MPI_File_read(3)

NAME
MPI_File_read - Reads a file starting at the location specified by the individual file pointer (blocking, noncollective).

SYNTAX

C Syntax
#include <mpi.h>
int MPI_File_read(MPI_File fh, void *buf,
	int count, MPI_Datatype datatype, MPI_Status *status)

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

Fortran 2008 Syntax
USE mpi_f08
MPI_File_read(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

INPUT PARAMETERS

fh  File handle (handle).

count
    Number of elements in buffer (integer).

datatype
    Data type of each buffer element (handle).

OUTPUT PARAMETERS

buf Initial address of buffer (integer).

status
    Status object (status).

IERROR
    Fortran only: Error status (integer).

DESCRIPTION
MPI_File_read 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 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.

ERRORS
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ functions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism will be used to throw an MPI::Exception object.

Before the error value is returned, the current MPI error handler is called. For MPI I/O function errors, the default error handler is set to MPI_ERRORS_RETURN. The error handler may be changed with MPI_File_set_errhandler; the predefined error handler MPI_ERRORS_ARE_FATAL may be used to make I/O errors fatal. Note that MPI does not guarantee that an MPI program can continue past an error.