bionic (3) MPI_File_read_at_all_begin.openmpi.3.gz

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)

       USE MPI
       ! or the older form: 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. FORTRAN
       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.