如何用QCustomPlot有效地绘制大的时间序列？ [英] How to plot large time series with QCustomPlot efficiently?

问题描述

我目前正在使用 QCustomPlot 在Qt中绘制数字信号，但似乎当样本数大于10000000时，操作变得非常慢。我有一个时间向量和数据向量，我设置的数据像这样：

  QCustomPlot * plot; 
 QCPGraph * graph; 
 graph-> setData（time，data）;任何机会使这更有效率？
 
 
 
 <因为QCustomPlot在内部使用一个 QCPDataMap （这是一个 typedef   QMap< double，QCPData> ）这意味着它正在使用一个映射来存储按 x  （键）。不幸的是， QCPGraph :: setData（const QVector< double>& x，const QVector< double& y）< / code>方法不利用样本可以并且不使用插入提示，因此这显着改善了结果：
  QCPDataMap * data = new QCPDataMap（）; 
 size_t len = x.size（）; 
 auto xp = std :: begin（x）; 
 auto yp = std :: begin（y）; 
 while（len--）
 data-> insertMulti（data-> constEnd（），* xp，QCPData（* xp ++，* yp ++））; 
 graph-> setData（data）; 
  
我不认为 std :: map  s或 QMap  s是在X，Y图形上存储样本的最佳结构，因为对地图中的每个条目都进行了新的分配和释放，我们正在讨论数百万。 QCustomPlot应该实现一个自定义地图类与自定义分配器，以避免这些内存问题。
 
I am currently plotting a digital signal in Qt with QCustomPlot but it seems that when the number of samples is greater than 10000000 the operation becomes very slow. I have a time vector and a data vector and I'm setting the data like this:
QCustomPlot *plot;
QCPGraph *graph;
graph->setData(time, data); 
Any chance to make this more efficient?
解决方案
Because QCustomPlot uses internally a QCPDataMap (which is a typedef of QMap<double, QCPData>) this means that it is using a map to store the actual data sorted by x coordinates (keys). Unfortunately the QCPGraph::setData(const QVector<double> &x, const QVector<double> &y) method doesn't take advantage of the fact that samples could be ordered and doesn't use the insertion hint, so this improved results significantly:
QCPDataMap *data = new QCPDataMap();
size_t len = x.size();
auto xp = std::begin(x);
auto yp = std::begin(y);
while (len--)
    data->insertMulti(data->constEnd(), *xp, QCPData(*xp++, *yp++)); 
graph->setData(data);
I don't think that std::maps or QMaps is the best structure to store samples on X,Y graphs because a new allocation and release is done for every entry in the map and we are talking about millions of them. QCustomPlot should implement a custom map class with a custom allocator to avoid these memory issues.

                        
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