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<div id="version" align=right><b>petsc-3.14.5 2021-03-03</b></div>
<div id="bugreport" align=right><a href="mailto:petsc-maint@mcs.anl.gov?subject=Typo or Error in Documentation &body=Please describe the typo or error in the documentation: petsc-3.14.5 v3.14.5 docs/manualpages/PC/PCICC.html "><small>Report Typos and Errors</small></a></div>
<A NAME="PCICC"><H1>PCICC</H1></A>
Incomplete Cholesky factorization preconditioners.
<H3><FONT COLOR="#CC3333">Options Database Keys</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_factor_levels <k> </B></TD><TD>- number of levels of fill for ICC(k)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_factor_in_place </B></TD><TD>- only for ICC(0) with natural ordering, reuses the space of the matrix for
its factorization (overwrites original matrix)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_factor_fill <nfill> </B></TD><TD>- expected amount of fill in factored matrix compared to original matrix, nfill > 1
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_factor_mat_ordering_type <natural,nd,1wd,rcm,qmd> </B></TD><TD>- set the row/column ordering of the factored matrix
</TD></TR></TABLE>
<P>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
Only implemented for some matrix formats. Not implemented in parallel.
<P>
For BAIJ matrices this implements a point block ICC.
<P>
The Manteuffel shift is only implemented for matrices with block size 1
<P>
By default, the Manteuffel is applied (for matrices with block size 1). Call <A HREF="../PC/PCFactorSetShiftType.html#PCFactorSetShiftType">PCFactorSetShiftType</A>(pc,MAT_SHIFT_POSITIVE_DEFINITE);
to turn off the shift.
<P>
<H3><FONT COLOR="#CC3333">References</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>1. </B></TD><TD>- TONY F. CHAN AND HENK A. VAN DER VORST, Review article: APPROXIMATE AND INCOMPLETE FACTORIZATIONS,
Chapter in Parallel Numerical Algorithms, edited by D. Keyes, A. Semah, V. Venkatakrishnan, ICASE/LaRC Interdisciplinary Series in
Science and Engineering, Kluwer.
</TD></TR></TABLE>
<P>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../PC/PCCreate.html#PCCreate">PCCreate</A>(), <A HREF="../PC/PCSetType.html#PCSetType">PCSetType</A>(), <A HREF="../PC/PCType.html#PCType">PCType</A> (for list of available types), <A HREF="../PC/PC.html#PC">PC</A>, <A HREF="../PC/PCSOR.html#PCSOR">PCSOR</A>, <A HREF="../Mat/MatOrderingType.html#MatOrderingType">MatOrderingType</A>,
<BR><A HREF="../PC/PCFactorSetZeroPivot.html#PCFactorSetZeroPivot">PCFactorSetZeroPivot</A>(), <A HREF="../PC/PCFactorSetShiftType.html#PCFactorSetShiftType">PCFactorSetShiftType</A>(), <A HREF="../PC/PCFactorSetShiftAmount.html#PCFactorSetShiftAmount">PCFactorSetShiftAmount</A>(),
<A HREF="../PC/PCFactorSetFill.html#PCFactorSetFill">PCFactorSetFill</A>(), <A HREF="../PC/PCFactorSetMatOrderingType.html#PCFactorSetMatOrderingType">PCFactorSetMatOrderingType</A>(), <A HREF="../PC/PCFactorSetReuseOrdering.html#PCFactorSetReuseOrdering">PCFactorSetReuseOrdering</A>(),
<A HREF="../PC/PCFactorSetLevels.html#PCFactorSetLevels">PCFactorSetLevels</A>()
<P>
<P><B></B><H3><FONT COLOR="#CC3333">Level</FONT></H3>beginner<BR>
<H3><FONT COLOR="#CC3333">Location</FONT></H3>
</B><A HREF="../../../src/ksp/pc/impls/factor/icc/icc.c.html#PCICC">src/ksp/pc/impls/factor/icc/icc.c</A>
<P><H3><FONT COLOR="#CC3333">Examples</FONT></H3>
<A HREF="../../../src/ksp/pc/tutorials/ex2.c.html">src/ksp/pc/tutorials/ex2.c.html</A><BR>
<BR><A HREF="./index.html">Index of all PC routines</A>
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