How to verify if all requested MPI ranks are invoked

I am running a simulation using 4 thread-MPI. In the log file, I expected that I would see notifications “Started mdrun on rank 0 …”, " Started mdrun on rank 1…", " Started mdrun on rank 2…", " Started mdrun on rank 3…"
However, only rank 0 is mentioned in the log file: “Started mdrun on rank 0 …”
This is confusing since the mdrun should be started on 4 ranks.

At the end of the log file, there is computing report for the whole 4 ranks. How can I get the report for each rank seperately? Since the log file only reports for the 4 ranks as a whole, I cannot know if all the MPI ranks are invoked properly, or equally busy. Can it happens that even I make a call for 4 t-MPI but one or more t-MPI do nothing and the remaining t-MPI are busy?