ros(26):ros::Time::now()，ros::Duration，toSec()，toNSec()； Calculate program execution time

1. ros Time format description

        Time has moments and durations , The duration can be negative , The format is as follows , Divided into seconds and nanoseconds , Conversion relation ：1nsec=1e-9sec.

int32 sec
int32 nsec

2. ros::Time::now()

         Retrieve the current time , It's time .

         If in use ROS Clock time , According to ROS Clock return time . Otherwise, return to the current wall clock time , The wall clock is understood as being in a room / The clock hanging in the environment , No one cares about him / Change it , I understand wall clock time as system time .

3. ros::Duration

        Represents a period of time , It could be negative

4.  toSec()

        I am here ros namespace There was no , Should be c++ Function of , It means that “1 ros Time format description ” The format shown in is converted to seconds

5.  toNSec()

         Convert time or timestamp to nanoseconds

6. Examples of use

Calculate program execution time

    #include <iostream>
    #include "ros/ros.h"

    
    double begin_time = ros::Time::now().toSec();

    double end_time = ros::Time::now().toSec();
    std::cout << " One search takes time :" << (end_time - begin_time) << std::endl;

Reference link ：

ros::Duration  rostime: ros::Duration Class Reference

ros::Time   rostime: ros::Time Class Reference

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