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<title>timestep command &mdash; LAMMPS 15 May 2015 version documentation</title>
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<li class="toctree-l1"><a class="reference internal" href="Section_intro.html">1. Introduction</a></li>
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<div class="section" id="timestep-command">
<span id="index-0"></span><h1>timestep command<a class="headerlink" href="#timestep-command" title="Permalink to this headline">¶</a></h1>
<div class="section" id="syntax">
<h2>Syntax<a class="headerlink" href="#syntax" title="Permalink to this headline">¶</a></h2>
<div class="highlight-python"><div class="highlight"><pre>timers args
</pre></div>
</div>
<ul class="simple">
<li><em>args</em> = one or more of <em>off</em> or <em>loop</em> or <em>normal</em> or <em>full</em> or <em>sync</em> or <em>nosync</em></li>
</ul>
<pre class="literal-block">
<em>off</em> = do not collect and print timing information
<em>loop</em> = collect only the total time for the simulation loop
<em>normal</em> = collect timer information broken down in sections (default)
<em>full</em> = like <em>normal</em> but also include CPU and thread utilzation
<em>sync</em> = explicitly synchronize MPI tasks between sections
<em>nosync</em> = do not synchronize MPI tasks when collecting timer info (default)
</pre>
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<div class="section" id="examples">
<h2>Examples<a class="headerlink" href="#examples" title="Permalink to this headline">¶</a></h2>
<div class="highlight-python"><div class="highlight"><pre>timers full sync
timers loop
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2>
<p>Select to which level of detail LAMMPS is performing internal profiling.</p>
<p>During regular runs LAMMPS will collect information about how much time is
spent in different sections of the code and thus can provide valuable
information for determining performance and load imbalance problems. This
can be done at different levels of detail and accuracy. For more
information about the timing output, please have a look at the <a class="reference internal" href="Section_start.html#start-8"><span>discussion of screen output</span></a>.</p>
<p>The <em>off</em> setting will turn all time measurements off. The <em>loop</em> setting
will only measure the total time of run loop and not collect any detailed
per section information. With the <em>normal</em> setting, timing information for
individual sections of the code are collected and also information about
load imbalances inside those sections presented. The <em>full</em> setting adds
information about CPU utilization and thread utilization, when multi-threading
is enabled.</p>
<p>With the <em>sync</em> setting, all MPI tasks are synchronized at each timer call
and thus allowing to study load imbalance more accuractly, but this usually
has some performance impact. Using the <em>nosync</em> setting this can be turned
off (which is the default).</p>
<p>Multiple keywords can be provided and for keywords that are mutually
exclusive, the last one in that group is taking effect.</p>
<div class="admonition warning">
<p class="first admonition-title">Warning</p>
<p class="last">Using the <em>full</em> and <em>sync</em> options provides the most
detailed and accurate timing information, but also can have a significant
negative performance impact due to the overhead of the many required system
calls. It is thus recommended to use these settings only when making tests
to identify the performance. For calculations with few atoms or a very
large number of performance, even using the <em>normal</em> setting can have
a measurable performance impact. It is recommended in those cases to use
the <em>loop</em> or <em>off</em> setting.</p>
</div>
</div>
<div class="section" id="restrictions">
<h2>Restrictions<a class="headerlink" href="#restrictions" title="Permalink to this headline">¶</a></h2>
<blockquote>
<div>none</div></blockquote>
</div>
<div class="section" id="related-commands">
<h2>Related commands<a class="headerlink" href="#related-commands" title="Permalink to this headline">¶</a></h2>
<p><a class="reference internal" href="run.html"><em>run post no</em></a>, <a class="reference internal" href="kspace_modify.html"><em>kspace_modify fftbench</em></a></p>
</div>
<div class="section" id="default">
<h2>Default<a class="headerlink" href="#default" title="Permalink to this headline">¶</a></h2>
<p>timers normal nosync</p>
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