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<div id="version" align=right><b>petsc-3.10.3 2018-12-18</b></div>
<div id="bugreport" align=right><a href="mailto:petsc-maint@mcs.anl.gov?subject=Typo or Error in Documentation &body=Please describe the typo or error in the documentation: petsc-3.10.3 v3.10.3 docs/manualpages/Tao/TaoDefaultComputeGradient.html "><small>Report Typos and Errors</small></a></div>
<A NAME="TaoDefaultComputeGradient"><H1>TaoDefaultComputeGradient</H1></A>
computes the gradient using finite differences.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petsctao.h"
<A HREF="../Sys/PetscErrorCode.html#PetscErrorCode">PetscErrorCode</A> <A HREF="../Tao/TaoDefaultComputeGradient.html#TaoDefaultComputeGradient">TaoDefaultComputeGradient</A>(<A HREF="../Tao/Tao.html#Tao">Tao</A> tao,<A HREF="../Vec/Vec.html#Vec">Vec</A> Xin,<A HREF="../Vec/Vec.html#Vec">Vec</A> G,void *dummy)
</PRE>
Collective on <A HREF="../Tao/Tao.html#Tao">Tao</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>tao </B></TD><TD>- the <A HREF="../Tao/Tao.html#Tao">Tao</A> context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>X </B></TD><TD>- compute gradient at this point
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>dummy </B></TD><TD>- not used
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Output Parameters</FONT></H3>
<DT><B>G </B> -Gradient Vector
<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>-tao_fd_gradient </B></TD><TD>- activates <A HREF="../Tao/TaoDefaultComputeGradient.html#TaoDefaultComputeGradient">TaoDefaultComputeGradient</A>()
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-tao_fd_delta <delta> </B></TD><TD>- change in X used to calculate finite differences
</TD></TR></TABLE>
<P>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
This routine is slow and expensive, and is not currently optimized
to take advantage of sparsity in the problem. Although
<A HREF="../Tao/TaoDefaultComputeGradient.html#TaoDefaultComputeGradient">TaoDefaultComputeGradient</A> is not recommended for general use
in large-scale applications, It can be useful in checking the
correctness of a user-provided gradient. Use the tao method TAOTEST
to get an indication of whether your gradient is correct.
This finite difference gradient evaluation can be set using the routine <A HREF="../Tao/TaoSetGradientRoutine.html#TaoSetGradientRoutine">TaoSetGradientRoutine</A>() or by using the command line option -tao_fd_gradient
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../Tao/TaoSetGradientRoutine.html#TaoSetGradientRoutine">TaoSetGradientRoutine</A>()
<BR><P><B></B><H3><FONT COLOR="#CC3333">Level</FONT></H3>advanced<BR>
<H3><FONT COLOR="#CC3333">Location</FONT></H3>
</B><A HREF="../../../src/tao/interface/fdiff.c.html#TaoDefaultComputeGradient">src/tao/interface/fdiff.c</A>
<BR><A HREF="./index.html">Index of all Tao routines</A>
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