plucky (3) MPI_File_iread_at.openmpi.3.gz
SYNTAX
C Syntax
#include <mpi.h>
int MPI_File_iread_at(MPI_File fh, MPI_Offset offset,
void *buf, int count, MPI_Datatype datatype,
MPI_Request *request)
Fortran Syntax
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_FILE_IREAD_AT(FH, OFFSET, BUF, COUNT, DATATYPE, REQUEST, IERROR)
<type> BUF(*)
INTEGER FH, COUNT, DATATYPE, REQUEST, IERROR
INTEGER(KIND=MPI_OFFSET_KIND) OFFSET
Fortran 2008 Syntax
USE mpi_f08
MPI_File_iread_at(fh, offset, buf, count, datatype, request, ierror)
TYPE(MPI_File), INTENT(IN) :: fh
INTEGER(KIND=MPI_OFFSET_KIND), INTENT(IN) :: offset
TYPE(*), DIMENSION(..), ASYNCHRONOUS :: buf
INTEGER, INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Request), INTENT(OUT) :: request
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
INPUT PARAMETERS
• fh: File handle (handle).
• offset: File offset (integer).
• count: Number of elements in the buffer (integer).
• datatype: Data type of each buffer element (handle).
OUTPUT PARAMETERS
• buf: Initial address of the buffer (choice).
• request: Request object (handle).
• ierror: Fortran only: Error status (integer).
DESCRIPTION
MPI_File_iread_at is the nonblocking version of MPI_File_read_at.
MPI_File_iread_at is a nonblocking 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. MPI_File_iread_at
stores the number of datatype elements actually read in status. All other fields of status are undefined.
ERRORS
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.
COPYRIGHT
2003-2025, The Open MPI Community
Feb 17, 2025 MPI_FILE_IREAD_AT(3)