NAME
MPI_Type_indexed - Creates an indexed datatype
SYNOPSIS
#include <mpi.h>
int MPI_Type_indexed(int count, int *lengths, int *disps,
MPI_Datatype oldtype, MPI_Datatype *newtype)
INPUT PARAMETERS
count - number of blocks -- also number of entries in indices and
blocklens
lengths
- number of elements in each block (array of nonnegative
integers)
disps - displacement of each block in multiples of old_type (array of
integers)
oldtype
- old datatype (handle)
OUTPUT PARAMETER
newtype
- new datatype (handle)
NOTES
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
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,... (and so on). Because these are disps 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)
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.
ERRORS
If an error occurs in an MPI function, the current MPI error handler is
called to handle it. By default, this error handler aborts the MPI
job. The error handler may be changed with MPI_Errhandler_set ; the
predefined error handler MPI_ERRORS_RETURN may be used to cause error
values to be returned (in C and Fortran; this error handler is less
useful in with the C++ MPI bindings. The predefined error handler
MPI::ERRORS_THROW_EXCEPTIONS should be used in C++ if the error value
needs to be recovered). Note that MPI does not guarantee that an MPI
program can continue past an error.
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. The C++ bindings for MPI do not return error
values; instead, error values are communicated by throwing exceptions
of type MPI::Exception (but not by default). Exceptions are only
thrown if the error value is not MPI::SUCCESS .
Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI
functions will return upon an error, there will be no way to recover
what the actual error value was.
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_COUNT
- Invalid count argument. Count arguments must be non-negative;
a count of zero is often valid.
MPI_ERR_ARG
- Invalid argument. Some argument is invalid and is not
identified by a specific error class. This is typically a NULL
pointer or other such error.
MPI_ERR_OTHER
- This error is returned when some part of the LAM/MPI
implementation is unable to acquire memory.
MORE INFORMATION
For more information, please see the official MPI Forum web site, which
contains the text of both the MPI-1 and MPI-2 standards. These
documents contain detailed information about each MPI function (most of
which is not duplicated in these man pages).
http://www.mpi-forum.org/
ACKNOWLEDGEMENTS
The LAM Team would like the thank the MPICH Team for the handy program
to generate man pages ("doctext" from
ftp://ftp.mcs.anl.gov/pub/sowing/sowing.tar.gz ), the initial
formatting, and some initial text for most of the MPI-1 man pages.
LOCATION
tindex.c