MPI\_TYPE\_UB(3) Open MPI MPI\_TYPE\_UB(3) MPI\_Type\_ub — Returns the upper bound of a datatype — this routine is deprecated in favor of MPI\_Type\_get\_extent <#mpi-type-get-extent>. # [SYNTAX](#SYNTAX) ## [C Syntax](#C_Syntax) ``` #include int MPI_Type_ub(MPI_Datatype datatype, MPI_Aint *displacement) ``` ## [Fortran Syntax](#Fortran_Syntax) ``` USE MPI ! or the older form: INCLUDE 'mpif.h' MPI_TYPE_UB(DATATYPE, DISPLACEMENT, IERROR) INTEGER DATATYPE, DISPLACEMENT, IERROR ``` # [INPUT PARAMETER](#INPUT_PARAMETER) • **datatype**: Datatype (handle). # [OUTPUT PARAMETERS](#OUTPUT_PARAMETERS) - **displacement**: Displacement of upper bound from origin, in bytes (integer). - **ierror**: Fortran only: Error status (integer). # [DESCRIPTION](#DESCRIPTION) Note that use of this routine is *deprecated* as of MPI-2. Please use MPI\_Type\_get\_extent <#mpi-type-get-extent> instead. MPI\_Type\_ub returns the upper bound of a data type. This will differ from zero if the type was constructed using MPI\_UB. The upper bound will take into account any alignment considerations. The “pseudo-datatypes,” MPI\_LB and MPI\_UB, can be used, respectively, to mark the upper bound (or the lower bound) of a datatype. These pseudo-datatypes occupy no space (extent (MPI\_LB) = extent (MPI\_UB) =0. They do not affect the size or count of a datatype, and do not affect the context of a message created with this datatype. However, they do affect the definition of the extent of a datatype and, therefore, affect the outcome of a replication of this datatype by a datatype constructor. In general, if ``` Typemap = {(type(0), disp(0)), ..., (type(n-1), disp(n-1))} ``` then the lower bound of Typemap is defined to be ``` (min(j) disp(j) if no entry has lb(Typemap) = ( basic type lb (min(j) {disp(j) such that type(j) = lb} otherwise ``` Similarly, the upper bound of Typemap is defined to be ``` (max(j) disp(j) + sizeof(type(j) = lb} if no entry has ub(Typemap) = ( basic type ub (max(j) {disp(j) such that type(j) = ub} otherwise ``` Then ``` extent(Typemap) = ub(Typemap) - lb(Typemap) ``` If type(i) requires alignment to a byte address that is a multiple of k(i), then e is the least nonnegative increment needed to round extent(Typemap) to the next multiple of max(i) k(i). # [ERRORS](#ERRORS) Almost all MPI routines return an error value; C routines as the return result of the function and Fortran routines in the last argument. Before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. If no communication object is associated with the MPI call, then the call is considered attached to MPI\_COMM\_SELF and will call the associated MPI error handler. When MPI\_COMM\_SELF is not initialized (i.e., before MPI\_Init <#mpi-init>/MPI\_Init\_thread <#mpi-init-thread>, after MPI\_Finalize <#mpi-finalize>, or when using the Sessions Model exclusively) the error raises the initial error handler. The initial error handler can be changed by calling MPI\_Comm\_set\_errhandler <#mpi-comm-set-errhandler> on MPI\_COMM\_SELF when using the World model, or the mpi\_initial\_errhandler CLI argument to mpiexec or info key to MPI\_Comm\_spawn <#mpi-comm-spawn>/MPI\_Comm\_spawn\_multiple <#mpi-comm-spawn-multiple>. If no other appropriate error handler has been set, then the MPI\_ERRORS\_RETURN error handler is called for MPI I/O functions and the MPI\_ERRORS\_ABORT error handler is called for all other MPI functions. Open MPI includes three predefined error handlers that can be used: - **MPI\_ERRORS\_ARE\_FATAL** Causes the program to abort all connected MPI processes. - **MPI\_ERRORS\_ABORT** An error handler that can be invoked on a communicator, window, file, or session. When called on a communicator, it acts as if MPI\_Abort <#mpi-abort> was called on that communicator. If called on a window or file, acts as if MPI\_Abort <#mpi-abort> was called on a communicator containing the group of processes in the corresponding window or file. If called on a session, aborts only the local process. - **MPI\_ERRORS\_RETURN** Returns an error code to the application. MPI applications can also implement their own error handlers by calling: - MPI\_Comm\_create\_errhandler <#mpi-comm-create-errhandler> then MPI\_Comm\_set\_errhandler <#mpi-comm-set-errhandler> - MPI\_File\_create\_errhandler <#mpi-file-create-errhandler> then MPI\_File\_set\_errhandler <#mpi-file-set-errhandler> - MPI\_Session\_create\_errhandler <#mpi-session-create-errhandler> then MPI\_Session\_set\_errhandler <#mpi-session-set-errhandler> or at MPI\_Session\_init <#mpi-session-init> - MPI\_Win\_create\_errhandler <#mpi-win-create-errhandler> then MPI\_Win\_set\_errhandler <#mpi-win-set-errhandler> Note that MPI does not guarantee that an MPI program can continue past an error. See the MPI man page <#open-mpi> for a full list of MPI error codes <#open-mpi-errors>. See the Error Handling section of the MPI-3.1 standard for more information. **See also:** • MPI\_Type\_get\_extent <#mpi-type-get-extent> # [Copyright](#Copyright) 2003-2026, The Open MPI Community September 17, 2026 --- Document: MPI_Type_ub(3) from openmpi-cuda-13.4 5.0.11-r0 (Chainguard OS)