Add GPU references and example to docs: first round.

docs/src/gettingstarted.tex

@@ -416,6 +416,45 @@ call P%build(A,desc_A,info)
 \end{listing}
 
 
+
+\subsection{GPU example\label{sec:gpu-example}}
+
+The code reported in Figure~\ref{fig:gpu-ex1} shows how to set  up a
+program exploiting the combined GPU capabilities of PSBLAS and
+AMG4PSBLAS.
+\begin{listing}[h!]
+\ifpdf
+\begin{minted}[breaklines=true,bgcolor=bg,fontsize=\small]{fortran}
+! build a one-level RAS with overlap 2 and ILU(0) on the local blocks.
+call P%init('AS',info)
+call P%set('SUB_OVR',2,info)
+call P%build(A,desc_A,info)
+... ...
+! solve Ax=b with preconditioned BiCGSTAB
+  call psb_krylov('BICGSTAB',A,P,b,x,tol,desc_A,info)
+\end{minted}
+\else
+\begin{center}
+\begin{minipage}{.90\textwidth}
+{\small
+\begin{verbatim}
+! build a one-level RAS with overlap 2 and ILU(0) on the local blocks.
+call P%init('AS',info)
+call P%set('SUB_OVR',2,info)
+call P%build(A,desc_A,info)
+... ...
+! solve Ax=b with preconditioned BiCGSTAB
+  call psb_krylov('BICGSTAB',A,P,b,x,tol,desc_A,info)
+\end{verbatim}
+}
+\end{minipage}
+\end{center}
+\fi
+\caption{setup of a one-level Schwarz preconditioner.\label{fig:gpu-ex1}}
+\end{listing}
+
+
+
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