MPI_Type_create_f90_real(3)        Open MPI        MPI_Type_create_f90_real(3)



NAME
       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
       INCLUDE 'mpif.h'
       MPI_TYPE_CREATE_F90_REAL (P, R, NEWTYPE, IERROR)
            INTEGER   P, R, NEWTYPE, IERROR


C++ Syntax
       #include <mpi.h>
       static MPI::Datatype MPI::Datatype::Create_f90_real(int p, int r)


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_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 and MPI_Type_match_size.


ERRORS
       Almost all MPI routines return an error value; C routines as the value
       of the function and Fortran routines in the last argument. C++
       functions do not return errors. If the default error handler is set to
       MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
       will be used to throw an MPI:Exception object.

       Before the error value is returned, the current MPI error handler is
       called. By default, this error handler aborts the MPI job, except for
       I/O function errors. The error handler may be changed with
       MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN
       may be used to cause error values to be returned. 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 ALSO
       MPI_Pack_external
       MPI_Sizeof
       MPI_Type_match_size
       MPI_Unpack_external
       SELECTED_REAL_KIND




1.4.1                            Jan 14, 2010      MPI_Type_create_f90_real(3)
