Hello, At p578 of the standard, MPI_T_PVAR_HANDLE_ALLOC(session, pvar_index, obj_handle, handle, count) ... OUT count number of elements used to represent this variable (integer) It looks to me that pvar can have different classes, e.g., MPI_T_PVAR_CLASS_COUNTER, and datatypes, e.g., MPI_UNSIGNED. And a pvar can be an array (of length *count)* of such datatypes. I guess the common case is count=1. Is my understanding correct? Thanks --Junchao Zhang