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<HTML>
<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
</CENTER>
<HR>
<H3>min_modify command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>min_modify keyword values ...
</PRE>
<UL><LI>one or more keyword/value pairs may be listed
<PRE>keyword = <I>linestyle</I> or <I>dmin</I> or <I>dmax</I> or <I>lineiter</I>
<I>linestyle</I> value = <I>secant</I> or <I>scan</I>
<I>dmin</I> value = min
min = minimum distance for line search to move (distance units)
<I>dmax</I> value = max
max = maximum distance for line search to move (distance units)
<I>lineiter</I> value = N
N = max number of iterations in a line search
</PRE>
</UL>
<P><B>Examples:</B>
</P>
<PRE>min_modify linestyle scan dmin 0.001 dmax 0.2
min_modify lineiter 5
</PRE>
<P><B>Description:</B>
</P>
<P>This command sets parameters that affect the minimization algorithms.
The various settings may effect the convergence rate and overall
number of force evaulations required by a minimization, so users can
experiment with these parameters to tune their minimizations.
</P>
<P>The <I>linestyle</I> sets the algorithm used for 1d line searches at each
outer iteration of the minimizer. The <I>secant</I> style uses two
successive force/energy evaluations to create a parabola and pick its
minimum as an estimate of the next iteration's 1d minimum. The <I>scan</I>
style starts its 1d search at <I>dmin</I> and doubles the distance along
the line at which the energy is computed until the minimum is passed.
It continues only as far as <I>dmax</I>. Normally, the <I>secant</I> method
should find more accurate 1d minimums in less iterations, but the
<I>scan</I> method can be more robust.
</P>
<P>The <I>dmin</I> and <I>dmax</I> settings are both used by the <I>scan</I> line search
as described above. For the <I>secant</I> line search, only the <I>dmin</I>
value is used to pick an initial point to begin the secant
approximation.
</P>
<P>The <I>lineiter</I> setting is used by the <I>secant</I> algorithm to limit its
iterations. The smaller the setting, the more inaccurate the line
search becomes. Nonlinear conjugate gradient is not thought to
require high-accuracy line searches in order to converge efficiently.
</P>
<P><B>Restrictions:</B> none
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "min_style.html">min_style</A>, <A HREF = "minimize.html">minimize</A>
</P>
<P><B>Default:</B>
</P>
<P>The option defaults are linestyle = secant, dmin = 1.0e-5, dmax = 0.1,
and lineiter = 10.
</P>
</HTML>