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MPI_File_read_at.3.rst

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MPI_File_read_at

:ref:`MPI_File_read_at` |mdash| Reads a file at an explicitly specified offset (blocking, noncollective).

SYNTAX

C Syntax

#include <mpi.h>

int MPI_File_read_at(MPI_File fh, MPI_Offset offset,
     void *buf, int count, MPI_Datatype datatype,
     MPI_Status *status)

Fortran Syntax

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

Fortran 2008 Syntax

USE mpi_f08
MPI_File_read_at(fh, offset, buf, count, datatype, status, ierror)
     TYPE(MPI_File), INTENT(IN) :: fh
     INTEGER(KIND=MPI_OFFSET_KIND), INTENT(IN) :: offset
     TYPE(*), DIMENSION(..) :: buf
     INTEGER, INTENT(IN) :: count
     TYPE(MPI_Datatype), INTENT(IN) :: datatype
     TYPE(MPI_Status) :: status
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS

  • fh: File handle (handle).
  • offset: File offset (integer).
  • count: Number of elements in buffer (integer).
  • datatype: Data type of each buffer element (handle).

OUTPUT PARAMETERS

  • buf: Initial address of buffer (choice).
  • status: Status object (status).
  • ierror: Fortran only: Error status (integer).

DESCRIPTION

:ref:`MPI_File_read_at` 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. :ref:`MPI_File_read_at` stores the number of datatype 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.

ERRORS