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Sun, Dec 29, 18:27
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Tue, Dec 31, 18:27 (2 d)
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rLAMMPS lammps
newton.html
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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>
newton command
</H3>
<P><B>
Syntax:
</B>
</P>
<PRE>
newton flag
newton flag1 flag2
</PRE>
<UL><LI>
flag =
<I>
on
</I>
or
<I>
off
</I>
for both pairwise and bonded interactions
<LI>
flag1 =
<I>
on
</I>
or
<I>
off
</I>
for pairwise interactions
<LI>
flag2 =
<I>
on
</I>
or
<I>
off
</I>
for bonded interactions
</UL>
<P><B>
Examples:
</B>
</P>
<PRE>
newton off
newton on off
</PRE>
<P><B>
Description:
</B>
</P>
<P>
This command turns Newton's 3rd law
<I>
on
</I>
or
<I>
off
</I>
for pairwise and
bonded interactions. For most problems, setting Newton's 3rd law to
<I>
on
</I>
means a modest savings in computation at the cost of two times
more communication. Whether this is faster depends on problem size,
force cutoff lengths, a machine's compute/communication ratio, and how
many processors are being used.
</P>
<P>
Setting the pairwise newton flag to
<I>
off
</I>
means that if two
interacting atoms are on different processors, both processors compute
their interaction and the resulting force information is not
communicated. Similarly, for bonded interactions, newton
<I>
off
</I>
means
that if a bond, angle, dihedral, or improper interaction contains
atoms on 2 or more processors, the interaction is computed by each
processor.
</P>
<P>
LAMMPS should produce the same answers for any newton flag settings,
except for round-off issues.
</P>
<P>
With
<A
HREF =
"run_style.html"
>
run_style
</A>
<I>
respa
</I>
and only bonded interactions
(bond, angle, etc) computed in the innermost timestep, it may be
faster to turn newton
<I>
off
</I>
for bonded interactions, to avoid extra
communication in the innermost loop.
</P>
<P><B>
Restrictions:
</B>
</P>
<P>
The newton bond setting cannot be changed after the simulation box is
defined by a
<A
HREF =
"read_data.html"
>
read_data
</A>
or
<A
HREF =
"create_box.html"
>
create_box
</A>
command.
</P>
<P><B>
Related commands:
</B>
</P>
<P><A
HREF =
"run_style.html"
>
run_style
</A>
respa
</P>
<P><B>
Default:
</B>
</P>
<PRE>
newton on
</PRE>
</HTML>
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