forked from lijiext/lammps
68 lines
2.1 KiB
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68 lines
2.1 KiB
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<HTML>
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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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<H3>newton command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>newton flag
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newton flag1 flag2
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</PRE>
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<UL><LI>flag = <I>on</I> or <I>off</I> for both pairwise and bonded interactions
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<LI>flag1 = <I>on</I> or <I>off</I> for pairwise interactions
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<LI>flag2 = <I>on</I> or <I>off</I> for bonded interactions
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>newton off
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newton on off
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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 turns Newton's 3rd law <I>on</I> or <I>off</I> for pairwise and
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bonded interactions. For most problems, setting Newton's 3rd law to
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<I>on</I> means a modest savings in computation at the cost of two times
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more communication. Whether this is faster depends on problem size,
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force cutoff lengths, a machine's compute/communication ratio, and how
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many processors are being used.
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</P>
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<P>Setting the pairwise newton flag to <I>off</I> means that if two
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interacting atoms are on different processors, both processors compute
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their interaction and the resulting force information is not
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communicated. Similarly, for bonded interactions, newton <I>off</I> means
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that if a bond, angle, dihedral, or improper interaction contains
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atoms on 2 or more processors, the interaction is computed by each
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processor.
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</P>
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<P>LAMMPS should produce the same answers for any newton flag settings,
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except for round-off issues.
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</P>
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<P>With <A HREF = "run_style.html">run_style</A> <I>respa</I> and only bonded interactions
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(bond, angle, etc) computed in the innermost timestep, it may be
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faster to turn newton <I>off</I> for bonded interactions, to avoid extra
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communication in the innermost loop.
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</P>
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<P><B>Restrictions:</B>
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</P>
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<P>The newton bond setting cannot be changed after the simulation box is
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defined by a <A HREF = "read_data.html">read_data</A> or
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<A HREF = "create_box.html">create_box</A> command.
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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 = "run_style.html">run_style</A> respa
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</P>
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<P><B>Default:</B>
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</P>
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<PRE>newton on
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</PRE>
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</HTML>
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