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<div class="section" id="fix-ave-time-command">
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<span id="index-0"></span><h1>fix ave/time 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">fix</span> <span class="n">ID</span> <span class="n">group</span><span class="o">-</span><span class="n">ID</span> <span class="n">ave</span><span class="o">/</span><span class="n">time</span> <span class="n">Nevery</span> <span class="n">Nrepeat</span> <span class="n">Nfreq</span> <span class="n">value1</span> <span class="n">value2</span> <span class="o">...</span> <span class="n">keyword</span> <span class="n">args</span> <span class="o">...</span>
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</pre></div>
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</div>
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<ul class="simple">
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<li>ID, group-ID are documented in <a class="reference internal" href="fix.html"><span class="doc">fix</span></a> command</li>
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<li>ave/time = style name of this fix command</li>
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<li>Nevery = use input values every this many timesteps</li>
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<li>Nrepeat = # of times to use input values for calculating averages</li>
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<li>Nfreq = calculate averages every this many timesteps</li>
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<li>one or more input values can be listed</li>
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<li>value = c_ID, c_ID[N], f_ID, f_ID[N], v_name</li>
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</ul>
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<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">c_ID</span> <span class="o">=</span> <span class="k">global</span> <span class="n">scalar</span><span class="p">,</span> <span class="n">vector</span><span class="p">,</span> <span class="ow">or</span> <span class="n">array</span> <span class="n">calculated</span> <span class="n">by</span> <span class="n">a</span> <span class="n">compute</span> <span class="k">with</span> <span class="n">ID</span>
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<span class="n">c_ID</span><span class="p">[</span><span class="n">I</span><span class="p">]</span> <span class="o">=</span> <span class="n">Ith</span> <span class="n">component</span> <span class="n">of</span> <span class="k">global</span> <span class="n">vector</span> <span class="ow">or</span> <span class="n">Ith</span> <span class="n">column</span> <span class="n">of</span> <span class="k">global</span> <span class="n">array</span> <span class="n">calculated</span> <span class="n">by</span> <span class="n">a</span> <span class="n">compute</span> <span class="k">with</span> <span class="n">ID</span>
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<span class="n">f_ID</span> <span class="o">=</span> <span class="k">global</span> <span class="n">scalar</span><span class="p">,</span> <span class="n">vector</span><span class="p">,</span> <span class="ow">or</span> <span class="n">array</span> <span class="n">calculated</span> <span class="n">by</span> <span class="n">a</span> <span class="n">fix</span> <span class="k">with</span> <span class="n">ID</span>
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<span class="n">f_ID</span><span class="p">[</span><span class="n">I</span><span class="p">]</span> <span class="o">=</span> <span class="n">Ith</span> <span class="n">component</span> <span class="n">of</span> <span class="k">global</span> <span class="n">vector</span> <span class="ow">or</span> <span class="n">Ith</span> <span class="n">column</span> <span class="n">of</span> <span class="k">global</span> <span class="n">array</span> <span class="n">calculated</span> <span class="n">by</span> <span class="n">a</span> <span class="n">fix</span> <span class="k">with</span> <span class="n">ID</span>
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<span class="n">v_name</span> <span class="o">=</span> <span class="n">value</span><span class="p">(</span><span class="n">s</span><span class="p">)</span> <span class="n">calculated</span> <span class="n">by</span> <span class="n">an</span> <span class="n">equal</span><span class="o">-</span><span class="n">style</span> <span class="ow">or</span> <span class="n">vector</span><span class="o">-</span><span class="n">style</span> <span class="n">variable</span> <span class="k">with</span> <span class="n">name</span>
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<span class="n">v_name</span><span class="p">[</span><span class="n">I</span><span class="p">]</span> <span class="o">=</span> <span class="n">value</span> <span class="n">calculated</span> <span class="n">by</span> <span class="n">a</span> <span class="n">vector</span><span class="o">-</span><span class="n">style</span> <span class="n">variable</span> <span class="k">with</span> <span class="n">name</span>
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</pre></div>
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</div>
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<ul class="simple">
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<li>zero or more keyword/arg pairs may be appended</li>
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<li>keyword = <em>mode</em> or <em>file</em> or <em>ave</em> or <em>start</em> or <em>off</em> or <em>overwrite</em> or <em>title1</em> or <em>title2</em> or <em>title3</em></li>
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</ul>
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<pre class="literal-block">
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<em>mode</em> arg = <em>scalar</em> or <em>vector</em>
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scalar = all input values are global scalars
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vector = all input values are global vectors or global arrays
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<em>ave</em> args = <em>one</em> or <em>running</em> or <em>window M</em>
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one = output a new average value every Nfreq steps
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running = output cummulative average of all previous Nfreq steps
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window M = output average of M most recent Nfreq steps
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<em>start</em> args = Nstart
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Nstart = start averaging on this timestep
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<em>off</em> arg = M = do not average this value
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M = value # from 1 to Nvalues
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<em>file</em> arg = filename
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filename = name of file to output time averages to
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<em>overwrite</em> arg = none = overwrite output file with only latest output
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<em>format</em> arg = string
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string = C-style format string
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<em>title1</em> arg = string
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string = text to print as 1st line of output file
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<em>title2</em> arg = string
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string = text to print as 2nd line of output file
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<em>title3</em> arg = string
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string = text to print as 3rd line of output file, only for vector mode
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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">fix</span> <span class="mi">1</span> <span class="nb">all</span> <span class="n">ave</span><span class="o">/</span><span class="n">time</span> <span class="mi">100</span> <span class="mi">5</span> <span class="mi">1000</span> <span class="n">c_myTemp</span> <span class="n">c_thermo_temp</span> <span class="n">file</span> <span class="n">temp</span><span class="o">.</span><span class="n">profile</span>
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<span class="n">fix</span> <span class="mi">1</span> <span class="nb">all</span> <span class="n">ave</span><span class="o">/</span><span class="n">time</span> <span class="mi">100</span> <span class="mi">5</span> <span class="mi">1000</span> <span class="n">c_thermo_press</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span> <span class="n">ave</span> <span class="n">window</span> <span class="mi">20</span> <span class="o">&</span>
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<span class="n">title1</span> <span class="s2">"My output values"</span>
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<span class="n">fix</span> <span class="mi">1</span> <span class="nb">all</span> <span class="n">ave</span><span class="o">/</span><span class="n">time</span> <span class="mi">1</span> <span class="mi">100</span> <span class="mi">1000</span> <span class="n">f_indent</span> <span class="n">f_indent</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="n">file</span> <span class="n">temp</span><span class="o">.</span><span class="n">indent</span> <span class="n">off</span> <span class="mi">1</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>Use one or more global values as inputs every few timesteps, and
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average them over longer timescales. The resulting averages can be
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used by other <a class="reference internal" href="Section_howto.html#howto-15"><span class="std std-ref">output commands</span></a> such as
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<a class="reference internal" href="thermo_style.html"><span class="doc">thermo_style custom</span></a>, and can also be written to a
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file. Note that if no time averaging is done, this command can be
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used as a convenient way to simply output one or more global values to
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a file.</p>
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<p>The group specified with this command is ignored. However, note that
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specified values may represent calculations performed by computes and
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fixes which store their own “group” definitions.</p>
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<p>Each listed value can be the result of a <a class="reference internal" href="compute.html"><span class="doc">compute</span></a> or
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<a class="reference internal" href="fix.html"><span class="doc">fix</span></a> or the evaluation of an equal-style or vector-style
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<a class="reference internal" href="variable.html"><span class="doc">variable</span></a>. In each case, the compute, fix, or variable
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must produce a global quantity, not a per-atom or local quantity. If
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you wish to spatial- or time-average or histogram per-atom quantities
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from a compute, fix, or variable, then see the <a class="reference internal" href="fix_ave_chunk.html"><span class="doc">fix ave/chunk</span></a>, <a class="reference internal" href="fix_ave_atom.html"><span class="doc">fix ave/atom</span></a>,
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or <a class="reference internal" href="fix_ave_histo.html"><span class="doc">fix ave/histo</span></a> commands. If you wish to sum a
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per-atom quantity into a single global quantity, see the <a class="reference internal" href="compute_reduce.html"><span class="doc">compute reduce</span></a> command.</p>
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<p><a class="reference internal" href="compute.html"><span class="doc">Computes</span></a> that produce global quantities are those which
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do not have the word <em>atom</em> in their style name. Only a few
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<a class="reference internal" href="fix.html"><span class="doc">fixes</span></a> produce global quantities. See the doc pages for
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individual fixes for info on which ones produce such values.
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<a class="reference internal" href="variable.html"><span class="doc">Variables</span></a> of style <em>equal</em> and <em>vector</em> are the only
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ones that can be used with this fix. Variables of style <em>atom</em> cannot
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be used, since they produce per-atom values.</p>
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<p>The input values must either be all scalars or all vectors (or
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arrays), depending on the setting of the <em>mode</em> keyword. In both
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cases, the averaging is performed independently on each input value.
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I.e. each input scalar is averaged independently and each element of
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each input vector (or array) is averaged independently.</p>
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<p>If <em>mode</em> = vector, then the input values may either be vectors or
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arrays and all must be the same “length”, which is the length of the
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vector or number of rows in the array. If a global array is listed,
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then it is the same as if the individual columns of the array had been
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listed one by one. E.g. these 2 fix ave/time commands are equivalent,
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since the <a class="reference internal" href="compute_rdf.html"><span class="doc">compute rdf</span></a> command creates, in this
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case, a global array with 3 columns, each of length 50:</p>
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<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">compute</span> <span class="n">myRDF</span> <span class="nb">all</span> <span class="n">rdf</span> <span class="mi">50</span> <span class="mi">1</span> <span class="mi">2</span>
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<span class="n">fix</span> <span class="mi">1</span> <span class="nb">all</span> <span class="n">ave</span><span class="o">/</span><span class="n">time</span> <span class="mi">100</span> <span class="mi">1</span> <span class="mi">100</span> <span class="n">c_myRDF</span> <span class="n">file</span> <span class="n">tmp1</span><span class="o">.</span><span class="n">rdf</span> <span class="n">mode</span> <span class="n">vector</span>
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<span class="n">fix</span> <span class="mi">2</span> <span class="nb">all</span> <span class="n">ave</span><span class="o">/</span><span class="n">time</span> <span class="mi">100</span> <span class="mi">1</span> <span class="mi">100</span> <span class="n">c_myRDF</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="n">c_myRDF</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span> <span class="n">c_myRDF</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span> <span class="n">file</span> <span class="n">tmp2</span><span class="o">.</span><span class="n">rdf</span> <span class="n">mode</span> <span class="n">vector</span>
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</pre></div>
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</div>
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<hr class="docutils" />
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<p>The <em>Nevery</em>, <em>Nrepeat</em>, and <em>Nfreq</em> arguments specify on what
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timesteps the input values will be used in order to contribute to the
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average. The final averaged quantities are generated on timesteps
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that are a mlutiple of <em>Nfreq</em>. The average is over <em>Nrepeat</em>
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quantities, computed in the preceding portion of the simulation every
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<em>Nevery</em> timesteps. <em>Nfreq</em> must be a multiple of <em>Nevery</em> and
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<em>Nevery</em> must be non-zero even if <em>Nrepeat</em> is 1. Also, the timesteps
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contributing to the average value cannot overlap,
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i.e. Nrepeat*Nevery can not exceed Nfreq.</p>
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<p>For example, if Nevery=2, Nrepeat=6, and Nfreq=100, then values on
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timesteps 90,92,94,96,98,100 will be used to compute the final average
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on timestep 100. Similarly for timesteps 190,192,194,196,198,200 on
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timestep 200, etc. If Nrepeat=1 and Nfreq = 100, then no time
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averaging is done; values are simply generated on timesteps
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100,200,etc.</p>
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<hr class="docutils" />
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<p>If a value begins with “<a href="#id1"><span class="problematic" id="id2">c_</span></a>”, a compute ID must follow which has been
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previously defined in the input script. If <em>mode</em> = scalar, then if
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no bracketed term is appended, the global scalar calculated by the
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compute is used. If a bracketed term is appended, the Ith element of
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the global vector calculated by the compute is used. If <em>mode</em> =
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vector, then if no bracketed term is appended, the global vector
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calculated by the compute is used. Or if the compute calculates an
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array, all of the columns of the global array are used as if they had
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been specified as individual vectors (see description above). If a
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bracketed term is appended, the Ith column of the global array
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calculated by the compute is used.</p>
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<p>Note that there is a <a class="reference internal" href="compute_reduce.html"><span class="doc">compute reduce</span></a> command
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which can sum per-atom quantities into a global scalar or vector which
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can thus be accessed by fix ave/time. Or it can be a compute defined
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not in your input script, but by <a class="reference internal" href="thermo_style.html"><span class="doc">thermodynamic output</span></a> or other fixes such as <a class="reference internal" href="fix_nh.html"><span class="doc">fix nvt</span></a> or <a class="reference internal" href="fix_temp_rescale.html"><span class="doc">fix temp/rescale</span></a>. See
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the doc pages for these commands which give the IDs of these computes.
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Users can also write code for their own compute styles and <a class="reference internal" href="Section_modify.html"><span class="doc">add them to LAMMPS</span></a>.</p>
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<p>If a value begins with “<a href="#id3"><span class="problematic" id="id4">f_</span></a>”, a fix ID must follow which has been
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previously defined in the input script. If <em>mode</em> = scalar, then if
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no bracketed term is appended, the global scalar calculated by the fix
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is used. If a bracketed term is appended, the Ith element of the
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global vector calculated by the fix is used. If <em>mode</em> = vector, then
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if no bracketed term is appended, the global vector calculated by the
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fix is used. Or if the fix calculates an array, all of the columns of
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the global array are used as if they had been specified as individual
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vectors (see description above). If a bracketed term is appended, the
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Ith column of the global array calculated by the fix is used.</p>
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<p>Note that some fixes only produce their values on certain timesteps,
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|
which must be compatible with <em>Nevery</em>, else an error will result.
|
|
Users can also write code for their own fix styles and <a class="reference internal" href="Section_modify.html"><span class="doc">add them to LAMMPS</span></a>.</p>
|
|
<p>If a value begins with “<a href="#id5"><span class="problematic" id="id6">v_</span></a>”, a variable name must follow which has
|
|
been previously defined in the input script. If <em>mode</em> = scalar, then
|
|
only equal-style or vector-style variables can be used, which both
|
|
produce global values. In this mode, a vector-style variable requires
|
|
a bracketed term to specify the Ith element of the vector calculated
|
|
by the variable. If <em>mode</em> = vector, then only a vector-style
|
|
variable can be used, without a bracketed term. See the
|
|
<a class="reference internal" href="variable.html"><span class="doc">variable</span></a> command for details.</p>
|
|
<p>Note that variables of style <em>equal</em> and <em>vector</em> define a formula
|
|
which can reference individual atom properties or thermodynamic
|
|
keywords, or they can invoke other computes, fixes, or variables when
|
|
they are evaluated, so this is a very general means of specifying
|
|
quantities to time average.</p>
|
|
<hr class="docutils" />
|
|
<p>Additional optional keywords also affect the operation of this fix.</p>
|
|
<p>If the <em>mode</em> keyword is set to <em>scalar</em>, then all input values must
|
|
be global scalars, or elements of global vectors. If the <em>mode</em>
|
|
keyword is set to <em>vector</em>, then all input values must be global
|
|
vectors, or columns of global arrays. They can also be global arrays,
|
|
which are converted into a series of global vectors (one per column),
|
|
as explained above.</p>
|
|
<p>The <em>ave</em> keyword determines how the values produced every <em>Nfreq</em>
|
|
steps are averaged with values produced on previous steps that were
|
|
multiples of <em>Nfreq</em>, before they are accessed by another output
|
|
command or written to a file.</p>
|
|
<p>If the <em>ave</em> setting is <em>one</em>, then the values produced on timesteps
|
|
that are multiples of <em>Nfreq</em> are independent of each other; they are
|
|
output as-is without further averaging.</p>
|
|
<p>If the <em>ave</em> setting is <em>running</em>, then the values produced on
|
|
timesteps that are multiples of <em>Nfreq</em> are summed and averaged in a
|
|
cummulative sense before being output. Each output value is thus the
|
|
average of the value produced on that timestep with all preceding
|
|
values. This running average begins when the fix is defined; it can
|
|
only be restarted by deleting the fix via the <a class="reference internal" href="unfix.html"><span class="doc">unfix</span></a>
|
|
command, or by re-defining the fix by re-specifying it.</p>
|
|
<p>If the <em>ave</em> setting is <em>window</em>, then the values produced on
|
|
timesteps that are multiples of <em>Nfreq</em> are summed and averaged within
|
|
a moving “window” of time, so that the last M values are used to
|
|
produce the output. E.g. if M = 3 and Nfreq = 1000, then the output
|
|
on step 10000 will be the average of the individual values on steps
|
|
8000,9000,10000. Outputs on early steps will average over less than M
|
|
values if they are not available.</p>
|
|
<p>The <em>start</em> keyword specifies what timestep averaging will begin on.
|
|
The default is step 0. Often input values can be 0.0 at time 0, so
|
|
setting <em>start</em> to a larger value can avoid including a 0.0 in a
|
|
running or windowed average.</p>
|
|
<p>The <em>off</em> keyword can be used to flag any of the input values. If a
|
|
value is flagged, it will not be time averaged. Instead the most
|
|
recent input value will always be stored and output. This is useful
|
|
if one of more of the inputs produced by a compute or fix or variable
|
|
are effectively constant or are simply current values. E.g. they are
|
|
being written to a file with other time-averaged values for purposes
|
|
of creating well-formatted output.</p>
|
|
<p>The <em>file</em> keyword allows a filename to be specified. Every <em>Nfreq</em>
|
|
steps, one quantity or vector of quantities is written to the file for
|
|
each input value specified in the fix ave/time command. For <em>mode</em> =
|
|
scalar, this means a single line is written each time output is
|
|
performed. Thus the file ends up to be a series of lines, i.e. one
|
|
column of numbers for each input value. For <em>mode</em> = vector, an array
|
|
of numbers is written each time output is performed. The number of
|
|
rows is the length of the input vectors, and the number of columns is
|
|
the number of values. Thus the file ends up to be a series of these
|
|
array sections.</p>
|
|
<p>The <em>overwrite</em> keyword will continuously overwrite the output file
|
|
with the latest output, so that it only contains one timestep worth of
|
|
output. This option can only be used with the <em>ave running</em> setting.</p>
|
|
<p>The <em>format</em> keyword sets the numeric format of each value when it is
|
|
printed to a file via the <em>file</em> keyword. Note that all values are
|
|
floating point quantities. The default format is %g. You can specify
|
|
a higher precision if desired, e.g. %20.16g.</p>
|
|
<p>The <em>title1</em> and <em>title2</em> and <em>title3</em> keywords allow specification of
|
|
the strings that will be printed as the first 2 or 3 lines of the
|
|
output file, assuming the <em>file</em> keyword was used. LAMMPS uses
|
|
default values for each of these, so they do not need to be specified.</p>
|
|
<p>By default, these header lines are as follows for <em>mode</em> = scalar:</p>
|
|
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="c1"># Time-averaged data for fix ID</span>
|
|
<span class="c1"># TimeStep value1 value2 ...</span>
|
|
</pre></div>
|
|
</div>
|
|
<p>In the first line, ID is replaced with the fix-ID. In the second line
|
|
the values are replaced with the appropriate fields from the fix
|
|
ave/time command. There is no third line in the header of the file,
|
|
so the <em>title3</em> setting is ignored when <em>mode</em> = scalar.</p>
|
|
<p>By default, these header lines are as follows for <em>mode</em> = vector:</p>
|
|
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="c1"># Time-averaged data for fix ID</span>
|
|
<span class="c1"># TimeStep Number-of-rows</span>
|
|
<span class="c1"># Row value1 value2 ...</span>
|
|
</pre></div>
|
|
</div>
|
|
<p>In the first line, ID is replaced with the fix-ID. The second line
|
|
describes the two values that are printed at the first of each section
|
|
of output. In the third line the values are replaced with the
|
|
appropriate fields from the fix ave/time command.</p>
|
|
</div>
|
|
<hr class="docutils" />
|
|
<div class="section" id="restart-fix-modify-output-run-start-stop-minimize-info">
|
|
<h2>Restart, fix_modify, output, run start/stop, minimize info</h2>
|
|
<p>No information about this fix is written to <a class="reference internal" href="restart.html"><span class="doc">binary restart files</span></a>. None of the <a class="reference internal" href="fix_modify.html"><span class="doc">fix_modify</span></a> options
|
|
are relevant to this fix.</p>
|
|
<p>This fix produces a global scalar or global vector or global array
|
|
which can be accessed by various <a class="reference internal" href="Section_howto.html#howto-15"><span class="std std-ref">output commands</span></a>. The values can only be
|
|
accessed on timesteps that are multiples of <em>Nfreq</em> since that is when
|
|
averaging is performed.</p>
|
|
<p>A scalar is produced if only a single input value is averaged and
|
|
<em>mode</em> = scalar. A vector is produced if multiple input values are
|
|
averaged for <em>mode</em> = scalar, or a single input value for <em>mode</em> =
|
|
vector. In the first case, the length of the vector is the number of
|
|
inputs. In the second case, the length of the vector is the same as
|
|
the length of the input vector. An array is produced if multiple
|
|
input values are averaged and <em>mode</em> = vector. The global array has #
|
|
of rows = length of the input vectors and # of columns = number of
|
|
inputs.</p>
|
|
<p>If the fix prouduces a scalar or vector, then the scalar and each
|
|
element of the vector can be either “intensive” or “extensive”,
|
|
depending on whether the values contributing to the scalar or vector
|
|
element are “intensive” or “extensive”. If the fix produces an array,
|
|
then all elements in the array must be the same, either “intensive” or
|
|
“extensive”. If a compute or fix provides the value being time
|
|
averaged, then the compute or fix determines whether the value is
|
|
intensive or extensive; see the doc page for that compute or fix for
|
|
further info. Values produced by a variable are treated as intensive.</p>
|
|
<p>No parameter of this fix can be used with the <em>start/stop</em> keywords of
|
|
the <a class="reference internal" href="run.html"><span class="doc">run</span></a> command. This fix is not invoked during <a class="reference internal" href="minimize.html"><span class="doc">energy minimization</span></a>.</p>
|
|
</div>
|
|
<div class="section" id="restrictions">
|
|
<h2>Restrictions</h2>
|
|
<blockquote>
|
|
<div>none</div></blockquote>
|
|
</div>
|
|
<div class="section" id="related-commands">
|
|
<h2>Related commands</h2>
|
|
<p><a class="reference internal" href="compute.html"><span class="doc">compute</span></a>, <a class="reference internal" href="fix_ave_atom.html"><span class="doc">fix ave/atom</span></a>, <a class="reference internal" href="fix_ave_chunk.html"><span class="doc">fix ave/chunk</span></a>, <a class="reference internal" href="fix_ave_histo.html"><span class="doc">fix ave/histo</span></a>,
|
|
<a class="reference internal" href="variable.html"><span class="doc">variable</span></a>, <a class="reference internal" href="fix_ave_correlate.html"><span class="doc">fix ave/correlate</span></a>,</p>
|
|
</div>
|
|
<div class="section" id="default">
|
|
<h2>Default</h2>
|
|
<p>The option defaults are mode = scalar, ave = one, start = 0, no file
|
|
output, format = %g, title 1,2,3 = strings as described above, and no
|
|
off settings for any input values.</p>
|
|
</div>
|
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</div>
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