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<TITLE>SNESComputeJacobian</TITLE>
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<A NAME="SNESComputeJacobian"><H1>SNESComputeJacobian</H1></A>
Computes the Jacobian matrix that has been set with <A HREF="../SNES/SNESSetJacobian.html#SNESSetJacobian">SNESSetJacobian</A>().
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscsnes.h"
PetscErrorCode SNESComputeJacobian(SNES snes,Vec X,Mat *A,Mat *B,MatStructure *flg)
</PRE>
Collective on <A HREF="../SNES/SNES.html#SNES">SNES</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>snes </B></TD><TD>- the <A HREF="../SNES/SNES.html#SNES">SNES</A> context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>x </B></TD><TD>- input vector
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Output Parameters</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>A </B></TD><TD>- Jacobian matrix
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>B </B></TD><TD>- optional preconditioning matrix
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>flag </B></TD><TD>- flag indicating matrix structure (one of, SAME_NONZERO_PATTERN,DIFFERENT_NONZERO_PATTERN,SAME_PRECONDITIONER)
</TD></TR></TABLE>
<P>
<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>-snes_lag_preconditioner <lag></B></TD><TD>- . -snes_lag_jacobian <lag>
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_compare_explicit </B></TD><TD>- Compare the computed Jacobian to the finite difference Jacobian and output the differences
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_compare_explicit_draw </B></TD><TD>- Compare the computed Jacobian to the finite difference Jacobian and draw the result
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_compare_explicit_contour </B></TD><TD>- Compare the computed Jacobian to the finite difference Jacobian and draw a contour plot with the result
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_compare_operator </B></TD><TD>- Make the comparison options above use the operator instead of the preconditioning matrix
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
Most users should not need to explicitly call this routine, as it
is used internally within the nonlinear solvers.
<P>
See <A HREF="../KSP/KSPSetOperators.html#KSPSetOperators">KSPSetOperators</A>() for important information about setting the
flag parameter.
<P>
<P>
<H3><FONT COLOR="#CC3333">Keywords</FONT></H3>
<A HREF="../SNES/SNES.html#SNES">SNES</A>, compute, Jacobian, matrix
<BR>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../SNES/SNESSetJacobian.html#SNESSetJacobian">SNESSetJacobian</A>(), <A HREF="../KSP/KSPSetOperators.html#KSPSetOperators">KSPSetOperators</A>(), <A HREF="../Mat/MatStructure.html#MatStructure">MatStructure</A>, <A HREF="../SNES/SNESSetLagPreconditioner.html#SNESSetLagPreconditioner">SNESSetLagPreconditioner</A>(), <A HREF="../SNES/SNESSetLagJacobian.html#SNESSetLagJacobian">SNESSetLagJacobian</A>()
<BR><P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>developer
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/snes/interface/snes.c.html#SNESComputeJacobian">src/snes/interface/snes.c</A>
<BR><A HREF="./index.html">Index of all SNES 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/snes/examples/tutorials/ex45.c.html">src/snes/examples/tutorials/ex45.c.html</A><BR>
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