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<li class="toctree-l1"><a class="reference internal" href="Section_intro.html">1. Introduction</a></li>
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<li class="toctree-l1"><a class="reference internal" href="Section_accelerate.html">5. Accelerating LAMMPS performance</a></li>
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<li>timer command</li>
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<div class="section" id="timer-command">
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<span id="index-0"></span><h1>timer command</h1>
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<div class="section" id="syntax">
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<h2>Syntax</h2>
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<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">timer</span> <span class="n">args</span>
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</pre></div>
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</div>
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<ul class="simple">
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<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>
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</ul>
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<pre class="literal-block">
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<em>off</em> = do not collect or print any timing information
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<em>loop</em> = collect only the total time for the simulation loop
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<em>normal</em> = collect timer information broken down by sections (default)
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<em>full</em> = like <em>normal</em> but also include CPU and thread utilzation
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<em>sync</em> = explicitly synchronize MPI tasks between sections
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<em>nosync</em> = do not synchronize MPI tasks between sections (default)
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</pre>
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</div>
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<div class="section" id="examples">
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<h2>Examples</h2>
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<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">timer</span> <span class="n">full</span> <span class="n">sync</span>
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<span class="n">timer</span> <span class="n">loop</span>
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</pre></div>
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</div>
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</div>
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<div class="section" id="description">
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<h2>Description</h2>
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<p>Select the level of detail LAMMPS performs its CPU timings.</p>
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<p>During a simulation run LAMMPS collects information about how much
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time is spent in different sections of the code and thus can provide
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valuable information for determining performance and load imbalance
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problems. This can be done at different levels of detail and
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accuracy. For more information about the timing output, see this
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<a class="reference internal" href="Section_start.html#start-8"><span class="std std-ref">discussion of screen output</span></a>.</p>
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<p>The <em>off</em> setting will turn all time measurements off. The <em>loop</em>
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setting will only measure the total time for a run and not collect any
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detailed per section information. With the <em>normal</em> setting, timing
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information for portions of the timestep (pairwise calculations,
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neighbor list construction, output, etc) are collected as well as
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information about load imbalances for those sections across
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procsessors. The <em>full</em> setting adds information about CPU
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utilization and thread utilization, when multi-threading is enabled.</p>
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<p>With the <em>sync</em> setting, all MPI tasks are synchronized at each timer
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call which meaures load imbalance more accuractly, though it can also
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slow down the simulation. Using the <em>nosync</em> setting (which is the
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default) turns off this synchronization.</p>
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<p>Multiple keywords can be specified. For keywords that are mutually
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exclusive, the last one specified takes effect.</p>
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<div class="admonition note">
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<p class="first admonition-title">Note</p>
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<p class="last">Using the <em>full</em> and <em>sync</em> options provides the most detailed
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and accurate timing information, but can also have a negative
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performance impact due to the overhead of the many required system
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calls. It is thus recommended to use these settings only when testing
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tests to identify performance bottlenecks. For calculations with few
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atoms or a very large number of processors, even the <em>normal</em> setting
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can have a measurable negative performance impact. In those cases you
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can just use the <em>loop</em> or <em>off</em> setting.</p>
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</div>
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</div>
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<div class="section" id="restrictions">
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<h2>Restrictions</h2>
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<blockquote>
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<div>none</div></blockquote>
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</div>
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<div class="section" id="related-commands">
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<h2>Related commands</h2>
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<p><a class="reference internal" href="run.html"><span class="doc">run post no</span></a>, <a class="reference internal" href="kspace_modify.html"><span class="doc">kspace_modify fftbench</span></a></p>
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</div>
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<div class="section" id="default">
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<h2>Default</h2>
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<p>timer normal nosync</p>
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