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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="SNESSetUseMatrixFree"><H1>SNESSetUseMatrixFree</H1></A>
indicates that <A HREF="../SNES/SNES.html#SNES">SNES</A> should use matrix free finite difference matrix vector products internally to apply the Jacobian.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscsnes.h"
<A HREF="../Sys/PetscErrorCode.html#PetscErrorCode">PetscErrorCode</A> <A HREF="../SNES/SNESSetUseMatrixFree.html#SNESSetUseMatrixFree">SNESSetUseMatrixFree</A>(<A HREF="../SNES/SNES.html#SNES">SNES</A> snes,<A HREF="../Sys/PetscBool.html#PetscBool">PetscBool</A> mf_operator,<A HREF="../Sys/PetscBool.html#PetscBool">PetscBool</A> mf)
</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>- <A HREF="../SNES/SNES.html#SNES">SNES</A> context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>mf_operator </B></TD><TD>- use matrix-free only for the Amat used by <A HREF="../SNES/SNESSetJacobian.html#SNESSetJacobian">SNESSetJacobian</A>(), this means the user provided Pmat will continue to be used
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>mf </B></TD><TD>- use matrix-free for both the Amat and Pmat used by <A HREF="../SNES/SNESSetJacobian.html#SNESSetJacobian">SNESSetJacobian</A>(), both the Amat and Pmat set in <A HREF="../SNES/SNESSetJacobian.html#SNESSetJacobian">SNESSetJacobian</A>() will be ignored
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Options Database</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_mf </B></TD><TD>- use matrix free for both the mat and pmat operator
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_mf_operator </B></TD><TD>- use matrix free only for the mat operator
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_fd_color </B></TD><TD>- compute the Jacobian via coloring and finite differences.
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_fd </B></TD><TD>- compute the Jacobian via finite differences (slow)
</TD></TR></TABLE>
<P>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
<A HREF="../SNES/SNES.html#SNES">SNES</A> supports three approaches for computing (approximate) Jacobians: user provided via <A HREF="../SNES/SNESSetJacobian.html#SNESSetJacobian">SNESSetJacobian</A>(), matrix free, and computing explictly with
finite differences and coloring using <A HREF="../Mat/MatFDColoring.html#MatFDColoring">MatFDColoring</A>. It is also possible to use automatic differentiation and the <A HREF="../Mat/MatFDColoring.html#MatFDColoring">MatFDColoring</A> object.
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../SNES/SNESGetUseMatrixFree.html#SNESGetUseMatrixFree">SNESGetUseMatrixFree</A>(), <A HREF="../SNES/MatCreateSNESMF.html#MatCreateSNESMF">MatCreateSNESMF</A>(), <A HREF="../SNES/SNESComputeJacobianDefaultColor.html#SNESComputeJacobianDefaultColor">SNESComputeJacobianDefaultColor</A>()
<BR><P><B></B><H3><FONT COLOR="#CC3333">Level</FONT></H3>intermediate<BR>
<H3><FONT COLOR="#CC3333">Location</FONT></H3>
</B><A HREF="../../../src/snes/interface/snes.c.html#SNESSetUseMatrixFree">src/snes/interface/snes.c</A>
<BR><A HREF="./index.html">Index of all SNES routines</A>
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