2006-09-22 00:22:34 +08:00
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<HTML>
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2010-05-07 23:11:21 +08:00
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<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Page</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
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2006-09-22 00:22:34 +08:00
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</CENTER>
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<HR>
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<H3>min_style 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_style style
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</PRE>
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2010-06-04 08:19:53 +08:00
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<UL><LI>style = <I>cg</I> or <I>hftn</I> or <I>sd</I>
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2006-09-22 00:22:34 +08:00
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>min_style cg
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min_style hftn
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2006-09-22 00:22:34 +08:00
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Choose a minimization algorithm to use when a <A HREF = "minimize.html">minimize</A>
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command is performed.
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</P>
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2010-06-04 08:19:53 +08:00
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<P>Style <I>cg</I> is the Polak-Ribiere version of the conjugate gradient (CG)
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algorithm. At each iteration the force gradient is combined with the
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previous iteration information to compute a new search direction
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perpendicular (conjugate) to the previous search direction. The PR
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variant affects how the direction is chosen and how the CG method is
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restarted when it ceases to make progress. The PR variant is thought
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to be the most effective CG choice.
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2006-09-22 00:22:34 +08:00
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</P>
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2009-09-29 22:10:23 +08:00
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<P>Style <I>hftn</I> is a Hessian-free truncated Newton algorithm. At each
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iteration a quadratic model of the energy potential is solved by a
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conjugate gradient inner iteration. The Hessian (second derivatives)
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of the energy is not formed directly, but approximated in each
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conjugate search direction by a finite difference directional
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derivative. When close to an energy minimum, the algorithm behaves
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like a Newton method and exhibits a quadratic convergence rate to high
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accuracy. In most cases the behavior of <I>hftn</I> is similar to <I>cg</I>,
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2009-09-29 22:10:23 +08:00
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but it offers another minimizer alternative if <I>cg</I> seems to perform
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poorly. This style is not affected by the
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<A HREF = "min_modify.html">min_modify</A> command.
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2009-09-29 22:10:23 +08:00
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</P>
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2006-09-22 00:22:34 +08:00
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<P>Style <I>sd</I> is a steepest descent algorithm. At each iteration, the
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2008-04-15 05:37:10 +08:00
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search direction is set to the downhill direction corresponding to the
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2010-06-04 08:19:53 +08:00
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force vector (negative gradient of energy). Typically, steepest
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descent will not converge as quickly as CG, but may be more robust in
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some situations.
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2006-09-22 00:22:34 +08:00
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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_modify.html">min_modify</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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<PRE>min_style cg
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</PRE>
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</HTML>
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