QT计算函数运行时间，精确到ms和us
1、精度为ms级，利用QTime
#include <QTime>
QTime time;
time.start();
youFunction();
qDebug() << time.elapsed()/1000.0 << "s";
2、精度为us级，利用gettimeofday()
#include <QDebug>
#include <sys/time.h>
struct timeval tpstart,tpend;
float timeUse;
gettimeofday(&tpstart,NULL);
youFunction();
gettimeofday(&tpend,NULL);
timeUse=(1000000*(tpend.tv_sec-tpstart.tv_sec) + tpend.tv_usec-tpstart.tv_usec)/1000000.0;
qDebug() << timeUse << "s";