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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="SNESLINESEARCHL2"><H1>SNESLINESEARCHL2</H1></A>
Secant search in the L2 norm of the function or the objective function, if it is provided with <A HREF="../SNES/SNESSetObjective.html#SNESSetObjective">SNESSetObjective</A>(). Attempts to solve min_lambda f(x + lambda y) using the secant method with the initial bracketing of lambda between [0,damping]. Differences of f()
are used to approximate the first and second derivative of f() with respect to lambda, f'() and f''(). The secant method is run for maxit iterations.
<P>
When an objective function is provided f(w) is the objective function otherwise f(w) = ||F(w)||^2. x is the current step and y is the search direction.
<P>
This has no checks on whether the secant method is actually converging.
<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_linesearch_max_it <maxit> </B></TD><TD>- maximum number of iterations, default is 1
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_linesearch_maxstep <length> </B></TD><TD>- the algorithm insures that a step length is never longer than this value
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_linesearch_damping <damping> </B></TD><TD>- initial step is scaled back by this factor, default is 1.0
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_linesearch_minlambda <minlambda> </B></TD><TD>- minimum allowable lambda
</TD></TR></TABLE>
<P>
<P>
Developer Notes: A better name for this method might be SNESLINESEARCHSECANT, L2 is not descriptive
<P>
<H3><FONT COLOR="#CC3333">Keywords</FONT></H3>
<A HREF="../SNES/SNES.html#SNES">SNES</A>, nonlinear, line search, norm, secant
<BR>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../SNES/SNESLINESEARCHBT.html#SNESLINESEARCHBT">SNESLINESEARCHBT</A>, <A HREF="../SNES/SNESLINESEARCHCP.html#SNESLINESEARCHCP">SNESLINESEARCHCP</A>, <A HREF="../SNES/SNESLineSearch.html#SNESLineSearch">SNESLineSearch</A>, <A HREF="../SNES/SNESLineSearchCreate.html#SNESLineSearchCreate">SNESLineSearchCreate</A>(), <A HREF="../SNES/SNESLineSearchSetType.html#SNESLineSearchSetType">SNESLineSearchSetType</A>()
<BR><P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>advanced
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/snes/linesearch/impls/l2/linesearchl2.c.html#SNESLINESEARCHL2">src/snes/linesearch/impls/l2/linesearchl2.c</A>
<BR><A HREF="./index.html">Index of all SNES routines</A>
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