Provided by: openmpi-doc_1.4.3-2.1ubuntu3_all bug

NAME

       MPI_Type_create_f90_integer - Returns a bounded MPI integer datatype

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Type_create_f90_integer(int r, MPI_Datatype *newtype)

Fortran Syntax

       INCLUDE 'mpif.h'
       MPI_TYPE_CREATE_F90_INTEGER (R, NEWTYPE, IERROR)
            INTEGER   R, NEWTYPE, IERROR

C++ Syntax

       #include <mpi.h>
       static MPI::Datatype MPI::Datatype::Create_f90_integer(int r)

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 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_INT_KIND