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<H2><A NAME="SECTION00043000000000000000"></A>
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<A NAME="sec:prec"></A>
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Preconditioner data structure
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</H2>
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Our base library offers support for simple well known preconditioners
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like Diagonal Scaling or Block Jacobi with incomplete
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factorization ILU(0).
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<P>
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A preconditioner is held in the precdata<TT> psb_prec_type</TT> data structure reported in
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figure <A HREF="#fig:prectype">5</A>. The <code>psb_prec_type</code>
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data type may contain a simple preconditioning matrix with the
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associated communication descriptor.The values contained in
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the <code>iprcparm</code> and <code>rprcparm</code> define tha type of
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preconditioner along with all the parameters related to it; thus,
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<code>iprcparm</code> and <code>rprcparm</code> define how the other records have
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to be interpreted. This data structure is the basis of more complex
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preconditioning strategies, which are the subject of further
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research.
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<DIV ALIGN="CENTER"><A NAME="fig:prectype"></A><A NAME="624"></A>
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<TABLE>
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<CAPTION ALIGN="BOTTOM"><STRONG>Figure 5:</STRONG>
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The PSBLAS defined data type that contains a preconditioner.</CAPTION>
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