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       MPI_Allgatherv -  Gathers data from all tasks and deliver it to all


       #include <mpi.h>
       int MPI_Allgatherv(void *sbuf, int scount, MPI_Datatype sdtype,
                         void * rbuf, int *rcounts, int *disps,
                         MPI_Datatype rdtype, MPI_Comm comm)


       sbuf   - starting address of send buffer (choice)
       scount - number of elements in send buffer (integer)
       sdtype - data type of send buffer elements (handle)
              -  integer array (of length group size) containing the number of
              elements that are received from each process
       disps  - integer array (of length group size). Entry  i  specifies  the
              displacement  (relative  to  recvbuf  )  at  which  to place the
              incoming data from process i

       rdtype - data type of receive buffer elements (handle)
       comm   - communicator (handle)


       rbuf   - address of receive buffer (choice)


       The MPI standard (1.0 and 1.1) says that

       "The jth block of data sent from  each  proess  is  received  by  every
       process and placed in the jth block of the buffer recvbuf."

       This is misleading; a better description is

       "The  block  of  data  sent  from  the jth process is received by every
       process and placed in the jth block of the buffer recvbuf."

       This text was suggested by Rajeev Thakur.


       LAM/MPI does not yet support invoking this function on  a  communicator
       that contains ranks that are non-local IMPI procs.


       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


       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.
              -  Invalid  communicator.   A  common  error  is  to  use a null
              communicator in a call (not even allowed in MPI_Comm_rank ).
              - A collective implementation was not able to be located at run-
              time for this communicator.
              -  A  communicator  that  contains some non-local IMPI procs was
              used for some function which has not yet had the IMPI extensions
              implemented   yet.    For  example,  most  collectives  on  IMPI
              communicators have not been implemented yet.
              - Invalid buffer pointer.  Usually a null buffer  where  one  is
              not valid.
              - Invalid count argument.  Count arguments must be non-negative;
              a count of zero is often valid.
              - Invalid datatype argument.  May be an uncommitted MPI_Datatype
              (see MPI_Type_commit ).


       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).


       The LAM Team would like the thank the MPICH Team for the handy  program
       to        generate        man        pages        ("doctext"       from    ),    the     initial
       formatting, and some initial text for most of the MPI-1 man pages.