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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML3.2 EN">
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<TITLE>KSPSetOperators</TITLE>
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<A NAME="KSPSetOperators"><H1>KSPSetOperators</H1></A>
Sets the matrix associated with the linear system and a (possibly) different one associated with the preconditioner.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscksp.h"
int KSPSetOperators(KSP ksp,Mat Amat,Mat Pmat,MatStructure flag)
</PRE>
Collective on <A HREF="../KSP/KSP.html#KSP">KSP</A> and <A HREF="../Mat/Mat.html#Mat">Mat</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>ksp </B></TD><TD>- the <A HREF="../KSP/KSP.html#KSP">KSP</A> context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>Amat </B></TD><TD>- the matrix associated with the linear system
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>Pmat </B></TD><TD>- the matrix to be used in constructing the preconditioner, usually the
same as Amat.
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>flag </B></TD><TD>- flag indicating information about the preconditioner matrix structure
during successive linear solves. This flag is ignored the first time a
linear system is solved, and thus is irrelevant when solving just one linear
system.
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
The flag can be used to eliminate unnecessary work in the preconditioner
during the repeated solution of linear systems of the same <A HREF="../Sys/size.html#size">size</A>. The
available options are
<pre>
SAME_PRECONDITIONER -
</pre>
<pre>
Pmat is identical during successive linear solves.
</pre>
<pre>
This option is intended for folks who are using
</pre>
<pre>
different Amat and Pmat matrices and want to reuse the
</pre>
<pre>
same preconditioner matrix. For example, this option
</pre>
<pre>
saves work by not recomputing incomplete factorization
</pre>
<pre>
for ILU/ICC preconditioners.
</pre>
<pre>
SAME_NONZERO_PATTERN -
</pre>
<pre>
Pmat has the same nonzero structure during
</pre>
<pre>
successive linear solves.
</pre>
<pre>
DIFFERENT_NONZERO_PATTERN -
</pre>
<pre>
Pmat does not have the same nonzero structure.
</pre>
<P>
<H3><FONT COLOR="#CC3333">Caution</FONT></H3>
If you specify SAME_NONZERO_PATTERN, PETSc believes your assertion
and does not check the structure of the matrix. If you erroneously
claim that the structure is the same when it actually is not, the new
preconditioner will not function correctly. Thus, use this optimization
feature carefully!
<P>
If in doubt about whether your preconditioner matrix has changed
structure or not, use the flag DIFFERENT_NONZERO_PATTERN.
<P>
<P>
<H3><FONT COLOR="#CC3333">Keywords</FONT></H3>
<A HREF="../KSP/KSP.html#KSP">KSP</A>, set, operators, matrix, preconditioner, linear system
<BR>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../KSP/KSPSolve.html#KSPSolve">KSPSolve</A>(), <A HREF="../KSP/KSPGetPC.html#KSPGetPC">KSPGetPC</A>(), <A HREF="../PC/PCGetOperators.html#PCGetOperators">PCGetOperators</A>(), <A HREF="../PC/PCSetOperators.html#PCSetOperators">PCSetOperators</A>()
<BR><P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>beginner
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/ksp/ksp/interface/itcreate.c.html#KSPSetOperators">src/ksp/ksp/interface/itcreate.c</A>
<BR><A HREF="./index.html">Index of all KSP 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/mat/examples/tutorials/ex3.c.html">src/mat/examples/tutorials/ex3.c.html</A><BR>
<A HREF="../../../src/ksp/pc/examples/tutorials/ex1.c.html">src/ksp/pc/examples/tutorials/ex1.c.html</A><BR>
<A HREF="../../../src/ksp/pc/examples/tutorials/ex2.c.html">src/ksp/pc/examples/tutorials/ex2.c.html</A><BR>
<A HREF="../../../src/ksp/examples/tutorials/ex1.c.html">src/ksp/examples/tutorials/ex1.c.html</A><BR>
<A HREF="../../../src/ksp/examples/tutorials/ex2.c.html">src/ksp/examples/tutorials/ex2.c.html</A><BR>
<A HREF="../../../src/ksp/examples/tutorials/ex3.c.html">src/ksp/examples/tutorials/ex3.c.html</A><BR>
<A HREF="../../../src/ksp/examples/tutorials/ex4.c.html">src/ksp/examples/tutorials/ex4.c.html</A><BR>
<A HREF="../../../src/ksp/examples/tutorials/ex5.c.html">src/ksp/examples/tutorials/ex5.c.html</A><BR>
<A HREF="../../../src/ksp/examples/tutorials/ex7.c.html">src/ksp/examples/tutorials/ex7.c.html</A><BR>
<A HREF="../../../src/ksp/examples/tutorials/ex8.c.html">src/ksp/examples/tutorials/ex8.c.html</A><BR>
<A HREF="../../../src/ksp/examples/tutorials/ex9.c.html">src/ksp/examples/tutorials/ex9.c.html</A><BR>
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