SYNTAX

   C Syntax
          #include <mpi.h>

          int MPI_Type_create_f90_integer(int r, MPI_Datatype *newtype)

   Fortran Syntax
          USE MPI
          ! or the older form: INCLUDE 'mpif.h'
          MPI_TYPE_CREATE_F90_INTEGER (R, NEWTYPE, IERROR)
               INTEGER R, NEWTYPE, IERROR

   Fortran 2008 Syntax
          USE mpi_f08
          MPI_Type_create_f90_integer(r, newtype, ierror)
               INTEGER, INTENT(IN) :: r
               TYPE(MPI_Datatype), INTENT(OUT) :: newtype
               INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETER

       • r: Precision, in decimal digits (integer).

OUTPUT PARAMETERS

       • newtype: New data type (handle).

       • ierror: Fortran only: Error status (integer).

DESCRIPTION

       This  function  provides  a  way  to  declare  KIND-parameterized  INTEGER MPI datatypes. The argument is
       interpreted in a similar fashion to the F90 function SELECTED_INT_KIND: r must be a scalar  integer,  and
       represents the desired level of numerical precision, in decimal digits.

NOTES

       It is erroneous to supply a value for r not supported by the compiler.

       The  Fortran  function SELECTED_INT_KIND maps a large number of r values to a much smaller number of KIND
       parameters supported by the compiler.  KIND parameters are not specified by  the  language  and  are  not
       portable.  From the point of view of the language, variables of the same base type and KIND parameter are
       equivalent,  even  if their KIND parameters were generated by different r arguments to SELECTED_INT_KIND.
       However, to help facilitate interoperability in a heterogeneous environment, equivalency is more strictly
       defined for datatypes returned by MPI_Type_create_f90_integer. Two MPI datatypes, each generated by  this
       function, will match if and only if they have identical values for r.

       The  interaction between the datatypes returned by this function and the external32 data representation -
       used by MPI_Pack_external, MPI_Unpack_external and many MPI_File functions - is  subtle.  The  external32
       representation of returned datatypes is as follows.

          if (r > 38):
                  external32 size = n/a (undefined)
          else if (r > 18):
                  external32 size = 16
          else if (r > 9):
                  external32 size = 8
          else if (r > 4):
                  external32 size = 4
          else if (r > 2):
                  external32 size = 2
          else:
                  external32 size = 1

       If the external32 representation of a datatype is undefined, so are the results of using that datatype in
       operations  that  require  the  external32 format. Care should be taken not to use incompatible datatypes
       indirectly, e.g., as part of another datatype or through a duplicated datatype, in these functions.

       If a variable is declared specifying a nondefault KIND value that was not obtained with SELECTED_INT_KIND
       (i.e., r is unknown), the only way to obtain a matching MPI datatype is to use the  functions  MPI_Sizeof
       and MPI_Type_match_size.

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_thread,  after
       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 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_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 was called on that communicator. If called on a
         window or file, acts as if 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 then MPI_Comm_set_errhandler

       • MPI_File_create_errhandler then MPI_File_set_errhandler

       • MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init

       • MPI_Win_create_errhandler then MPI_Win_set_errhandler

       Note that MPI does not guarantee that an MPI program can continue past an error.

       See the MPI man page for a full list of MPI error codes.

       See the Error Handling section of the MPI-3.1 standard for more information.

       SEE ALSO:

          • MPI_Pack_external

          • MPI_Sizeof

          • MPI_Type_match_size

          • MPI_Unpack_external

          • SELECTED_INT_KIND

COPYRIGHT

       2003-2025, The Open MPI Community

                                                  Feb 17, 2025                    MPI_TYPE_CREATE_F90_INTEGER(3)