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I am trying to run gmapping_slam on some old data to improve the position estimate and during my use of the resulting /map -> /odom I realized the stamp on the transforms were using the current walltime rather than the simulated time.

So I setup an experiment to narrow down the cause of this.

I created two simple examples using ros Time in c++ and python:


#!/usr/bin/env python

import roslib; roslib.load_manifest('time_example')
import rospy

def main():
    r = rospy.Rate(5)
    while not rospy.is_shutdown():
        rospy.loginfo("The time is: %f" % rospy.Time.now().to_sec())

if __name__ == '__main__':


#include "ros/ros.h"

int main(int argc, char **argv) {
  ros::init(argc, argv, "teleop_server");
  ros::NodeHandle n;
  ros::Rate r (5);
  while (ros::ok()) {
    ROS_INFO("The time is: %f", ros::Time::now().toSec());

Then I created a roscore instance:

∫ roscore
... logging to /home/william/.ros/log/1bd2d176-1bd5-11e1-a585-002564acbaae/roslaunch-GDRS-Workstation-16779.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

started roslaunch server http://GDRS-Workstation:53680/
ros_comm version 1.6.5


 * /rosversion
 * /rosdistro


auto-starting new master
process[master]: started with pid [16794]

setting /run_id to 1bd2d176-1bd5-11e1-a585-002564acbaae
process[rosout-1]: started with pid [16807]
started core service [/rosout]

And then in a new terminal I set the use_sim_time parameter with rosparam:

∫ rosparam set use_sim_time 1

In the same terminal I started a bag file I am using.

∫ rosbag play --clock gavlab_and_hallway_2011-04-17-15-09-47.bag 
[ INFO] [1322715599.665805485]: Opening gavlab_and_hallway_2011-04-17-15-09-47.bag

Waiting 0.2 seconds after advertising topics... done.

Hit space to toggle paused, or 's' to step.
 [RUNNING]  Bag Time: 1303070993.265138   Duration: 5.743087 / 715.993344

In a new terminal I ran the Python and then the C++ code:

∫ python nodes/time_example.py 
[INFO] [WallTime: 1322714195.471402] [0.000000] The time is: 0.000000
[INFO] [WallTime: 1322714195.857057] [1303071368.690635] The time is: 1303071368.690635
[INFO] [WallTime: 1322714195.857385] [1303071368.690635] The time is: 1303071368.690635
[INFO] [WallTime: 1322714196.055195] [1303071368.892812] The time is: 1303071368.892812
[INFO] [WallTime: 1322714211.060998] [1303071383.899060] The time is: 1303071383.899060
[INFO] [WallTime: 1322714211.257225] [1303071384.091894] The time is: 1303071384.091894
[INFO] [WallTime: 1322714211.453530] [1303071384.294445] The time is: 1303071384.294445
^CTraceback (most recent call last):
  File "nodes/time_example.py", line 15, in <module>
  File "nodes/time_example.py", line 12, in main
  File "/opt/ros/electric/stacks/ros_comm/clients/rospy/src/rospy/timer.py", line 77, in sleep
    sleep(self.sleep_dur - elapsed)
  File "/opt/ros/electric/stacks/ros_comm/clients/rospy/src/rospy/timer.py", line 132, in sleep
    raise rospy.exceptions.ROSInterruptException("ROS shutdown request")
rospy.exceptions.ROSInterruptException: ROS shutdown request
∫ bin/time_example 
[ INFO] [1322714223.326848478]: The time is: 1322714223.326797
[ INFO] [1322714223.526966411]: The time is: 1322714223.526938
[ INFO] [1322714223.726959496]: The time is: 1322714223.726931
[ INFO] [1322714223.926960677]: The time is: 1322714223.926931
[ INFO] [1322714231.126978724]: The time is: 1322714231.126951
[ INFO] [1322714231.326972936]: The time is: 1322714231.326946
[ INFO] [1322714231.527002318]: The time is: 1322714231.526975
[ INFO] [1322714231.726982139]: The time is: 1322714231.726955

As you can see the Python node is reporting the correct simulated time, and sees the initial time of 0 during the clock initialization period, but the C++ node is reporting the wall time rather than the sim time.

Am I missing something here? Is there another step to make C++ respect the use_sim_time setting?

I am using the latest ROS electric debs on Ubuntu 11.10 x86_64 and I can confirm this is happening on my MacbookPro running the Homebrew based ROS electric source install.

Thanks in advance.

Originally posted by William on ROS Answers with karma: 17335 on 2011-11-30

Post score: 0


1 Answer 1


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So, Python will work with rosparam set use_sim_time 1 but C++ needs rosparam set use_sim_time true. Maybe there should be a warning about this on the wiki or at run time.

Originally posted by William with karma: 17335 on 2011-11-30

This answer was ACCEPTED on the original site

Post score: 4

Original comments

Comment by Mac on 2011-11-30:
That has got to be a bug. If it isn't a bug, it should be. If it shouldn't be a bug, then I need be surgically altered to believe that. I'd open a ticket.

Comment by Dave Coleman on 2014-05-27:
This got me just now, too. Was a ticket ever made?

Comment by William on 2014-05-28:
I guess not, it was before github.

Comment by Dave Coleman on 2014-06-09:
I created a ticket here https://github.com/ros/ros_comm/issues/436


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