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<TITLE>PCFactorSetShiftPd</TITLE>
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<A NAME="PCFactorSetShiftPd"><H1>PCFactorSetShiftPd</H1></A>
specify whether to use Manteuffel shifting. If a matrix factorisation breaks down because of nonpositive pivots, adding sufficient identity to the diagonal will remedy this. Setting this causes a bisection method to find the minimum shift that will lead to a well-defined matrix factor.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscpc.h"
PetscErrorCode PETSCKSP_DLLEXPORT PCFactorSetShiftPd(PC pc,PetscTruth shift)
</PRE>
Collective on <A HREF="../PC/PC.html#PC">PC</A>
<P>
<H3><FONT COLOR="#CC3333">Input parameters</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>pc </B></TD><TD>- the preconditioner context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>shifting </B></TD><TD>- <A HREF="../Sys/PETSC_TRUE.html#PETSC_TRUE">PETSC_TRUE</A> to set shift else <A HREF="../Sys/PETSC_FALSE.html#PETSC_FALSE">PETSC_FALSE</A>
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Options Database Key</FONT></H3>
<DT><B>-pc_factor_shift_positive_definite [<A HREF="../Sys/PETSC_TRUE.html#PETSC_TRUE">PETSC_TRUE</A>/<A HREF="../Sys/PETSC_FALSE.html#PETSC_FALSE">PETSC_FALSE</A>] </B> -Activate/Deactivate <A HREF="../PC/PCFactorSetShiftPd.html#PCFactorSetShiftPd">PCFactorSetShiftPd</A>(); the value
is optional with <A HREF="../Sys/PETSC_TRUE.html#PETSC_TRUE">PETSC_TRUE</A> being the default
<br>
<P>
<P>
<H3><FONT COLOR="#CC3333">Keywords</FONT></H3>
<A HREF="../PC/PC.html#PC">PC</A>, indefinite, factorization
<BR>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../PC/PCFactorSetZeroPivot.html#PCFactorSetZeroPivot">PCFactorSetZeroPivot</A>(), <A HREF="../PC/PCFactorSetShiftNonzero.html#PCFactorSetShiftNonzero">PCFactorSetShiftNonzero</A>()
<BR><P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>intermediate
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/ksp/pc/impls/factor/factor.c.html#PCFactorSetShiftPd">src/ksp/pc/impls/factor/factor.c</A>
<BR><A HREF="./index.html">Index of all PC routines</A>
<BR><A HREF="../../index.html">Table of Contents for all manual pages</A>
<BR><A HREF="../singleindex.html">Index of all manual pages</A>
<P><H3><FONT COLOR="#CC3333">Examples</FONT></H3>
<A HREF="../../../src/ksp/pc/examples/tutorials/ex1.c.html">src/ksp/pc/examples/tutorials/ex1.c.html</A><BR>
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