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<H2><A NAME="SECTION000111000000000000000">
psb_precinit -- Initialize a  preconditioner</A>
</H2>

<P>
<PRE>
call psb_precinit(prec, ptype, info)
</PRE>

<P>
<DL>
<DT><STRONG>Type:</STRONG></DT>
<DD>Asynchronous.
</DD>
<DT><STRONG><B>On Entry</B></STRONG></DT>
<DD>
</DD>
<DT><STRONG>ptype</STRONG></DT>
<DD>the type of preconditioner. 
Scope: <B>global</B> 
<BR>
Type: <B>required</B>
<BR>
Intent: <B>in</B>.
<BR>
Specified as: a character string, see usage notes.
</DD>
<DT><STRONG><B>On Exit</B></STRONG></DT>
<DD><P>
</DD>
<DT><STRONG>prec</STRONG></DT>
<DD>Scope: <B>local</B> 
<BR>
Type: <B>required</B>
<BR>
Intent: <B>inout</B>.
<BR>
Specified as: a preconditioner data structure precdata<TT>psb_prec_type</TT>.
</DD>
<DT><STRONG>info</STRONG></DT>
<DD>Scope: <B>global</B> 
<BR>
Type: <B>required</B>
<BR>
Intent: <B>out</B>.
<BR>
Error code: if no error, 0 is returned.
</DD>
</DL>
<FONT SIZE="+1"><B>Notes</B></FONT>
Legal inputs to this subroutine are interpreted depending on the
<IMG
 WIDTH="42" HEIGHT="30" ALIGN="MIDDLE" BORDER="0"
 SRC="img139.png"
 ALT="$ptype$"> string as follows<A NAME="tex2html28"
  HREF="footnode.html#foot6720"><SUP>3</SUP></A>:
<DL>
<DT><STRONG>NONE</STRONG></DT>
<DD>No preconditioning, i.e. the preconditioner is just a copy
  operator.
</DD>
<DT><STRONG>DIAG</STRONG></DT>
<DD>Diagonal scaling; each entry of the input vector is
  multiplied by the reciprocal of the sum of the absolute values of
  the coefficients in the corresponding row of matrix  <IMG
 WIDTH="16" HEIGHT="14" ALIGN="BOTTOM" BORDER="0"
 SRC="img1.png"
 ALT="$A$">;
</DD>
<DT><STRONG>BJAC</STRONG></DT>
<DD>Precondition by a  factorization of the
  block-diagonal of matrix <IMG
 WIDTH="16" HEIGHT="14" ALIGN="BOTTOM" BORDER="0"
 SRC="img1.png"
 ALT="$A$">, where block boundaries are determined
  by the data allocation boundaries for each process; requires no
  communication. Only the incomplete factorization <IMG
 WIDTH="56" HEIGHT="32" ALIGN="MIDDLE" BORDER="0"
 SRC="img140.png"
 ALT="$ILU(0)$"> is
  currently implemented.  
</DD>
</DL>

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