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MPI_Alltoallv(3)		      MPI		      MPI_Alltoallv(3)

NAME
       MPI_Alltoallv -	Sends data from	all to all processes; each process may
       send a different	amount of data and provide displacements for the input
       and output data.

SYNOPSIS
       int MPI_Alltoallv(const void *sendbuf, const int	sendcounts[],
       const int sdispls[], MPI_Datatype sendtype, void	*recvbuf,
       const int recvcounts[], const int rdispls[],
       MPI_Datatype recvtype, MPI_Comm comm)

       int MPI_Alltoallv_c(const void *sendbuf,	const MPI_Count	sendcounts[],
       const MPI_Aint sdispls[], MPI_Datatype sendtype,
       void *recvbuf, const MPI_Count recvcounts[],
       const MPI_Aint rdispls[], MPI_Datatype recvtype,
       MPI_Comm	comm)

INPUT PARAMETERS
       sendbuf
	      -	starting address of send buffer	(choice)
       sendcounts
	      -	 non-negative  integer array (of length	group size) specifying
	      the number of elements to	send to	each rank (non-negative	 inte-
	      ger)
       sdispls
	      -	 integer  array	 (of length group size). Entry j specifies the
	      displacement (relative to	sendbuf) from which to take the	outgo-
	      ing data destined	for process j (integer)
       sendtype
	      -	data type of send buffer elements (handle)
       recvcounts
	      -	non-negative integer array (of length group  size)  specifying
	      the number of elements that can be received from each rank (non-
	      negative integer)
       rdispls
	      -	 integer  array	 (of length group size). Entry i specifies the
	      displacement (relative to	recvbuf) at which to place the	incom-
	      ing data from process i (integer)
       recvtype
	      -	data type of receive buffer elements (handle)
       comm   -	communicator (handle)

OUTPUT PARAMETERS
       recvbuf
	      -	address	of receive buffer (choice)

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 guarantee 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_BUFFER
	      -	 Invalid  buffer  pointer.  Usually a null buffer where	one is
	      not valid.
       MPI_ERR_COMM
	      -	Invalid	communicator.  A common	error is to use	a null	commu-
	      nicator in a call	(not even allowed in MPI_Comm_rank ).
       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.  Additionally, this error can occur
	      if an uncommitted	MPI_Datatype (see MPI_Type_commit ) is used in
	      a	communication call.
       MPI_ERR_OTHER
	      -	 Other	error;	use  MPI_Error_string  to get more information
	      about this error code.

				   2/3/2025		      MPI_Alltoallv(3)

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