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