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MPI_Type_indexed - Creates an indexed datatype.
#include <mpi.h>
int MPI_Type_indexed(int count, int *array_of_blocklengths,
int *array_of_displacements, MPI_Datatype oldtype,
MPI_Datatype *newtype)
INCLUDE ’mpif.h’
MPI_TYPE_INDEXED(COUNT, ARRAY_OF_BLOCKLENGTHS,
ARRAY_OF_DISPLACEMENTS, OLDTYPE, NEWTYPE, IERROR)
INTEGER COUNT, ARRAY_OF_BLOCKLENGTHS(*)
INTEGER ARRAY_OF_DISPLACEMENTS(*), OLDTYPE, NEWTYPE
INTEGER IERROR
#include <mpi.h>
Datatype Datatype::Create_indexed(int count,
const int array_of_blocklengths[],
const int array_of_displacements[]) const
- count
- Number of blocks -- also number of entries in
array_of_displacements and array_of_blocklengths (nonnegative integer).
- array_of_blocklengths
- Number of elements per block (array of nonnegative
integers).
- array_of_displacements
- Displacement for each block, in multiples
of oldtype extent (array of integer).
- oldtype
- Old datatype (handle).
- newtype
- New datatype (handle).
- IERROR
- Fortran only:
Error status (integer).
The function MPI_Type_indexed allows
replication of an old datatype into a sequence of blocks (each block is
a concatenation of the old datatype), where each block can contain a different
number of copies and have a different displacement. All block displacements
are multiples of the old data type’s extent.
Example: Let oldtype have
type map {(double, 0), (char, 8)}, with extent 16. Let B = (3, 1) and let
D = (4, 0). A call to MPI_Type_indexed(2, B, D, oldtype, newtype) returns
a datatype with type map
{(double, 64), (char, 72), (double, 80), (char, 88),
(double, 96), (char, 104),
(double, 0), (char, 8)}
That is, three copies of the old type starting at displacement 4 x 16 =
64, and one copy starting at displacement 0.
In general, assume that oldtype
has type map
{(type(0), disp(0)), ..., (type(n-1), disp(n-1))},
with extent ex. Let B be the array_of_blocklength argument and D be the
array_of_displacements argument. The newly created datatype has
n x S ^count-1
i = 0 B[i] entries:
{(type(0), disp(0) + D[0]* ex), ...,
(type(n-1), disp(n-1) + D[0]* ex), ...,
(type(0), disp(0) + (D[0] + B[0]-1)* ex), ...,
(type(n-1), disp(n-1) + (D[0]+ B[0]-1)* ex), ...,
(type(0), disp(0) + D[count-1]* ex), ...,
(type(n-1), disp(n-1) + D[count-1]* ex), ...,
(type(0), disp(0) + (D[count-1] + B[count-1] -1)* ex), ...,
(type(n-1), disp(n-1) + (D[count-1] + B[count-1] -1)* ex)}
A call to MPI_Type_vector(count, blocklength, stride, oldtype, newtype)
is equivalent to a call to MPI_Type_indexed(count, B, D, oldtype, newtype)
where
D[j] = j * stride, j = 0,..., count-1
and
B[j] = blocklength, j = 0, .., count-1
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.
MPI_Type_create_hindexed
MPI_Type_hindexed
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