MPI_Type_indexed(3) MPI MPI_Type_indexed(3)NAMEMPI_Type_indexed - Creates an indexed datatype
SYNOPSIS
int MPI_Type_indexed(int count,
MPICH2_CONST int blocklens[],
MPICH2_CONST int 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 inte‐
gers)
indices
- displacement of each block in multiples of old_type (array of
integers)
old_type
- old datatype (handle)
OUTPUT PARAMETER
newtype
- new datatype (handle)
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 com‐
mon 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
call MPI_TYPE_INDEXED(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 com‐
municators), 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 prede‐
fined 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_ERR_COUNT
- Invalid count argument. Count arguments must be non-negative;
a count of zero is often valid.
MPI_ERR_TYPE
- Invalid datatype argument. May be an uncommitted MPI_Datatype
(see MPI_Type_commit ).
MPI_ERR_ARG
- Invalid argument. Some argument is invalid and is not identi‐
fied by a specific error class (e.g., MPI_ERR_RANK ).
MPI_ERR_INTERN
- This error is returned when some part of the MPICH implementa‐
tion is unable to acquire memory.
LOCATION
src/mpi/datatype/type_indexed.c
9/20/2012 MPI_Type_indexed(3)
