一、性能测试

最近使用opengl画点云数据时发现比较卡顿，原因是我使用了QList数据结构，后面改为QVector改善很多，速度提升1倍。

private:QVector m_pointVector;void PointCloud3dWidget::drawGL()
{drawGrid();drawCoordinates();glBegin(GL_POINTS);foreach (auto vec3d, m_pointVector){glVertex3d(vec3d.x(), vec3d.y(), vec3d.z());}glEnd();
}

为了探寻哪种数据结构、哪种遍历方式最快，我对QList与QVector分别用小数据量，中数据量，大数据量进行了测试，并且使用了for、foreach、auto、迭代器组合了7种遍历方式做了对比，测试结果如下：

测试代码如下：

void QListTest(QList &pointList)
{qDebug() << "=======QList======";QTime ms;ms.start();/* 方式1：foreach , */foreach (QVector3D vec, pointList){int x = vec.x();int y = vec.y();int z = vec.z();}qDebug() << "foreach ," << ms.elapsed() << "ms";/* 方式2：foreach auto , */ms.restart();foreach (auto vec, pointList){int x = vec.x();int y = vec.y();int z = vec.z();}qDebug() << "foreach auto ," << ms.elapsed() << "ms";/* 方式3：for ;  ;*/ms.restart();for(int i = 0; i < pointList.size() ; ++i){QVector3D vec = pointList.at(i);int x = vec.x();int y = vec.y();int z = vec.z();}qDebug() << "for ;" << ms.elapsed() << "ms";/* 方式4：for : */ms.restart();for(QVector3D vec : pointList){int x = vec.x();int y = vec.y();int z = vec.z();}qDebug() << "for :" << ms.elapsed() << "ms";/* 方式5：for auto : */ms.restart();for(auto vec : pointList){int x = vec.x();int y = vec.y();int z = vec.z();}qDebug() << "for auto :" << ms.elapsed() << "ms";/* 方式6：for iterator */ms.restart();QList::iterator iter;for (iter = pointList.begin(); iter != pointList.end(); iter++){int x = (*iter).x();int y = (*iter).y();int z = (*iter).z();}qDebug() << "iterator" << ms.elapsed() << "ms";/* 方式7：for auto iterator  */ms.restart();for (auto iter = pointList.begin(); iter != pointList.end(); iter++){int x = (*iter).x();int y = (*iter).y();int z = (*iter).z();}qDebug() << "iterator auto" << ms.elapsed() << "ms";
}void QVectorTest(QVector &pointVector)
{qDebug() << "=======QVector======";QTime ms;ms.start();/* 方式1：foreach , */foreach (QVector3D vec, pointVector){int x = vec.x();int y = vec.y();int z = vec.z();}qDebug() << "foreach" << ms.elapsed() << "ms";/* 方式2：foreach auto , */ms.restart();foreach (auto vec, pointVector){int x = vec.x();int y = vec.y();int z = vec.z();}qDebug() << "foreach auto" << ms.elapsed() << "ms";/* 方式3：for ;  ;*/ms.restart();for(int i = 0; i < pointVector.size() ; ++i){QVector3D vec = pointVector.at(i);int x = vec.x();int y = vec.y();int z = vec.z();}qDebug() << "for ;" << ms.elapsed() << "ms";/* 方式4：for : */ms.restart();for(QVector3D vec : pointVector){int x = vec.x();int y = vec.y();int z = vec.z();}qDebug() << "for :" << ms.elapsed() << "ms";/* 方式5：for auto : */ms.restart();for(auto vec : pointVector){int x = vec.x();int y = vec.y();int z = vec.z();}qDebug() << "for auto :" << ms.elapsed() << "ms";/* 方式6：for iterator*/ms.restart();QVector::iterator iter;for (iter = pointVector.begin(); iter != pointVector.end(); iter++){int x = (*iter).x();int y = (*iter).y();int z = (*iter).z();}qDebug() << "iterator" << ms.elapsed() << "ms";/* 方式7：for auto iterator  */ms.restart();for (auto iter = pointVector.begin(); iter != pointVector.end(); iter++){int x = (*iter).x();int y = (*iter).y();int z = (*iter).z();}qDebug() << "iterator auto" << ms.elapsed() << "ms";
}int main()
{QList pointList;QVector pointVector;for(int i = 0; i < 300; ++i){for(int j = 0; j < 300; ++j){pointList.append(QVector3D(i, j, i + j));pointVector.append(QVector3D(i, j, i + j));}}QListTest(pointList);QVectorTest(pointVector);return 0;
}