MPI_Type_indexed(3) Open MPI MPI_Type_indexed(3)
NAME
MPI_Type_indexed, MPI_Type_create_hindexed - Creates an indexed
datatype.
SYNTAX
C Syntax
#include <mpi.h>
int MPI_Type_indexed(int count, const int array_of_blocklengths[],
const int array_of_displacements[], MPI_Datatype oldtype,
MPI_Datatype *newtype)
int MPI_Type_create_hindexed(int count,
const int array_of_blocklengths[],
const MPI_Aint array_of_displacements[], MPI_Datatype oldtype,
MPI_Datatype *newtype)
Fortran Syntax
USE MPI
! or the older form: 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
MPI_TYPE_CREATE_HINDEXED(COUNT, ARRAY_OF_BLOCKLENGTHS,
ARRAY_OF_DISPLACEMENTS, OLDTYPE, NEWTYPE, IERROR)
INTEGER COUNT, ARRAY_OF_BLOCKLENGTHS(*)
INTEGER OLDTYPE, NEWTYPE
INTEGER(KIND=MPI_ADDRESS_KIND) ARRAY_OF_DISPLACEMENTS(*)
INTEGER IERROR
Fortran 2008 Syntax
USE mpi_f08
MPI_Type_indexed(count, array_of_blocklengths, array_of_displacements,
oldtype, newtype, ierror)
INTEGER, INTENT(IN) :: count, array_of_blocklengths(count),
array_of_displacements(count)
TYPE(MPI_Datatype), INTENT(IN) :: oldtype
TYPE(MPI_Datatype), INTENT(OUT) :: newtype
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
MPI_Type_create_hindexed(count, array_of_blocklengths,
array_of_displacements, oldtype, newtype, ierror)
INTEGER, INTENT(IN) :: count, array_of_blocklengths(count)
INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) ::
array_of_displacements(count)
TYPE(MPI_Datatype), INTENT(IN) :: oldtype
TYPE(MPI_Datatype), INTENT(OUT) :: newtype
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
C++ Syntax
#include <mpi.h>
Datatype Datatype::Create_indexed(int count,
const int array_of_blocklengths[],
const int array_of_displacements[]) const
Datatype Datatype::Create_hindexed(int count,
const int array_of_blocklengths[],
const MPI::Aint array_of_displacements[]) const
INPUT PARAMETERS
count Number of blocks -- also number of entries in array_of_dis-
placements 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
for MPI_Type_indexed and bytes for MPI_Type_create_hindexed
(array of integer for MPI_TYPE_INDEXED, array of MPI_Aint for
MPI_TYPE_CREATE_HINDEXED).
oldtype Old datatype (handle).
OUTPUT PARAMETERS
newtype New datatype (handle).
IERROR Fortran only: Error status (integer).
DESCRIPTION
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 multi-
ples of the old data type's extent.
Example: Let oldtype have type map {(double, 0), (char, 8)}, with ex-
tent 16. Let B = (3, 1) and let D = (4, 0). A call to MPI_Type_in-
dexed(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, new-
type) where
D[j] = j * stride, j = 0,..., count-1
and
B[j] = blocklength, j = 0, .., count-1
The function MPI_Type_create_hindexed is identical to MPI_Type_indexed,
except that block displacements in array_of_displacements are specified
in bytes, rather than in multiples of the oldtype extent.
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++ func-
tions 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 ALSO
MPI_Type_hindexed
4.1.2 Nov 24, 2021 MPI_Type_indexed(3)
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