forked from lijiext/lammps
158 lines
6.1 KiB
HTML
158 lines
6.1 KiB
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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</CENTER>
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<HR>
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<H3>run command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>run N keyword values ...
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</PRE>
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<UL><LI>N = # of timesteps
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<LI>zero or more keyword/value pairs may be appended
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<LI>keyword = <I>upto</I> or <I>start</I> or <I>stop</I> or <I>pre</I> or <I>post</I> or <I>every</I>
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<PRE> <I>upto</I> value = none
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<I>start</I> value = N1
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N1 = timestep at which 1st run started
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<I>stop</I> value = N2
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N2 = timestep at which last run will end
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<I>pre</I> value = <I>no</I> or <I>yes</I>
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<I>post</I> value = <I>no</I> or <I>yes</I>
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<I>every</I> values = M command
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M = break the run into M-timestep segments and invoke command between them
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command = a single LAMMPS command (enclosed in double quotes if multiple words)
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NULL means no command will be invoked
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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>run 10000
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run 1000000 upto
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run 100 start 0 stop 1000
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run 1000 pre no post yes
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run 100000 start 0 stop 1000000 every 1000 "print Protein Rg = $r"
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run 100000 every 1000 NULL
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Run or continue dynamics for a specified number of timesteps.
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</P>
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<P>When the <A HREF = "doc/run_style.html">run style</A> is <I>respa</I>, N refers to outer
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loop (largest) timesteps.
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</P>
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<P>A value of N = 0 is acceptable; only the thermodynamics of the system
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are computed and printed without taking a timestep.
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</P>
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<P>The <I>upto</I> keyword means to perform a run starting at the current
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timestep up to the specified timestep. E.g. if the current timestep
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is 10,000 and "run 100000 upto" is used, then an additional 90,000
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timesteps will be run. This can be useful for very long runs on a
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machine that allocates chunks of time and terminate your job when time
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is exceeded. If you need to restart your script multiple times
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(reading in the last restart file), you can keep restarting your
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script with the same run command until the simulation finally
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completes.
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</P>
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<P>The <I>start</I> or <I>stop</I> keywords can be used if multiple runs are being
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performed and you want a <A HREF = "fix.html">fix</A> command that ramps some value
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(e.g. a temperature) over time to do its ramping across the entire set
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of runs and not just a single run. Fixes in this category include
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<A HREF = "fix_nvt.html">fix nvt</A>, <A HREF = "fix_npt.html">fix npt</A>, <A HREF = "fix_langevin.html">fix
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langevin</A>, <A HREF = "fix_temp_rescale.html">fix temp/rescale</A>,
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<A HREF = "fix_volume_rescale.html">fix volume/rescale</A>, and <A HREF = "fix_indent.html">fix
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indent</A>. The <A HREF = "pair_style.html">pair_style soft</A>
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potential also ramps its coefficients in a similar way.
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</P>
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<P>For example, consider this fix followed by 10 run commands:
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</P>
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<PRE>fix 1 all nvt 200.0 300.0 1.0
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run 1000 start 0 stop 10000
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run 1000 start 0 stop 10000
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...
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run 1000 start 0 stop 10000
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</PRE>
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<P>The NVT fix ramps the target temperature from 200.0 to 300.0 during a
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run. If the run commands did not have the start/stop keywords (just
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"run 1000"), then the temperature would ramp from 200.0 to 300.0
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during the 1000 steps of each run. With the start/stop keywords, the
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ramping takes place over the 10000 steps of all runs together.
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</P>
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<P>The <I>pre</I> and <I>post</I> keywords can be used to streamline the setup,
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clean-up, and associated output to the screen that happens before and
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after a run. This can be useful if you wish to do many short runs in
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succession (e.g. LAMMPS is being called as a library which is doing
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other computations between successive short LAMMPS runs).
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</P>
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<P>By default (pre and post = yes), LAMMPS creates neighbor lists,
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computes forces, and imposes fix constraints before every run. And
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after every run it gathers and prints timings statistics. If a run is
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just a continuation of a previous run (and no parameters have
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changed), the initial computation is not necessary; the old neighbor
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list is still valid as are the forces. So if <I>pre</I> is specified as
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"no" then the initial setup is skipped, except for printing
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thermodynamic info. Likewise, if <I>post</I> is specified as "no", the
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full timing summary is skipped; only a one-line summary timing is
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printed. Note that if <I>pre</I> is set to "no" for the 1st run LAMMPS
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performs, then it is overridden, since the initial setup computations
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must be done.
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</P>
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<P>The <I>every</I> option provides a means of interleaving LAMMPS runs with a
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command. This can be a short-hand abbreviation to avoid listing a
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long series of runs in your input script. Or it can be useful for
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invoking a command that wraps some other code (e.g. as a library) to
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perform a computation periodically during a long LAMMPS run. See
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<A HREF = "Section_howto.html#4_10">this section</A> of the documentation for ideas
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about how to couple LAMMPS to other codes.
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</P>
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<P>N total steps are simulated, in shorter runs of M steps each. After
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each M-length run, the command is invoked. If the command is
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specified as NULL, no command is invoked. Thus these lines:
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</P>
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<PRE>variable q equal x<B>100</B>
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run 6000 every 2000 "print Coord = $q"
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</PRE>
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<P>are the equivalent of:
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</P>
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<PRE>variable q equal x[100]
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run 2000
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print Coord = $q
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run 2000
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print Coord = $q
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run 2000
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print Coord = $q
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</PRE>
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<P>which does 3 runs of 2000 steps and prints the x-coordinate of a
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particular atom between runs. Note that the command can contain
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<A HREF = "variable.html">variables</A> of style <I>equal</I> which will be evaluated
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each time the command is invoked.
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</P>
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<P>If the <I>pre</I> and <I>post</I> options are set to "no" when <I>every</I> is used,
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then the 1st run will do the full setup and the last run will print
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the full timing summary, but these operations will be skipped for
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intermediate runs.
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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 = "minimize.html">minimize</A>, <A HREF = "run_style.html">run_style</A>,
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<A HREF = "temper.html">temper</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 start = the current timestep, stop = current
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timestep + N, pre = yes, and post = yes.
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</P>
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</HTML>
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