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MPI_Type_struct(3)		      MPI		    MPI_Type_struct(3)

NAME
       MPI_Type_struct -  Creates a struct datatype

SYNOPSIS
       int MPI_Type_struct(int count,
			  MPICH2_CONST int blocklens[],
			  MPICH2_CONST MPI_Aint	indices[],
			  MPICH2_CONST MPI_Datatype old_types[],
			  MPI_Datatype *newtype)

INPUT PARAMETERS
       count  -	number of blocks (integer) -- also number of entries in	arrays
	      array_of_types  ,	 array_of_displacements	  and  array_of_block-
	      lengths
       blocklens
	      -	number of elements in each block (array)
       indices
	      -	byte displacement of each block	(array)
       old_types
	      -	 type  of elements in each block (array	of handles to datatype
	      objects)

OUTPUT PARAMETER
       newtype
	      -	new datatype (handle)

DEPRECATED FUNCTION
       The MPI-2 standard deprecated a number of routines because  MPI-2  pro-
       vides  better  versions.	  This routine is one of those that was	depre-
       cated.  The routine may continue	to be used, but	new  code  should  use
       the   replacement   routine.   The  replacement	for  this  routine  is
       MPI_Type_create_struct

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

       The  MPI	 standard  originally  made vague statements about padding and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)	; for example,
       sizeof(foo) == 2*sizeof(int) .  The initial version of the MPI standard
       defined	the  extent  of	 a datatype as including an epsilon that 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, there
       was much	discussion by the MPI Forum about what was the	correct	 value
       of  epsilon,  and  one  suggestion was to define	epsilon	as zero.  This
       would have been the best	thing to do in MPI 1.0,	particularly since the
       MPI_UB  type  allows  the  user to easily set the end of	the structure.
       Unfortunately, this change did not make it  into	 the  final  document.
       Currently,  this	 routine does not add any padding, since the amount of
       padding needed is determined by the compiler that the user is using  to
       build  their  code, not the compiler used to construct the MPI library.
       A later version of MPICH	may provide for	some natural choices  of  pad-
       ding  (e.g.,  multiple  of  the	size of	the largest basic member), but
       users are advised to never depend on this, even with vendor MPI	imple-
       mentations.   Instead,  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 );

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.

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_er-
       rhandler	(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	 when-
       ever 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 implementa-
	      tion is unable to	acquire	memory.

LOCATION
       src/mpi/datatype/type_struct.c

				   9/20/2012		    MPI_Type_struct(3)

NAME | SYNOPSIS | INPUT PARAMETERS | OUTPUT PARAMETER | DEPRECATED FUNCTION | NOTES | THREAD AND INTERRUPT SAFETY | NOTES FOR FORTRAN | ERRORS | LOCATION

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