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<li>timer command</li>
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<div role="main" class="document" itemscope="itemscope" itemtype="http://schema.org/Article">
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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> or <em>timeout</em> or <em>every</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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<em>timeout</em> elapse = set walltime limit to <em>elapse</em>
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<em>every</em> Ncheck = perform timeout check every <em>Ncheck</em> steps
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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">timeout</span> <span class="mi">2</span><span class="p">:</span><span class="mi">00</span><span class="p">:</span><span class="mi">00</span> <span class="n">every</span> <span class="mi">100</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 at which LAMMPS performs its CPU timings.
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Multiple keywords can be specified with the <em>timer</em> command. For
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keywords that are mutually exclusive, the last one specified takes
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effect.</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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information for determining performance and load imbalance problems.
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This can be done at different levels of detail and accuracy. For more
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information about the timing output, see this <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>With the <em>timeout</em> keyword a walltime limit can be imposed that
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affects the <a class="reference internal" href="run.html"><span class="doc">run</span></a> and <a class="reference internal" href="minimize.html"><span class="doc">minimize</span></a> commands.
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This can be convenient when runs have to confirm to time limits,
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e.g. when running under a batch system and you want to maximize
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the utilization of the batch time slot, especially when the time
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per timestep varies and is thus difficult to predict how many
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steps a simulation can perform, or for difficult to converge
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minimizations. The timeout <em>elapse</em> value should be somewhat smaller
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than the time requested from the batch system, as there is usually
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some overhead to launch jobs, and it may be advisable to write
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out a restart after terminating a run due to a timeout.</p>
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<p>The timeout timer starts when the command is issued. When the time
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limit is reached, the run or energy minimization will exit on the
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next step or iteration that is a multiple of the <em>Ncheck</em> value
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which can be set with the <em>every</em> keyword. Default is checking
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every 10 steps. After the timer timeout has expired all subsequent
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run or minimize commands in the input script will be skipped.
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The remaining time or timer status can be accessed with the
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<a class="reference internal" href="thermo_style.html"><span class="doc">thermo</span></a> variable <em>timeremain</em>, which will be
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zero, if the timeout is inactive (default setting), it will be
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negative, if the timeout time is expired and positive if there
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is time remaining and in this case the value of the variable are
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the number of seconds remaining.</p>
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<p>When the <em>timeout</em> key word is used a second time, the timer is
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restarted with a new time limit. The timeout <em>elapse</em> value can
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be specified as <em>off</em> or <em>unlimited</em> to impose a no timeout condition
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(which is the default). The <em>elapse</em> setting can be specified as
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a single number for seconds, two numbers separated by a colon (MM:SS)
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for minutes and seconds, or as three numbers separated by colons for
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hours, minutes, and seconds (H:MM:SS).</p>
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<p>The <em>every</em> keyword sets how frequently during a run or energy
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minimization the wall clock will be checked. This check count applies
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to the outer iterations or time steps during minimizations or <a class="reference internal" href="run_style.html"><span class="doc">r-RESPA runs</span></a>, respectively. Checking for timeout too often,
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can slow a calculation down. Checking too infrequently can make the
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timeout measurement less accurate, with the run being stopped later
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than desired.</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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<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">timer</span> <span class="n">normal</span> <span class="n">nosync</span>
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<span class="n">timer</span> <span class="n">timeout</span> <span class="n">off</span>
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<span class="n">timer</span> <span class="n">every</span> <span class="mi">10</span>
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</pre></div>
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