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@ -3,28 +3,30 @@
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% \section{Preconditioners}
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% \section{Preconditioners}
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\label{sec:psprecs}
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\label{sec:psprecs}
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PSBLAS contains the implementation of many preconditioning
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The base PSBLAS library contains the implementation of two simple
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techniques some of which are very flexible thanks to the presence of
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preconditioning techniques:
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many parameters that is possible to adjust to fit the user's needs:
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\begin{itemize}
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\begin{itemize}
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\item Diagonal Scaling
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\item Diagonal Scaling
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\item Block Jacobi with ILU(0) factorization
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\item Block Jacobi with ILU(0) factorization
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%% \item Additive Schwarz with the Restricted Additive Schwarz and
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%% \item Additive Schwarz with the Restricted Additive Schwarz and
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%% Additive Schwarz with Harmonic extensions;
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%% Additive Schwarz with Harmonic extensions;
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\end{itemize}
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\end{itemize}
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The PSBLAS library is incorporating a package of two-level Additive
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The supporting data type and subroutine interfaces are defined in the
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Schwarz preconditioners called MD2P4; this is actually a family of
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module \verb|psb_prec_mod|.
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preconditioners since there is the possibility to choose between
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many variants, and is currently in an experimental state. Its
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%% We also provide a companion package of multi-level Additive
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documentation is planned to appear after stabilization of the
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%% Schwarz preconditioners called MD2P4; this is actually a family of
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package, which will characterize release 2.1 of our library.
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%% preconditioners since there is the possibility to choose between
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%% many variants, and is currently in an experimental stateIts
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%% documentation is planned to appear after stabilization of the
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%% package, which will characterize release 2.1 of our library.
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\subroutine{psb\_precset}{Sets the preconditioner type}
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\subroutine{psb\_precset}{Sets the preconditioner type}
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\syntax{call psb\_precset}{prec, ptype, info, iv, rs}
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\syntax{call psb\_precset}{prec, ptype, info}
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\begin{description}
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\begin{description}
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\item[\bf On Entry]
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\item[\bf On Entry]
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@ -36,14 +38,14 @@ Specified as: a pronditioner data structure \precdata.
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Scope: {\bf global} \\
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Scope: {\bf global} \\
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Type: {\bf required}\\
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Type: {\bf required}\\
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Specified as: a character string, see usage notes.
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Specified as: a character string, see usage notes.
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\item[iv] integer parameters for the precondtioner.
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%% \item[iv] integer parameters for the precondtioner.
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Scope: {\bf global} \\
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%% Scope: {\bf global} \\
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Type: {\bf required}\\
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%% Type: {\bf required}\\
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Specified as: an integer array, see usage notes.
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%% Specified as: an integer array, see usage notes.
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\item[rs]
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%% \item[rs]
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Scope: {\bf global} \\
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%% Scope: {\bf global} \\
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Type: {\bf optional}\\
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%% Type: {\bf optional}\\
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Specified as: a long precision real number.
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%% Specified as: a long precision real number.
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\item[\bf On Exit]
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\item[\bf On Exit]
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\item[info]
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\item[info]
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@ -52,10 +54,10 @@ Type: {\bf required}\\
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Error code: if no error, 0 is returned.
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Error code: if no error, 0 is returned.
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\end{description}
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\end{description}
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\section*{Usage Notes}
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\section*{Usage Notes}
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The PSBLAS 2.0 contains a number of preconditioners, ranging from a
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%% The PSBLAS 2.0 contains a number of preconditioners, ranging from a
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simple diagonal scaling to 2-level domain decomposition. These
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%% simple diagonal scaling to 2-level domain decomposition. These
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preconditioners may use the SuperLU or the UMFPACK software, if
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%% preconditioners may use the SuperLU or the UMFPACK software, if
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installed; see~\cite{SUPERLU,UMFPACK}.
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%% installed; see~\cite{SUPERLU,UMFPACK}.
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Legal inputs to this subroutine are interpreted depending on the
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Legal inputs to this subroutine are interpreted depending on the
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$ptype$ string as follows\footnote{The string is case-insensitive}:
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$ptype$ string as follows\footnote{The string is case-insensitive}:
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\begin{description}
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\begin{description}
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@ -64,7 +66,7 @@ $ptype$ string as follows\footnote{The string is case-insensitive}:
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\item[DIAG] Diagonal scaling; each entry of the input vector is
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\item[DIAG] Diagonal scaling; each entry of the input vector is
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multiplied by the reciprocal of the sum of the absolute values of
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multiplied by the reciprocal of the sum of the absolute values of
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the coefficients in the corresponding row of matrix $A$;
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the coefficients in the corresponding row of matrix $A$;
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\item[ILU] Precondition by the incomplete LU factorization of the
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\item[ILU, BJA] Precondition by the incomplete LU factorization of the
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block-diagonal of matrix $A$, where block boundaries are determined
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block-diagonal of matrix $A$, where block boundaries are determined
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by the data allocation boundaries for each process; requires no
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by the data allocation boundaries for each process; requires no
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communication. Only $ILU(0)$ is currently implemented.
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communication. Only $ILU(0)$ is currently implemented.
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Salvatore Filippone
18 years ago