I have a powerfull cpu, But still get map update warning

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There are plenty of factors that could affect costmap update frequency. In my experience, usually what causes the map update rate to miss the desired rate is either (1) costmap has lots of layers to update, including but not limited to the inflation that needs to be done, and (2) the planner is taking a long time to plan the path. For the former look at reducing the number of updates that needs to be done, and for the latter look at using more efficient planners like a*star planner.

As my knowledge, is related with amcl. It produce very good localization accuracy but if you work on big maps, problem. You should try cartographer, more complex parameters but might be avoid your problem.