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MPI_Type_create_f90_integer - Returns a bounded MPI integer datatype
#include <mpi.h>
int MPI_Type_create_f90_integer(int r, MPI_Datatype *newtype)
USE MPI
! or the older form: INCLUDE ’mpif.h’
MPI_TYPE_CREATE_F90_INTEGER (R, NEWTYPE, IERROR)
INTEGER R, NEWTYPE, IERROR
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
- r
- Precision, in decimal digits (integer).
- newtype
- New data type (handle).
- IERROR
- Fortran only: Error status (integer).
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.
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.
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.
MPI_Pack_external
MPI_Sizeof
MPI_Type_match_size
MPI_Unpack_external
SELECTED_INT_KIND
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