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<div id="version" align=right><b>petsc-3.7.5 2017-01-01</b></div>
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<A NAME="SNESObjectiveComputeFunctionDefaultFD"><H1>SNESObjectiveComputeFunctionDefaultFD</H1></A>
Computes the gradient of a user provided objective
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
PetscErrorCode SNESObjectiveComputeFunctionDefaultFD(SNES snes,Vec X,Vec F,void *ctx)
</PRE>
Collective on <A HREF="../SNES/SNES.html#SNES">SNES</A>
<P>
<H3><FONT COLOR="#CC3333">Input Parameter</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>- the state vector
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>ctx </B></TD><TD>- the (ignored) function context
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Output Parameter</FONT></H3>
<DT><B>F </B> -the function value
<br>
<P>
<H3><FONT COLOR="#CC3333">Options Database Key</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_fd_function_eps </B></TD><TD>- The differencing parameter
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_fd_function </B></TD><TD>- Compute function from user provided objective with finite difference
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
<A HREF="../SNES/SNESObjectiveComputeFunctionDefaultFD.html#SNESObjectiveComputeFunctionDefaultFD">SNESObjectiveComputeFunctionDefaultFD</A> is similar in character to <A HREF="../SNES/SNESComputeJacobianDefault.html#SNESComputeJacobianDefault">SNESComputeJacobianDefault</A>.
Therefore, it should be used for debugging purposes only. Using it in conjunction with
<A HREF="../SNES/SNESComputeJacobianDefault.html#SNESComputeJacobianDefault">SNESComputeJacobianDefault</A> is excessively costly and produces a Jacobian that is quite
noisy. This is often necessary, but should be done with a grain of salt, even when debugging
small problems.
<P>
Note that this uses quadratic interpolation of the objective to form each value in the function.
<P>
<P>
<H3><FONT COLOR="#CC3333">Keywords</FONT></H3>
<A HREF="../SNES/SNES.html#SNES">SNES</A>, objective, debugging, finite differences, function
<BR>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../SNES/SNESSetFunction.html#SNESSetFunction">SNESSetFunction</A>(), <A HREF="../SNES/SNESComputeObjective.html#SNESComputeObjective">SNESComputeObjective</A>(), <A HREF="../SNES/SNESComputeJacobianDefault.html#SNESComputeJacobianDefault">SNESComputeJacobianDefault</A>()
<BR><P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>advanced
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/snes/interface/snesob.c.html#SNESObjectiveComputeFunctionDefaultFD">src/snes/interface/snesob.c</A>
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