109 строки
3.3 KiB
Groff
109 строки
3.3 KiB
Groff
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.\"Copyright 2006, Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.
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.\" Copyright (c) 1996 Thinking Machines Corporation
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.TH MPI_File_read_at 3OpenMPI "September 2006" "Open MPI 1.2" " "
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.SH NAME
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\fBMPI_File_read_at\fP \- Reads a file at an explicitly specified offset (blocking, noncollective).
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.SH SYNTAX
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.ft R
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.nf
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C Syntax
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#include <mpi.h>
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int MPI_File_read_at(MPI_File \fIfh\fP, MPI_Offset \fIoffset\fP,
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void \fI*buf\fP, int \fIcount\fP, MPI_Datatype \fIdatatype\fP,
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MPI_Status \fI*status\fP)
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Fortran Syntax (see FORTRAN 77 NOTES)
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INCLUDE 'mpif.h'
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MPI_FILE_READ_AT(\fIFH\fP, \fIOFFSET\fP, \fIBUF\fP, \fICOUNT\fP,
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\fI DATATYPE\fP, \fISTATUS\fP, \fIIERROR\fP)
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<type> \fIBUF\fP(*)
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INTEGER \fIFH, COUNT, DATATYPE, STATUS(MPI_STATUS_SIZE), IERROR\fP
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INTEGER(KIND=MPI_OFFSET_KIND) \fIOFFSET\fP
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.SH C++ Syntax
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.nf
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#include <mpi.h>
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void MPI::File::Read_at(MPI::Offset \fIoffset\fP, void* \fIbuf\fP,
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int \fIcount\fP, const MPI::Datatype& \fIdatatype\fP,
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MPI::Status& \fIstatus\fP)
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void MPI::File::Read_at(MPI::Offset \fIoffset\fP, void* \fIbuf\fP,
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int \fIcount\fP, const MPI::Datatype& \fIdatatype\fP)
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.SH INPUT PARAMETERS
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.ft R
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.TP 1i
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fh
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File handle (handle).
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.TP 1i
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offset
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File offset (integer).
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.TP 1i
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count
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Number of elements in buffer (integer).
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.TP 1i
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datatype
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Data type of each buffer element (handle).
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.SH OUTPUT PARAMETERS
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.ft R
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.TP 1i
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buf
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Initial address of buffer (choice).
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.TP 1i
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status
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Status object (status).
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.TP 1i
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IERROR
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Fortran only: Error status (integer).
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.SH DESCRIPTION
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.ft R
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MPI_File_read_at attempts to read from the file associated with
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.I fh
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(at the
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.I offset
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position) a total number of
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.I count
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data items having
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.I datatype
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type into the user's buffer
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.I buf.
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The
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.I offset
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is in
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.I etype
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units relative to the current view. That is, holes are not counted
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when locating an offset. The data is taken out of those parts of the
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file specified by the current view. MPI_File_read_at stores the
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number of
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.I datatype
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elements actually read in
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.I status.
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All other fields of
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.I status
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are undefined. It is erroneous to call this function if MPI_MODE_SEQUENTIAL mode was specified when the file was opened.
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.SH FORTRAN 77 NOTES
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.ft R
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The MPI standard prescribes portable Fortran syntax for
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the \fIOFFSET\fP argument only for Fortran 90. FORTRAN 77
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users may use the non-portable syntax
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.sp
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.nf
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INTEGER*MPI_OFFSET_KIND \fIOFFSET\fP
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.fi
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.sp
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where MPI_OFFSET_KIND is a constant defined in mpif.h
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and gives the length of the declared integer in bytes.
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.SH ERRORS
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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.
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.sp
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Before the error value is returned, the current MPI error handler is
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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.
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' @(#)MPI_File_read_at.3 1.28 06/03/09
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