
The fact the removeAll/delete freezes the main thread, which essentially locks up the entire application it is running in is a huge issue for me... -
A little more testing - I used release mode, removed all series from QChart in a QChartView after a new query is run. During this test I re-used the same QChart -- after running removeAllSeries(), I used the points from the query to generate new series and add them to the chart. Points are formatted <millis since epoch, value>. Series have OpenGL turned on in this test.
1: A Query is run, Qlist<Qlist<QPointF>> generated. I return the Query Count
2: If QChart Exists, remove all series (this I timed)
3: for each Qlist<QPointF> generate a new series with replace(), append Axes and insert into chart (this I timed)Query Size 450,000 points. Spread across 12,000 series.
populating 12,000 series after query takes 2.964 s
Gets stuck on remove all 12,000 series (freezes main thread), takes 35.774 seconds to removeQuery Size: 332,000 points
populating 10,600 series: 3.3s
populating 2nd time diff data: 3.4s
removing all series: 25.35s
removing all (2nd time diff data): 25.6sQuery Size: 247,900 points
populating 9300 series: 2.5s
removing all series: 19sQuery Size 250,000
Populating Series: 1.32 s
removing all 8,050 series: 14.33s
removing all 8,050 series (2nd run diff data): 13.4sQuery Size 223,200
Populating 8600 series: 2.4s
populating 8600 series(2nd run diff data): 2s
removing all series: 15.6s
removing all series (2nd run diff data): 15.6sQuery Size: 195,600
populating series: 1.7s
Removing 7820 series: 12.5s
removing all 7820 series (2nd run diff data): 12.9sQuery Size 158,543
populating the series after query: 0.7s
removing all 4,859 series: 4.9sQuery Size 21700
Removing 1240 series: 0.395s
populating series: 0.1sQuery Size: 9,818
populating series: 0.04s
removing all 735 series: 0.045s
removing all 735 series (2nd run diff data): 0.044sPerformance seems to get worse pretty quickly at a non-linear rate
If it helps, I am compiling this as a plugin loaded in a simple main application (though that shouldn't affect things).
I have tried with useOpenGL both on and off. As far as I can tell, it makes little difference.
The fact the removeAll/delete freezes the main thread, which essentially locks up the entire application it is running in is a huge issue for me...@FleetingMemory
look at source code here.
https://codebrowser.dev/qt5/qtcharts/src/charts/qchart.cpp.html
removeAllSeries func has a loop to call removeSeries(QAbstractSeries *series)
I guess it will trigger update for each removal. This is not efficient. -
A little more testing - I used release mode, removed all series from QChart in a QChartView after a new query is run. During this test I re-used the same QChart -- after running removeAllSeries(), I used the points from the query to generate new series and add them to the chart. Points are formatted <millis since epoch, value>. Series have OpenGL turned on in this test.
1: A Query is run, Qlist<Qlist<QPointF>> generated. I return the Query Count
2: If QChart Exists, remove all series (this I timed)
3: for each Qlist<QPointF> generate a new series with replace(), append Axes and insert into chart (this I timed)Query Size 450,000 points. Spread across 12,000 series.
populating 12,000 series after query takes 2.964 s
Gets stuck on remove all 12,000 series (freezes main thread), takes 35.774 seconds to removeQuery Size: 332,000 points
populating 10,600 series: 3.3s
populating 2nd time diff data: 3.4s
removing all series: 25.35s
removing all (2nd time diff data): 25.6sQuery Size: 247,900 points
populating 9300 series: 2.5s
removing all series: 19sQuery Size 250,000
Populating Series: 1.32 s
removing all 8,050 series: 14.33s
removing all 8,050 series (2nd run diff data): 13.4sQuery Size 223,200
Populating 8600 series: 2.4s
populating 8600 series(2nd run diff data): 2s
removing all series: 15.6s
removing all series (2nd run diff data): 15.6sQuery Size: 195,600
populating series: 1.7s
Removing 7820 series: 12.5s
removing all 7820 series (2nd run diff data): 12.9sQuery Size 158,543
populating the series after query: 0.7s
removing all 4,859 series: 4.9sQuery Size 21700
Removing 1240 series: 0.395s
populating series: 0.1sQuery Size: 9,818
populating series: 0.04s
removing all 735 series: 0.045s
removing all 735 series (2nd run diff data): 0.044sPerformance seems to get worse pretty quickly at a non-linear rate
If it helps, I am compiling this as a plugin loaded in a simple main application (though that shouldn't affect things).
I have tried with useOpenGL both on and off. As far as I can tell, it makes little difference.
The fact the removeAll/delete freezes the main thread, which essentially locks up the entire application it is running in is a huge issue for me...@FleetingMemory
Why can't you test exactly these figures, with whatever (hopefully tiny) code you use, against the skeleton I provided? You only have to alter the two loop counters. Then people have actual code they can test, so far as I know we really don't know for sure what your code reads. I seem to have been saying/suggesting this all along. If you want people to help, or even to report a bug, we have to have a complete, minimal, reproducible example. -
@FleetingMemory
Well I don't find anything like you do. Here is a sample I think you should try:#ifndef WIDGET_H #define WIDGET_H #include <QtCharts> #include <QWidget> class Widget : public QWidget { Q_OBJECT public: Widget(QWidget *parent = nullptr); ~Widget(); private: QChart *chart; QChartView *chartView; private slots: void deleteChart(); }; #endif // WIDGET_H#include <QDebug> #include <QElapsedTimer> #include <QTimer> #include <QVBoxLayout> #include "widget.h" // using namespace QtCharts; Widget::Widget(QWidget *parent) : QWidget(parent) { setGeometry(100, 100, 800, 600); setLayout(new QVBoxLayout); this->chart = new QChart(); this->chartView = new QChartView(chart, this); layout()->addWidget(chartView); chartView->setSizePolicy(QSizePolicy::MinimumExpanding, QSizePolicy::MinimumExpanding); for (int i = 0; i < 10; i++) { QLineSeries* series = new QLineSeries(); for (int x = 0; x < 50000; x++) series->append(x, x * (i + 1)); chart->addSeries(series); } QTimer::singleShot(2000, this, &Widget::deleteChart); } void Widget::deleteChart() { QElapsedTimer elapsed; qDebug() << "Starting to delete"; elapsed.start(); layout()->removeWidget(chartView); delete chart; chart = nullptr; delete chartView; chartView = nullptr; qDebug() << "Finished deleting" << elapsed.elapsed(); } Widget::~Widget() {}500,000 points, 10 series. For me this takes 6 milliseconds to "delete", where you claim 30 seconds! Ubuntu 24.04, VirtualBox slow machine/not nearly as much memory as you, Qt 6.4.2 supplied with Ubuntu. How long does it take you?
Possible it could be slow if compiled for Debug, though that is actually how I ran mine, you might check whether Release makes a huger difference?
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@JonB I just tried your loop. I get similar results when increasing series count.
@FleetingMemory I tried Jon's code with 10000 series + 10 points and tried different things:
- disable update of QChartView
- disable QChartView and QChart
- hide QChartView and QChart
before chart is deleted. Nothing helps.
However, I am able to get quick clean-up of qchartview with
chartView->setChart( new QChart() ); chart->deleteLater();Not sure if this helps you. If this piece of code does not help, you may try to delete the chart in a thread while charview is available for other uses. I guess your app will have issue at exit.
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@FleetingMemory I tried Jon's code with 10000 series + 10 points and tried different things:
- disable update of QChartView
- disable QChartView and QChart
- hide QChartView and QChart
before chart is deleted. Nothing helps.
However, I am able to get quick clean-up of qchartview with
chartView->setChart( new QChart() ); chart->deleteLater();Not sure if this helps you. If this piece of code does not help, you may try to delete the chart in a thread while charview is available for other uses. I guess your app will have issue at exit.
This post is deleted! -
@FleetingMemory I tried Jon's code with 10000 series + 10 points and tried different things:
- disable update of QChartView
- disable QChartView and QChart
- hide QChartView and QChart
before chart is deleted. Nothing helps.
However, I am able to get quick clean-up of qchartview with
chartView->setChart( new QChart() ); chart->deleteLater();Not sure if this helps you. If this piece of code does not help, you may try to delete the chart in a thread while charview is available for other uses. I guess your app will have issue at exit.
@JoeCFD I tried that as well, it is marginally faster to delete this way than removeAll. I have tried threading but because QChart calls GUI functions, I was not able to get it to work. I tried threading the delete as well as the removal of Series. Neither works. I usually run into errors like -- widget cannot be moved to a new thread -- accessing widget from wrong thread (usually pertains to the QChartData) -- sending signal accross thread, which results in an immediate crash. This is because the removeALLSeries and delete call on update()
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Hi,
Did you try calling setUpdateEnabled(false) on the chart ?
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Hi,
Did you try calling setUpdateEnabled(false) on the chart ?
@SGaist QChart does not have updatesEnabled(false) only QChartView. Doesn't seem to make a difference. I also tried blocking signals.
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@JoeCFD I tried that as well, it is marginally faster to delete this way than removeAll. I have tried threading but because QChart calls GUI functions, I was not able to get it to work. I tried threading the delete as well as the removal of Series. Neither works. I usually run into errors like -- widget cannot be moved to a new thread -- accessing widget from wrong thread (usually pertains to the QChartData) -- sending signal accross thread, which results in an immediate crash. This is because the removeALLSeries and delete call on update()
@FleetingMemory My results with Jon's code:
- use deleteLater
Starting to delete
Finished deleting 771 - original deletion
Starting to delete
Finished deleting 11663
Qt 6.8.2 + Ubuntu 22.04
- use deleteLater
