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<H2><A NAME="SECTION000111000000000000000">
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psb_precinit -- Initialize a preconditioner</A>
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</H2>
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<P>
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<PRE>
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call psb_precinit(prec, ptype, info)
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</PRE>
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<P>
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<DL>
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<DT><STRONG>Type:</STRONG></DT>
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<DD>Asynchronous.
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</DD>
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<DT><STRONG><B>On Entry</B></STRONG></DT>
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<DD>
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</DD>
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<DT><STRONG>ptype</STRONG></DT>
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<DD>the type of preconditioner.
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Scope: <B>global</B>
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<BR>
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Type: <B>required</B>
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<BR>
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Intent: <B>in</B>.
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<BR>
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Specified as: a character string, see usage notes.
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</DD>
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<DT><STRONG><B>On Exit</B></STRONG></DT>
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<DD><P>
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</DD>
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<DT><STRONG>prec</STRONG></DT>
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<DD>Scope: <B>local</B>
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<BR>
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Type: <B>required</B>
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<BR>
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Intent: <B>inout</B>.
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<BR>
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Specified as: a preconditioner data structure precdata<TT>psb_prec_type</TT>.
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</DD>
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<DT><STRONG>info</STRONG></DT>
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<DD>Scope: <B>global</B>
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<BR>
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Type: <B>required</B>
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<BR>
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Intent: <B>out</B>.
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<BR>
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Error code: if no error, 0 is returned.
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</DD>
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</DL>
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<FONT SIZE="+1"><B>Notes</B></FONT>
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Legal inputs to this subroutine are interpreted depending on the
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<IMG
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WIDTH="42" HEIGHT="30" ALIGN="MIDDLE" BORDER="0"
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SRC="img139.png"
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ALT="$ptype$"> string as follows<A NAME="tex2html28"
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HREF="footnode.html#foot6717"><SUP>3</SUP></A>:
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<DL>
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<DT><STRONG>NONE</STRONG></DT>
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<DD>No preconditioning, i.e. the preconditioner is just a copy
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operator.
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</DD>
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<DT><STRONG>DIAG</STRONG></DT>
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<DD>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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the coefficients in the corresponding row of matrix <IMG
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WIDTH="16" HEIGHT="14" ALIGN="BOTTOM" BORDER="0"
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SRC="img1.png"
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ALT="$A$">;
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</DD>
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<DT><STRONG>BJAC</STRONG></DT>
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<DD>Precondition by a factorization of the
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block-diagonal of matrix <IMG
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SRC="img1.png"
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ALT="$A$">, where block boundaries are determined
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by the data allocation boundaries for each process; requires no
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communication. Only the incomplete factorization <IMG
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WIDTH="56" HEIGHT="32" ALIGN="MIDDLE" BORDER="0"
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SRC="img140.png"
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ALT="$ILU(0)$"> is
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currently implemented.
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</DD>
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</DL>
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