Qvector shallow copy performance test

    QTime t0;
    for (int i = 0; i < 100000000; ++i) {
    
        data1.append(i);
    }
    //【1】 The first is appended directly to the tail 
    // The way 1：append
    t0.start();// Start 
    data2.append(data1);
    qDebug()<<"data2 Size "<<data2.size()<<"Append The way : Append to vector; Time is "<<t0.elapsed();
    data2.clear();


    // The way 2:<<
    t0.restart();
    data2<<data1;
    qDebug()<<"data2 Size "<<data2.size()<<"<< The way ： Append to vector; Time is "<<t0.elapsed();
    data2.clear();

    //【2】 The second replication construct   And copy operators 
    // The way 1:qvector(&)
    t0.restart();
    QVector<float> data3(data1);
    qDebug()<<"data2 Size "<<data3.size()<<" Copy construction ; Time is "<<t0.elapsed();

    data2.clear();
    // The way 2:=(&)
    t0.restart();
    data2=data1;
    qDebug()<<"data2 Size "<<data2.size()<<" Copy operation ; Time is "<<t0.elapsed();
    // Transfer parameter assignment 
    t0.restart();
    dodo(data2);
    qDebug()<<"data2 Size "<<data2.size()<<" Copy parameters ( In fact, the copy construct is called ); Time is "<<t0.elapsed();// structure 


    //【3】 swap In exchange for 
    t0.restart();
    data2.swap(data1);
    qDebug()<<"data2 Size "<<data2.size()<<"swap Dafa ; Time is "<<t0.elapsed();


    data2.clear();
    //【4】 Loop assignment   Silly 
    t0.restart();
    for (int i = 0; i < data1.size(); ++i) {
    
        data2.append(data1.at(i));
    }
    qDebug()<<"data2 Size "<<data2.size()<<" Loop assignment ; Time is "<<t0.elapsed();

    //【5】 Copy  , Note that the target array must be kept larger than or equal to the size of the copy array 
    t0.restart();
    memcpy(data2.begin(),data1.begin(),(size_t)sizeof(float)*data1.size()/2);
    qDebug()<<"data2 Size "<<data2.size()<<" Copy memory ; Time is "<<t0.elapsed();

so use swap perhaps append And copy constructs about Shallow copy arrays are much faster .