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MPI_File_read_at_all_begin(3OpenMPI)                                    MPI_File_read_at_all_begin(3OpenMPI)



NAME
       MPI_File_read_at_all_begin  - Reads a file at explicitly specified offsets; beginning part of a split
       collective routine (nonblocking).


SYNTAX
       C Syntax
           #include <mpi.h>
           int MPI_File_read_at_all_begin(MPI_File fh, MPI_Offset
            offset, void *buf, int count, MPI_Datatype
            datatype)

       Fortran Syntax (see FORTRAN 77 NOTES)
           INCLUDE 'mpif.h'
           MPI_FILE_READ_AT_ALL_BEGIN(FH, OFFSET, BUF,
            COUNT, DATATYPE, IERROR)
                 <type> BUF(*)
                 INTEGER   FH, COUNT, DATATYPE, IERROR
                 INTEGER(KIND=MPI_OFFSET_KIND) OFFSET


C++ Syntax
       #include <mpi.h>
       void MPI::File::Read_at_all_begin(MPI::Offset offset, void* buf,
            int count, const MPI::Datatype& datatype)


INPUT PARAMETERS
       fh        File handle (handle).

       offset    File offset (integer).

       count     Number of elements in buffer (integer).

       datatype  Data type of each buffer element.


OUTPUT PARAMETERS
       buf       Initial address of buffer (choice).

       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       MPI_File_read_at_all_begin is the beginning part of a split collective routine that attempts to  read
       from  the  file associated with fh (at the offset position) a total number of count data items having
       datatype type into the user's buffer buf.  The offset is in etype units relative to the current view.
       That  is,  holes are not counted when locating an offset. The data is taken out of those parts of the
       file specified by the current view.


FORTRAN 77 NOTES
       The MPI standard prescribes portable Fortran syntax for the OFFSET argument only for Fortran 90. FOR-TRAN FORTRAN
       TRAN 77 users may use the non-portable syntax

            INTEGER*MPI_OFFSET_KIND OFFSET

       where MPI_OFFSET_KIND is a constant defined in mpif.h and gives the length of the declared integer in
       bytes.


NOTES
       All the nonblocking collective routines for data access are "split"  into  two  routines,  each  with
       _begin  or  _end  as  a  suffix.  These  split  collective routines are subject to the semantic rules
       described in Section 9.4.5 of the MPI-2 standard.


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++ functions 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. For MPI I/O function
       errors, the default error handler is set to MPI_ERRORS_RETURN. The error handler may be changed  with
       MPI_File_set_errhandler;  the  predefined  error handler MPI_ERRORS_ARE_FATAL may be used to make I/O
       errors fatal. Note that MPI does not guarantee that an MPI program can continue past an error.




Open MPI 1.2                                   September 2006           MPI_File_read_at_all_begin(3OpenMPI)