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<div id="version" align=right><b>petsc-3.14.5 2021-03-03</b></div>
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<A NAME="MatCreateSNESMF"><H1>MatCreateSNESMF</H1></A>
Creates a matrix-free matrix context for use with a <A HREF="../SNES/SNES.html#SNES">SNES</A> solver. This matrix can be used as the Jacobian argument for the routine <A HREF="../SNES/SNESSetJacobian.html#SNESSetJacobian">SNESSetJacobian</A>(). See <A HREF="../Mat/MatCreateMFFD.html#MatCreateMFFD">MatCreateMFFD</A>() for details on how the finite difference computation is done.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscsnes.h"
#include "petscdm.h"
<A HREF="../Sys/PetscErrorCode.html#PetscErrorCode">PetscErrorCode</A> <A HREF="../SNES/MatCreateSNESMF.html#MatCreateSNESMF">MatCreateSNESMF</A>(<A HREF="../SNES/SNES.html#SNES">SNES</A> snes,<A HREF="../Mat/Mat.html#Mat">Mat</A> *J)
</PRE>
Collective on <A HREF="../SNES/SNES.html#SNES">SNES</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>snes </B></TD><TD>- the <A HREF="../SNES/SNES.html#SNES">SNES</A> context
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Output Parameter</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>J </B></TD><TD>- the matrix-free matrix
</TD></TR></TABLE>
<P>
<P>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
You can call <A HREF="../SNES/SNESSetJacobian.html#SNESSetJacobian">SNESSetJacobian</A>() with <A HREF="../SNES/MatMFFDComputeJacobian.html#MatMFFDComputeJacobian">MatMFFDComputeJacobian</A>() if you are using matrix and not a different
preconditioner matrix
<P>
If you wish to provide a different function to do differencing on to compute the matrix-free operator than
that provided to <A HREF="../SNES/SNESSetFunction.html#SNESSetFunction">SNESSetFunction</A>() then call <A HREF="../Mat/MatMFFDSetFunction.html#MatMFFDSetFunction">MatMFFDSetFunction</A>() with your function after this call.
<P>
The difference between this routine and <A HREF="../Mat/MatCreateMFFD.html#MatCreateMFFD">MatCreateMFFD</A>() is that this matrix
automatically gets the current base vector from the <A HREF="../SNES/SNES.html#SNES">SNES</A> object and not from an
explicit call to <A HREF="../Mat/MatMFFDSetBase.html#MatMFFDSetBase">MatMFFDSetBase</A>().
<P>
<H3><FONT COLOR="#CC3333">Warning</FONT></H3>
If <A HREF="../Mat/MatMFFDSetBase.html#MatMFFDSetBase">MatMFFDSetBase</A>() is ever called on jac then this routine will NO longer get
the x from the <A HREF="../SNES/SNES.html#SNES">SNES</A> object and <A HREF="../Mat/MatMFFDSetBase.html#MatMFFDSetBase">MatMFFDSetBase</A>() must from that point on be used to
change the base vector x.
<P>
<H3><FONT COLOR="#CC3333">Warning</FONT></H3>
Using a different function for the differencing will not work if you are using non-linear left preconditioning.
<P>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../Mat/MatDestroy.html#MatDestroy">MatDestroy</A>(), <A HREF="../Mat/MatMFFDSetFunction.html#MatMFFDSetFunction">MatMFFDSetFunction</A>(), <A HREF="../Mat/MatMFFDSetFunctionError.html#MatMFFDSetFunctionError">MatMFFDSetFunctionError</A>(), <A HREF="../Mat/MatMFFDDSSetUmin.html#MatMFFDDSSetUmin">MatMFFDDSSetUmin</A>()
<BR><A HREF="../Mat/MatMFFDSetHHistory.html#MatMFFDSetHHistory">MatMFFDSetHHistory</A>(), <A HREF="../Mat/MatMFFDResetHHistory.html#MatMFFDResetHHistory">MatMFFDResetHHistory</A>(), <A HREF="../Mat/MatCreateMFFD.html#MatCreateMFFD">MatCreateMFFD</A>(),
<A HREF="../Mat/MatMFFDGetH.html#MatMFFDGetH">MatMFFDGetH</A>(), <A HREF="../Mat/MatMFFDRegister.html#MatMFFDRegister">MatMFFDRegister</A>(), <A HREF="../SNES/MatMFFDComputeJacobian.html#MatMFFDComputeJacobian">MatMFFDComputeJacobian</A>(), <A HREF="../SNES/MatSNESMFSetReuseBase.html#MatSNESMFSetReuseBase">MatSNESMFSetReuseBase</A>(), <A HREF="../SNES/MatSNESMFGetReuseBase.html#MatSNESMFGetReuseBase">MatSNESMFGetReuseBase</A>()
<P>
<P><B></B><H3><FONT COLOR="#CC3333">Level</FONT></H3>advanced<BR>
<H3><FONT COLOR="#CC3333">Location</FONT></H3>
</B><A HREF="../../../src/snes/mf/snesmfj.c.html#MatCreateSNESMF">src/snes/mf/snesmfj.c</A>
<P><H3><FONT COLOR="#CC3333">Examples</FONT></H3>
<A HREF="../../../src/ts/tutorials/ex15.c.html">src/ts/tutorials/ex15.c.html</A><BR>
<BR><A HREF="./index.html">Index of all SNES routines</A>
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