MPI_Type_indexed(3)                Open MPI                MPI_Type_indexed(3)



NAME
       MPI_Type_indexed - Creates an indexed datatype.


SYNTAX
C Syntax
       #include <mpi.h>
       int MPI_Type_indexed(int count, int *array_of_blocklengths,
            int *array_of_displacements, MPI_Datatype oldtype,
            MPI_Datatype *newtype)


Fortran Syntax
       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


C++ Syntax
       #include <mpi.h>
       Datatype Datatype::Create_indexed(int count,
            const int array_of_blocklengths[],
            const int array_of_displacements[]) const


INPUT PARAMETERS
       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).


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
       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


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 ALSO
       MPI_Type_create_hindexed
       MPI_Type_hindexed




1.4.1                            Jan 14, 2010              MPI_Type_indexed(3)
