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<H2><A NAME="SECTION00044000000000000000"></A>
<A NAME="sec:prec"></A>
<BR>
Preconditioner data structure
</H2>
Our base library  offers support for  simple well known preconditioners
like Diagonal Scaling or Block Jacobi with incomplete
factorization ILU(0). 

<P>
A preconditioner is held in the precdata<TT>    psb_prec_type</TT> data structure reported in 
figure&nbsp;<A HREF="#fig:prectype">6</A>. The <code>psb_prec_type</code> 
data type may contain a simple preconditioning matrix with the
associated communication descriptor.The values contained in
the <code>iprcparm</code> and <code>rprcparm</code> define tha type of
preconditioner along with all the parameters related to it; thus,
<code>iprcparm</code> and <code>rprcparm</code> define how the other records have
to be interpreted. This data structure is the basis of more complex
preconditioning strategies, which are the subject of further
research. 

<DIV ALIGN="CENTER"><A NAME="fig:prectype"></A><A NAME="674"></A>
<TABLE>
<CAPTION ALIGN="BOTTOM"><STRONG>Figure 6:</STRONG>
The PSBLAS defined data type that contains a preconditioner.</CAPTION>
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