NAME

       MPI_Gatherv_init -  Create a persistent request for gatherv.

SYNOPSIS

       int MPI_Gatherv_init(const void *sendbuf, int sendcount, MPI_Datatype sendtype,
       void *recvbuf, const int recvcounts[], const int displs[],
       MPI_Datatype recvtype, int root, MPI_Comm comm,
       MPI_Info info, MPI_Request *request)

       int MPI_Gatherv_init_c(const void *sendbuf, MPI_Count sendcount,
       MPI_Datatype sendtype, void *recvbuf,
       const MPI_Count recvcounts[], const MPI_Aint displs[],
       MPI_Datatype recvtype, int root, MPI_Comm comm,
       MPI_Info info, MPI_Request *request)

INPUT PARAMETERS

       sendbuf
              - starting address of send buffer (choice)
       sendcount
              - number of elements in send buffer (non-negative integer)
       sendtype
              - data type of send buffer elements (handle)
       recvcounts
              -  non-negative  integer  array  (of  length  group  size) containing the number of
              elements that are received from each process (non-negative integer)
       displs - integer array (of length group size). Entry i specifies the displacement relative
              to recvbuf at which to place the incoming data from process i (integer)
       recvtype
              - data type of recv buffer elements (handle)
       root   - rank of receiving process (integer)
       comm   - communicator (handle)
       info   - info argument (handle)

OUTPUT PARAMETERS

       recvbuf
              - address of receive buffer (choice)
       request
              - communication request (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.

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
       communicators),  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  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 whenever possible.

       MPI_SUCCESS
              - No error; MPI routine completed successfully.
       MPI_ERR_ARG
              -  Invalid  argument.  Some argument is invalid and is not identified by a specific
              error class (e.g., MPI_ERR_RANK ).
       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  communicator  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_INFO
              - Invalid Info
       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.

                                             2/9/2024                         MPI_Gatherv_init(3)