title: Does MPI_Type_commit implicitly call a barrier on all the processes in MPI_COMM_WORLD?
body: <p>In my code I define a new MPI user-defined data type.
  I was wondering if the MPI_Barrier function must follow the MPI_Commit or must be placed at some point where the first use of the new data type appears so that all the processes acknowledge and agree on the defintion of the new data type.</p>
  
  <p>Thanks.</p>