C Syntax

       2003-2025, The Open MPI Community

                                                  Jun 07, 2025                              MPI_FILE_READ_ALL(3)

MPI_File_read_all is a collective routine that attempts to read from the file associated with fh (at  the
       current  individual  file  pointer  position maintained by the system) a total number of count data items
       having datatype type into the user’s buffer buf. The data is  taken  out  of  those  parts  of  the  file
       specified  by  the current view.  MPI_File_read_all stores the number of data-type elements actually read
       in status. All other fields of status are undefined.

       It is erroneous to call this function if MPI_MODE_SEQUENTIAL mode was specified when the file was opened.

       Almost all MPI routines return an error value; C routines as  the  return  result  of  the  function  and
       Fortran routines in the last argument.

       Before  the  error  value  is  returned,  the current MPI error handler associated with the communication
       object (e.g., communicator, window, file) is called.  If no communication object is associated  with  the
       MPI  call,  then  the call is considered attached to MPI_COMM_SELF and will call the associated MPI error
       handler.  When  MPI_COMM_SELF  is  not  initialized   (i.e.,   before   MPI_Init/MPI_Init_thread,   after
       MPI_Finalize,  or  when using the Sessions Model exclusively) the error raises the initial error handler.
       The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF  when  using
       the  World  model,  or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_Comm_spawn/‐
       MPI_Comm_spawn_multiple.  If no other appropriate error handler has been set, then the  MPI_ERRORS_RETURN
       error  handler  is  called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all
       other MPI functions.

       Open MPI includes three predefined error handlers that can be used:

       • MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.

       • MPI_ERRORS_ABORT An error handler that can be invoked on a communicator, window, file, or session. When
         called on a communicator, it acts as if MPI_Abort was called on  that  communicator.  If  called  on  a
         window  or file, acts as if MPI_Abort was called on a communicator containing the group of processes in
         the corresponding window or file. If called on a session, aborts only the local process.

       • MPI_ERRORS_RETURN Returns an error code to the application.

       MPI applications can also implement their own error handlers by calling:

       • MPI_Comm_create_errhandler then MPI_Comm_set_errhandler

       • MPI_File_create_errhandler then MPI_File_set_errhandler

       • MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init

       • MPI_Win_create_errhandler then MPI_Win_set_errhandler

       Note that MPI does not guarantee that an MPI program can continue past an error.

       See the MPImanpage for a full list of MPIerrorcodes.

       See the Error Handling section of the MPI-3.1 standard for more information.

       • fh: File handle (handle).

       • count: Number of elements in buffer (integer).

       • datatype: Data type of each buffer element (handle).

       • buf: Initial address of buffer (choice).

       • status: Status object (status).

       • ierror: Fortran only: Error status (integer).

CSyntax
          #include <mpi.h>

          int MPI_File_read_all(MPI_File fh, void *buf,
               int count, MPI_Datatype datatype, MPI_Status *status)

   FortranSyntax
          USE MPI
          ! or the older form: INCLUDE 'mpif.h'
          MPI_FILE_READ_ALL(FH, BUF, COUNT,
               DATATYPE, STATUS, IERROR)
               <type>  BUF(*)
               INTEGER FH, COUNT, DATATYPE, STATUS(MPI_STATUS_SIZE),IERROR

   Fortran2008Syntax
          USE mpi_f08
          MPI_File_read_all(fh, buf, count, datatype, status, ierror)
               TYPE(MPI_File), INTENT(IN) :: fh
               TYPE(*), DIMENSION(..) :: buf
               INTEGER, INTENT(IN) :: count
               TYPE(MPI_Datatype), INTENT(IN) :: datatype
               TYPE(MPI_Status) :: status
               INTEGER, OPTIONAL, INTENT(OUT) :: ierror