DOKK / manpages / debian 13 / openmpi-doc / MPI_File_set_size.openmpi.3.en
MPI_FILE_SET_SIZE(3) Open MPI MPI_FILE_SET_SIZE(3)

MPI_File_set_size — Resizes a file (collective).

#include <mpi.h>
int MPI_File_set_size(MPI_File fh, MPI_Offset size)



USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_FILE_SET_SIZE(FH, SIZE, IERROR)


     INTEGER FH, IERROR


     INTEGER(KIND=MPI_OFFSET_KIND)   SIZE



USE mpi_f08
MPI_File_set_size(fh, size, ierror)


     TYPE(MPI_File), INTENT(IN) :: fh


     INTEGER(KIND=MPI_OFFSET_KIND), INTENT(IN) :: size


     INTEGER, OPTIONAL, INTENT(OUT) :: ierror


  • fh: File handle (handle).
  • size: Size to truncate or expand file (integer).

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

MPI_File_set_size resizes the file associated with the file handle fh, truncating UNIX files as necessary. MPI_File_set_size is collective; all processes in the group must pass identical values for size.

When using MPI_File_set_size on a UNIX file, if size is larger than the current file size, the file size becomes size. If size is smaller than the current file size, the file is truncated at the position defined by size (from the beginning of the file and measured in bytes). Regions of the file which have been previously written are unaffected.

MPI_File_set_size does not affect the individual file pointers or the shared file pointer.

Note that the actual amount of storage space cannot be allocated by MPI_File_set_size. Use MPI_File_preallocate to accomplish this.

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 MPI man page for a full list of MPI error codes.

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

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February 17, 2025