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