Open MPI logo

MPI_Type_struct(3) man page (version 1.3.4)

  |   Home   |   Support   |   FAQ   |  

« Return to documentation listing



NAME

       MPI_Type_struct  - Creates a struct data type -- use of this routine is
       deprecated.

SYNTAX


C Syntax

       #include <mpi.h>
       int MPI_Type_struct(int count, int *array_of_blocklengths,
            MPI_Aint *array_of_displacements, MPI_Datatype *array_of_types,
            MPI_Datatype *newtype)

Fortran Syntax

       INCLUDE 'mpif.h'
       MPI_TYPE_STRUCT(COUNT, ARRAY_OF_BLOCKLENGTHS,
                 ARRAY_OF_DISPLACEMENTS, ARRAY_OF_TYPES,
                 NEWTYPE, IERROR)
            INTEGER   COUNT, ARRAY_OF_BLOCKLENGTHS(*)
            INTEGER   ARRAY_OF_DISPLACEMENTS(*)
            INTEGER   ARRAY_OF_TYPES(*), NEWTYPE, IERROR

INPUT PARAMETERS

       count     Number of blocks (integer)  also number of entries in  arrays
                 array_of_types,   array_of_displacements, and array_of_block-
                 lengths.

       array_of_blocklengths
                 Number of elements in each block (array).

       array_of_displacements
                 Byte displacement of each block (array).

       array_of_types
                 Type of elements in each block (array of handles to  datatype
                 objects).

OUTPUT PARAMETERS

       newtype   New datatype (handle).

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       Note  that  use  of  this  routine  is  deprecated  as  of  MPI-2.  Use
       MPI_Type_create_struct instead.

       This deprecated routine is not available in C++.

       MPI_Type_struct is the most general type constructor. It further gener-
       alizes  MPI_Type_hindexed  in  that  it allows each block to consist of
       replications of different datatypes.

       Example: Let type1 have type map
           (char, 26), (char, 27), (char, 28)}

       That is, two copies of MPI_FLOAT starting at 0, followed by one copy of
       type1 starting at 16, followed by three copies of MPI_CHAR, starting at
       26. (We assume that a float occupies 4 bytes.)

       For more information, see section 3.12.1 of the MPI-1.1 Standard.

NOTES

       If an upperbound is set explicitly by using the  MPI  datatype  MPI_UB,
       the corresponding index must be positive.

       The  MPI-1  Standard originally made vague statements about padding and
       alignment; this was intended to allow the simple definition  of  struc-
       tures that could be sent with a count greater than one. For example,
           struct {int a; char b;} foo;
       may have
           sizeof(foo) = sizeof(int) + sizeof(char);
       defining  the extent of a datatype as including an epsilon, which would
       have allowed an implementation to make the extent an MPI  datatype  for
       this structure equal to 2*sizeof(int). However, since different systems
       might define different paddings, a clarification to the  standard  made
       epsilon zero. Thus, if you define a structure datatype and wish to send
       or receive multiple items, you  should  explicitly  include  an  MPI_UB
       entry  as the last member of the structure.  For example, the following
       code can be used for the structure foo:

           blen[0] = 1; indices[0] = 0; oldtypes[0] = MPI_INT;
           blen[1] = 1; indices[1] = &foo.b - &foo; oldtypes[1] = MPI_CHAR;
           blen[2] = 1; indices[2] = sizeof(foo); oldtypes[2] = MPI_UB;
           MPI_Type_struct( 3, blen, indices, oldtypes, &newtype );

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_create_struct
       MPI_Type_create_hindexed

1.3.4                            Nov 11, 2009               MPI_Type_struct(3)

« Return to documentation listing