MPI_TYPE_CREATE_F90_REAL(3)			     Open MPI			       MPI_TYPE_CREATE_F90_REAL(3)

	  MPI_Type_create_f90_real - Returns a bounded MPI real datatype

SYNTAX
   C Syntax
	  #include <mpi.h>

	  int MPI_Type_create_f90_real(int p, int r, MPI_Datatype *newtype)

   Fortran Syntax
	  USE MPI
	  ! or the older form: INCLUDE 'mpif.h'
	  MPI_TYPE_CREATE_F90_REAL (P, R, NEWTYPE, IERROR)
	       INTEGER P, R, NEWTYPE, IERROR

   Fortran 2008 Syntax
	  USE mpi_f08
	  MPI_Type_create_f90_real(p, r, newtype, ierror)
	       INTEGER, INTENT(IN) :: p, r
	       TYPE(MPI_Datatype), INTENT(OUT) :: newtype
	       INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS
       • p: Precision, in decimal digits (integer).

       • r: Decimal exponent range (integer).

OUTPUT PARAMETERS
       • newtype: New data type (handle).

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

DESCRIPTION
       This  function  provides	 a  way	 to  declare  KIND-parameterized  REAL	MPI  datatypes.	 The arguments are
       interpreted in a similar fashion to the F90 function SELECTED_REAL_KIND. The parameters p  and  r  must	be
       scalar  integers.  The  argument p represents the required level of numerical precision, in decimal digits.
       The r parameter indicates the range of exponents desired: the returned datatype	will  have  at	least  one
       exponent between +r and -r (inclusive).

       Either p or r, but not both, may be omitted from calls to SELECTED_REAL_KIND. Similarly, either argument to
       MPI_Type_create_f90_real may be set to MPI_UNDEFINED.

NOTES
       It is erroneous to supply values for p and r not supported by the compiler.

       The Fortran function SELECTED_REAL_KIND maps a large number of (p,r) pairs 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  (p,r)  arguments	to
       SELECTED_REAL_KIND.  However,  to  help	facilitate  interoperability  in  a   heterogeneous   environment,
       equivalency is more strictly defined for datatypes returned by MPI_Type_create_f90_real. Two MPI datatypes,
       each generated by this function, will match if and only if they have identical values for both p and r.

       The  interaction	 between  the datatypes returned by this function and the external32 data representation -
       used  by	 MPI_Pack_external  <#mpi-pack-external>,  MPI_Unpack_external	<#mpi-unpack-external>	and   many
       MPI_File functions - is subtle. The external32 representation of returned datatypes is as follows.

	  if (p > 33) and/or (r > 4931):
		  external32 size = n/a (undefined)
	  else if (p > 15) and/or (r > 307):
		  external32 size = 16
	  else if (p > 6) and/or (r > 37):
		  external32 size = 8
	  else:
		  external32 size = 4

       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_REAL_KIND
       (i.e., p and/or r are unknown), the only way to obtain a matching MPI datatype  is  to  use  the	 functions
       MPI_Sizeof <#mpi-sizeof> and MPI_Type_match_size <#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>/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_Pack_external <#mpi-pack-external>

	  • MPI_Sizeof <#mpi-sizeof>

	  • MPI_Type_match_size <#mpi-type-match-size>

	  • MPI_Unpack_external <#mpi-unpack-external>

	  • SELECTED_REAL_KIND

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026			       MPI_TYPE_CREATE_F90_REAL(3)
