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460 lines
14 KiB
TeX
460 lines
14 KiB
TeX
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\section{Parallel environment routines}
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\label{sec:parenv}
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\subroutine{psb\_init}{Initializes PSBLAS parallel environment}
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\syntax{call psb\_init}{icontxt, np}
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This subroutine initializes the PSBLAS parallel environment, defining
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a virtual parallel machine.
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\begin{description}
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\item[\bf On Entry ]
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\item[np] Number of processes in the PSBLAS virtual parallel machine.\\
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Scope:{\bf global}.\\
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Type:{\bf optional}.\\
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Specified as: an integer value. \
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Default: use all available processes provided by the underlying
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parallel environment.
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\end{description}
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\begin{description}
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\item[\bf On Return]
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\item[icontxt] the communication context identifying the virtual
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parallel machine.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer variable.
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\end{description}
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\section*{Notes}
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\begin{enumerate}
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\item A call to this routine must precede any other PSBLAS call.
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\item It is an error to specify a value for $np$ greater than the
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number of processes available in the underlying parallel execution
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environment.
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\end{enumerate}
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\subroutine{psb\_info}{Return information about PSBLAS parallel environment}
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\syntax{call psb\_info}{icontxt, iam, np}
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This subroutine returns informantion about the PSBLAS parallel environment, defining
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a virtual parallel machine.
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\begin{description}
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\item[\bf On Entry ]
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\item[icontxt] the communication context identifying the virtual
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parallel machine.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer variable.
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\end{description}
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\begin{description}
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\item[\bf On Return]
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\item[iam] Identifier of current process in the PSBLAS virtual parallel machine.\\
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Scope:{\bf local}.\\
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Type:{\bf required}.\\
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Specified as: an integer value. $-1 \le iam \le np-1$\
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\item[np] Number of processes in the PSBLAS virtual parallel machine.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer variable. \
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\end{description}
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\section*{Notes}
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\begin{enumerate}
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\item For processes in the virtual parallel machine the identifier
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will satisfy $0 \le iam \le np-1$;
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\item If the user has requested on \verb|psb_init| a number of
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processes less than the total available in the parallel execution
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environment, the remaining processes will have on return $iam=-1$;
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the only call involving \verb|icontxt| that any such process may
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execute is to \verb|psb_exit|.
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\end{enumerate}
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\subroutine{psb\_exit}{Exit from PSBLAS parallel environment}
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\syntax{call psb\_exit}{icontxt}
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\syntax*{call psb\_exit}{icontxt,close}
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This subroutine exits from the PSBLAS parallel virtual machine.
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\begin{description}
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\item[\bf On Entry ]
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\item[icontxt] the communication context identifying the virtual
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parallel machine.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer variable.
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\item[close] Whether to close all data structures related to the
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virtual parallel machine, besides those associated with icontxt.\\
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Scope:{\bf global}.\\
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Type:{\bf optional}.\\
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Specified as: a logical variable, default value: true.
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\end{description}
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\section*{Notes}
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\begin{enumerate}
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\item This routine may be called even if a previous call to
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\verb|psb_info| has returned with $iam=-1$; indeed, it it is the only
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routine that may be called with argument \verb|icontxt| in this
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situation.
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\item If the user wants to use multiple communication contexts in the
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same program, this routine may be called multiple times to
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selectively close the contexts with \verb|close=.false.|, while on
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the last call it should be called with \verb|close=.true.| to
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shutdown in a clean way the entire parallel environment.
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\end{enumerate}
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\subroutine{psb\_get\_mpicomm}{Get the MPI communicator}
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\syntax{call psb\_get\_mpicomm}{icontxt, icomm}
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This subroutine returns the MPI communicator associated with a PSBLAS context
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\begin{description}
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\item[\bf On Entry ]
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\item[icontxt] the communication context identifying the virtual
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parallel machine.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer variable.
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\end{description}
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\begin{description}
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\item[\bf On Return]
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\item[icomm] The MPI communicator associated with the PSBLAS virtual parallel machine.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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\end{description}
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\subroutine{psb\_get\_rank}{Get the MPI rank}
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\syntax{call psb\_get\_rank}{rank, icontxt, id}
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This subroutine returns the MPI rank of the PSBLAS process $id$
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\begin{description}
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\item[\bf On Entry ]
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\item[icontxt] the communication context identifying the virtual
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parallel machine.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer variable.
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\item[id] Identifier of a process in the PSBLAS virtual parallel machine.\\
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Scope:{\bf local}.\\
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Type:{\bf required}.\\
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Specified as: an integer value. $0 \le id \le np-1$\
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\end{description}
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\begin{description}
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\item[\bf On Return]
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\item[rank] The MPI rank associated with the PSBLAS process $id$.\\
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Scope:{\bf local}.\\
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Type:{\bf required}.\\
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\end{description}
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\subroutine{psb\_wtime}{Wall clock timing}
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\syntax{time = psb\_wtime}{}
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This function returns a wall clock timer. The resolution of the timer
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is dependent on the underlying parallel environment implementation.
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\begin{description}
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\item[\bf On Exit ]
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\item[Function value] the elapsed time in seconds.\\
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Returned as: a \verb|real(kind(1.d0))| integer variable.
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\end{description}
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\subroutine{psb\_barrier}{Sinchronization point parallel environment}
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\syntax{call psb\_barrier}{icontxt}
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This subroutine acts as a synchronization point for the PSBLAS
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parallel virtual machine. As such, it must be called by all
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participating processes.
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\begin{description}
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\item[\bf On Entry ]
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\item[icontxt] the communication context identifying the virtual
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parallel machine.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer variable.
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\end{description}
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\subroutine{psb\_abort}{Abort a computation}
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\syntax{call psb\_abort}{icontxt}
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This subroutine aborts computation on the parallel virtual machine.
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\begin{description}
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\item[\bf On Entry ]
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\item[icontxt] the communication context identifying the virtual
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parallel machine.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer variable.
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\end{description}
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\subroutine{psb\_bcast}{Broadcast data}
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\syntax{call psb\_bcast}{icontxt, dat, root}
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This subroutine implements a broadcast operation based on the
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underlying communication library.
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\begin{description}
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\item[\bf On Entry ]
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\item[icontxt] the communication context identifying the virtual
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parallel machine.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer variable.
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\item[dat] On the root process, the data to be broadcast.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer, real or complex variable, which may be a
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scalar, or a rank 1 or 2 array, or a character or logical scalar. \
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Type, rank and size must agree on all processes.
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\item[root] Root process holding data to be broadcast.\\
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Scope:{\bf global}.\\
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Type:{\bf optional}.\\
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Specified as: an integer value $0<= root <= np-1$, default 0 \
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\end{description}
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\begin{description}
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\item[\bf On Return]
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\item[dat] On processes other than root, the data to be broadcast.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer, real or complex variable, which may be a
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scalar, or a rank 1 or 2 array, or a character or logical scalar. \
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Type, rank and size must agree on all processes.
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\end{description}
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\subroutine{psb\_sum}{Global sum}
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\syntax{call psb\_sum}{icontxt, dat, root}
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This subroutine implements a sum reduction operation based on the
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underlying communication library.
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\begin{description}
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\item[\bf On Entry ]
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\item[icontxt] the communication context identifying the virtual
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parallel machine.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer variable.
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\item[dat] The local contribution to the global sum.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer, real or complex variable, which may be a
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scalar, or a rank 1 or 2 array. \
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Type, rank and size must agree on all processes.
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\item[root] Process to hold the final sum, or $-1$ to make it available
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on all processes.\\
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Scope:{\bf global}.\\
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Type:{\bf optional}.\\
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Specified as: an integer value $-1<= root <= np-1$, default -1. \
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\end{description}
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\begin{description}
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\item[\bf On Return]
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\item[dat] On destination process(es), the result of the sum operation.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer, real or complex variable, which may be a
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scalar, or a rank 1 or 2 array. \\
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Type, rank and size must agree on all processes.
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\end{description}
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\section*{Notes}
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\begin{enumerate}
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\item The \verb|dat| argument is both input and output, and its
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value may be changed even on processes different from the final
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result destination.
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\end{enumerate}
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\subroutine{psb\_amx}{Global maximum absolute value}
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\syntax{call psb\_amx}{icontxt, dat, root}
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This subroutine implements a maximum absolute value reduction
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operation based on the underlying communication library.
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\begin{description}
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\item[\bf On Entry ]
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\item[icontxt] the communication context identifying the virtual
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parallel machine.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer variable.
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\item[dat] The local contribution to the global maximum.\\
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Scope:{\bf local}.\\
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Type:{\bf required}.\\
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Specified as: an integer, real or complex variable, which may be a
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scalar, or a rank 1 or 2 array. \
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Type, rank and size must agree on all processes.
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\item[root] Process to hold the final sum, or $-1$ to make it available
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on all processes.\\
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Scope:{\bf global}.\\
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Type:{\bf optional}.\\
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Specified as: an integer value $-1<= root <= np-1$, default -1. \\
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\end{description}
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\begin{description}
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\item[\bf On Return]
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\item[dat] On destination process(es), the result of the maximum operation.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer, real or complex variable, which may be a
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scalar, or a rank 1 or 2 array. \
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Type, rank and size must agree on all processes.
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\end{description}
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\section*{Notes}
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\begin{enumerate}
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\item The \verb|dat| argument is both input and output, and its
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value may be changed even on processes different from the final
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result destination.
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\end{enumerate}
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\subroutine{psb\_amn}{Global minimum absolute value}
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\syntax{call psb\_amn}{icontxt, dat, root}
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This subroutine implements a minimum absolute value reduction
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operation based on the underlying communication library.
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\begin{description}
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\item[\bf On Entry ]
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\item[icontxt] the communication context identifying the virtual
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parallel machine.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer variable.
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\item[dat] The local contribution to the global minimum.\\
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Scope:{\bf local}.\\
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Type:{\bf required}.\\
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Specified as: an integer, real or complex variable, which may be a
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scalar, or a rank 1 or 2 array. \
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Type, rank and size must agree on all processes.
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\item[root] Process to hold the final sum, or $-1$ to make it available
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on all processes.\\
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Scope:{\bf global}.\\
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Type:{\bf optional}.\\
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Specified as: an integer value $-1<= root <= np-1$, default -1. \\
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\end{description}
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\begin{description}
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\item[\bf On Return]
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\item[dat] On destination process(es), the result of the minimum operation.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer, real or complex variable, which may be a
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scalar, or a rank 1 or 2 array. \\
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Type, rank and size must agree on all processes.
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\end{description}
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\section*{Notes}
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\begin{enumerate}
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\item The \verb|dat| argument is both input and output, and its
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value may be changed even on processes different from the final
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result destination.
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\end{enumerate}
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\subroutine{psb\_snd}{Send data}
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\syntax{call psb\_snd}{icontxt, dat, dst, m}
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This subroutine sends a packet of data to a destination.
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\begin{description}
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\item[\bf On Entry ]
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\item[icontxt] the communication context identifying the virtual
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parallel machine.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer variable.
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\item[dat] The data to be sent.\\
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Scope:{\bf local}.\\
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Type:{\bf required}.\\
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Specified as: an integer, real or complex variable, which may be a
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scalar, or a rank 1 or 2 array, or a character or logical scalar. \
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Type and rank must agree on sender and receiver process; if $m$ is
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not specified, size must agree as well.
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\item[dst] Destination process.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer value $0<= dst <= np-1$. \\
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\item[m] Number of rows.\\
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Scope:{\bf global}.\\
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Type:{\bf Optional}.\\
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Specified as: an integer value $0<= m <= size(dat,1)$. \\
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When $dat$ is a rank 2 array, specifies the number of rows to be sent
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independently of the leading dimension $size(dat,1)$; must have the
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same value on sending and receiving processes.
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\end{description}
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\begin{description}
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\item[\bf On Return]
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\end{description}
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\subroutine{psb\_rcv}{Receive data}
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\syntax{call psb\_rcv}{icontxt, dat, src, m}
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This subroutine receives a packet of data to a destination.
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\begin{description}
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\item[\bf On Entry ]
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\item[icontxt] the communication context identifying the virtual
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parallel machine.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer variable.
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\item[src] Source process.\\
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Scope:{\bf global}.\\
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Type:{\bf required}.\\
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Specified as: an integer value $0<= src <= np-1$. \\
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\item[m] Number of rows.\\
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Scope:{\bf global}.\\
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Type:{\bf Optional}.\\
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Specified as: an integer value $0<= m <= size(dat,1)$. \\
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When $dat$ is a rank 2 array, specifies the number of rows to be sent
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independently of the leading dimension $size(dat,1)$; must have the
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same value on sending and receiving processes.
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\end{description}
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\begin{description}
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\item[\bf On Return]
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\item[dat] The data to be received.\\
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Scope:{\bf local}.\\
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Type:{\bf required}.\\
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Specified as: an integer, real or complex variable, which may be a
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scalar, or a rank 1 or 2 array, or a character or logical scalar. \
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Type and rank must agree on sender and receiver process; if $m$ is
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not specified, size must agree as well.
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\end{description}
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