MPI_File_iread(3)

NAME
     MPI_File_iread - Performs a nonblocking read using an individual file
     pointer

SYNOPSIS
     C:

          #include "mpi.h"

          int MPI_File_iread (MPI_File fh, void *buf,
          int count, MPI_Datatype datatype, MPIO_Request *request)


     Fortran:

          INCLUDE "mpif.h" (or USE MPI)

          <type> BUF(*)
          INTEGER fh, count, datatype, request,
          ierror

          CALL MPI_FILE_IREAD(fh, buf, count, datatype,
          request, ierror)


DESCRIPTION
     MPI_File_iread is a nonblocking version of the MPI_FILE_READ interface.

     MPI_File_iread accepts the following arguments:

     fh        Specifies the file handle (handle)

     count     Specifies the number of elements in the buffer (nonnegative
               integer)

     datatype  Specifies the datatype of each buffer element (handle)

     buf       Returns the initial address of the buffer (choice)

     request   Returns the request object (handle)

     ierror    Specifies the return code value for successful completion,
               which is in MPI_SUCCESS.  MPI_SUCCESS is defined in the mpif.h
               file.

   Limitations
     In Fortran and C, the routines MPIO_Wait and MPIO_Test must be used
     instead of MPI_Wait and MPI_Test, respectively.  This is a nonstandard
     restriction and might change in an upcoming release.
   Notes for Fortran
     All MPI objects (for example, MPI_Datatype, MPI_Comm, MPI_File) are of
     type INTEGER.

EXAMPLES
     The following Fortran code fragment illustrates file pointer update
     semantics:

     !   Read the first twenty real words in a file into two local
     !   buffers.  Note that when the first MPI_FILE_IREAD returns,
     !   the file pointer has been updated to point to the
     !   eleventh real word in the file.

     integer   bufsize, req1, req2
           integer, dimension(MPI_STATUS_SIZE) :: status1, status2
           parameter (bufsize=10)
           real      buf1(bufsize), buf2(bufsize)

     call MPI_FILE_OPEN( MPI_COMM_WORLD, 'myoldfile', &
                               MPI_MODE_RDONLY, MPI_INFO_NULL, myfh, ierr )
           call MPI_FILE_SET_VIEW( myfh, 0, MPI_REAL, MPI_REAL, 'native', &
                              MPI_INFO_NULL, ierr )
           call MPI_FILE_IREAD( myfh, buf1, bufsize, MPI_REAL, &
                                req1, ierr )
           call MPI_FILE_IREAD( myfh, buf2, bufsize, MPI_REAL, &
                                req2, ierr )

     call MPIO_WAIT( req1, status1, ierr )
     call MPIO_WAIT( req2, status2, ierr )

     call MPI_FILE_CLOSE( myfh, ierr )


SEE ALSO
     MPI_File_close(3), MPI_File_open(3), MPI_File_read(3),
     MPI_File_set_view(3), MPI_IO(3)