MPI_Type_hindexed

Creates an indexed datatype with offsets in bytes

Synopsis

int MPI_Type_hindexed(int count,
                     int blocklens[],
                     MPI_Aint indices[],
                     MPI_Datatype old_type,
                     MPI_Datatype *newtype)

Input Parameters

count

number of blocks -- also number of entries in indices and blocklens

blocklens

number of elements in each block (array of nonnegative integers)

indices

byte displacement of each block (array of MPI_Aint)

old_type

old datatype (handle)

Output Parameter

newtype

new datatype (handle)

Deprecated Function

The MPI-2 standard deprecated a number of routines because MPI-2 provides better versions. This routine is one of those that was deprecated. The routine may continue to be used, but new code should use the replacement routine. This routine is replaced by MPI_Type_create_hindexed.

Thread and Interrupt Safety

This routine is thread-safe. This means that this routine may be safely used by multiple threads without the need for any user-provided thread locks. However, the routine is not interrupt safe. Typically, this is due to the use of memory allocation routines such as malloc or other non-MPICH runtime routines that are themselves not interrupt-safe.

Notes for Fortran

All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) have an additional argument ierr at the end of the argument list. ierr is an integer and has the same meaning as the return value of the routine in C. In Fortran, MPI routines are subroutines, and are invoked with the call statement.

All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran.

The indices are displacements, and are based on a zero origin. A common error is to do something like to following

    integer a(100)
    integer blens(10), indices(10)
    do i=1,10
         blens(i)   = 1
10       indices(i) = (1 + (i-1)*10) * sizeofint
    call MPI_TYPE_HINDEXED(10,blens,indices,MPI_INTEGER,newtype,ierr)
    call MPI_TYPE_COMMIT(newtype,ierr)
    call MPI_SEND(a,1,newtype,...)

expecting this to send a(1),a(11),... because the indices have values 1,11,.... Because these are displacements from the beginning of a, it actually sends a(1+1),a(1+11),....

If you wish to consider the displacements as indices into a Fortran array, consider declaring the Fortran array with a zero origin

    integer a(0:99)

Errors

All MPI routines (except MPI_Wtime and MPI_Wtick) return an error value; C routines as the value of the function and Fortran routines in the last argument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error handler may be changed with MPI_Comm_set_errhandler (for communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for RMA windows). The MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated. The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarentee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible.

MPI_SUCCESS

No error; MPI routine completed successfully.

MPI_ERR_TYPE

Invalid datatype argument. May be an uncommitted MPI_Datatype (see MPI_Type_commit).

MPI_ERR_COUNT

Invalid count argument. Count arguments must be non-negative; a count of zero is often valid.

MPI_ERR_INTERN

This error is returned when some part of the MPICH implementation is unable to acquire memory.

MPI_ERR_ARG

Invalid argument. Some argument is invalid and is not identified by a specific error class (e.g., MPI_ERR_RANK).

Location:type_hindexed.c