80 строки
2.6 KiB
Groff
80 строки
2.6 KiB
Groff
.\"Copyright 2006, Sun Microsystems, Inc.
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.\" Copyright (c) 1996 Thinking Machines Corporation
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.TH MPI_Get_count 3OpenMPI "September 2006" "Open MPI 1.2" " "
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.SH NAME
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\fBMPI_Get_count \fP \- Gets the number of top-level elements received.
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.SH SYNTAX
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.ft R
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.SH C Syntax
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.nf
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#include <mpi.h>
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int MPI_Get_count(MPI_Status *\fIstatus\fP, MPI_Datatype\fI datatype\fP,
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int\fI *count\fP)
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.SH Fortran Syntax
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.nf
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INCLUDE 'mpif.h'
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MPI_GET_COUNT(\fISTATUS, DATATYPE, COUNT, IERROR\fP)
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INTEGER \fISTATUS(MPI_STATUS_SIZE), DATATYPE, COUNT, IERROR\fP
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.SH C++ Syntax
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.nf
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#include <mpi.h>
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int Status::Get_count(const Datatype& \fIdatatype\fP) const
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.SH INPUT PARAMETERS
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.ft R
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.TP 1i
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status
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Return status of receive operation (status).
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.TP 1i
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datatype
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Datatype of each receive 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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count
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Number of received elements (integer).
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.ft R
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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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Returns the number of entries received. (We count entries, each of type
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datatype, not bytes.) The datatype argument should match the argument
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provided by the receive call that set the status variable. (As explained in Section 3.12.5 in the MPI-1 Standard, "Use of General Datatypes in Communication," MPI_Get_count may, in certain situations, return the value MPI_UNDEFINED.)
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.sp
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The datatype argument is passed to MPI_Get_count to improve performance. A message might be received without counting the number of elements it contains, and the count value is often not needed. Also, this allows the same function to be used after a call to MPI_Probe.
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.SH NOTES
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If the size of the datatype is zero, this routine will return a count of
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zero. If the amount of data in
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.I status
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is not an exact multiple of the
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size of
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.I datatype
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(so that
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.I count
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would not be integral), a
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.I count
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of
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.I MPI_UNDEFINED
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is returned instead.
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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. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.
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.SH SEE ALSO
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.ft R
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.sp
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MPI_Get_elements
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