<p>The NVT fix ramps the target temperature from 200.0 to 300.0 during a
run. If the run commands did not have the start/stop keywords (just
“run 1000”), then the temperature would ramp from 200.0 to 300.0
during the 1000 steps of each run. With the start/stop keywords, the
ramping takes place over the 10000 steps of all runs together.</p>
<p>The <em>pre</em> and <em>post</em> keywords can be used to streamline the setup,
clean-up, and associated output to the screen that happens before and
after a run. This can be useful if you wish to do many short runs in
succession (e.g. LAMMPS is being called as a library which is doing
other computations between successive short LAMMPS runs).</p>
<p>By default (pre and post = yes), LAMMPS creates neighbor lists,
computes forces, and imposes fix constraints before every run. And
after every run it gathers and prints timings statistics. If a run is
just a continuation of a previous run (i.e. no settings are changed),
the initial computation is not necessary; the old neighbor list is
still valid as are the forces. So if <em>pre</em> is specified as “no” then
the initial setup is skipped, except for printing thermodynamic info.
Note that if <em>pre</em> is set to “no” for the very 1st run LAMMPS
performs, then it is overridden, since the initial setup computations
must be done.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">If your input script changes the system between 2 runs, then the
initial setup must be performed to insure the change is recognized by
all parts of the code that are affected. Examples are adding a
<a class="reference internal" href="fix.html"><span class="doc">fix</span></a> or <a class="reference internal" href="dump.html"><span class="doc">dump</span></a> or <a class="reference internal" href="compute.html"><span class="doc">compute</span></a>, changing
a <a class="reference internal" href="neigh_modify.html"><span class="doc">neighbor</span></a> list parameter, or writing restart file
which can migrate atoms between processors. LAMMPS has no easy way to
check if this has happened, but it is an error to use the <em>pre no</em>
option in this case.</p>
</div>
<p>If <em>post</em> is specified as “no”, the full timing summary is skipped;
only a one-line summary timing is printed.</p>
<p>The <em>every</em> keyword provides a means of breaking a LAMMPS run into a
series of shorter runs. Optionally, one or more LAMMPS commands (c1,
c2, ..., cN) will be executed in between the short runs. If used, the
<em>every</em> keyword must be the last keyword, since it has a variable
number of arguments. Each of the trailing arguments is a single
LAMMPS command, and each command should be enclosed in quotes, so that
the entire command will be treated as a single argument. This will
also prevent any variables in the command from being evaluated until
it is executed multiple times during the run. Note that if a command
itself needs one of its arguments quoted (e.g. the <a class="reference internal" href="print.html"><span class="doc">print</span></a>
command), then you can use a combination of single and double quotes,
as in the example above or below.</p>
<p>The <em>every</em> keyword is a means to avoid listing a long series of runs
and interleaving commands in your input script. For example, a
<a class="reference internal" href="print.html"><span class="doc">print</span></a> command could be invoked or a <a class="reference internal" href="fix.html"><span class="doc">fix</span></a> could
be redefined, e.g. to reset a thermostat temperature. Or this could
be useful for invoking a command you have added to LAMMPS that wraps
some other code (e.g. as a library) to perform a computation
periodically during a long LAMMPS run. See <a class="reference internal" href="Section_modify.html"><span class="doc">this section</span></a> of the documentation for info about how
to add new commands to LAMMPS. See <a class="reference internal" href="Section_howto.html#howto-10"><span class="std std-ref">this section</span></a> of the documentation for ideas
about how to couple LAMMPS to other codes.</p>
<p>With the <em>every</em> option, N total steps are simulated, in shorter runs
of M steps each. After each M-length run, the specified commands are
invoked. If only a single command is specified as NULL, then no
Built with <a href="http://sphinx-doc.org/">Sphinx</a> using a <a href="https://github.com/snide/sphinx_rtd_theme">theme</a> provided by <a href="https://readthedocs.org">Read the Docs</a>.