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<li class="breadcrumb-item active"><span class="section-number">1.1.4. </span>Per-atom properties</li>
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<p><span class="math notranslate nohighlight">\(\renewcommand{\AA}{\text{Å}}\)</span></p>
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<section id="per-atom-properties">
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<h1><span class="section-number">1.1.4. </span>Per-atom properties<a class="headerlink" href="#per-atom-properties" title="Link to this heading"></a></h1>
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<p>This section documents the following functions:</p>
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<ul class="simple">
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<li><p><a class="reference internal" href="#_CPPv428lammps_extract_atom_datatypePvPKc" title="lammps_extract_atom_datatype"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">lammps_extract_atom_datatype()</span></code></a></p></li>
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<li><p><a class="reference internal" href="#_CPPv424lammps_extract_atom_sizePvPKci" title="lammps_extract_atom_size"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">lammps_extract_atom_size()</span></code></a></p></li>
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<li><p><a class="reference internal" href="#_CPPv419lammps_extract_atomPvPKc" title="lammps_extract_atom"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">lammps_extract_atom()</span></code></a></p></li>
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</ul>
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<hr class="docutils" />
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<dl class="cpp function">
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<dt class="sig sig-object cpp" id="_CPPv428lammps_extract_atom_datatypePvPKc">
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<span id="_CPPv328lammps_extract_atom_datatypePvPKc"></span><span id="_CPPv228lammps_extract_atom_datatypePvPKc"></span><span id="lammps_extract_atom_datatype__voidP.cCP"></span><span class="target" id="library_8h_1aed36a77c70d91c9497b5eee075d18aab"></span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">lammps_extract_atom_datatype</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n sig-param"><span class="pre">handle</span></span>, <span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n sig-param"><span class="pre">name</span></span><span class="sig-paren">)</span><a class="headerlink" href="#_CPPv428lammps_extract_atom_datatypePvPKc" title="Link to this definition"></a><br /></dt>
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<dd><p>Get data type of a LAMMPS per-atom property</p>
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<p><div class="versionadded">
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<p><span class="versionmodified added">Added in version 18Sep2020.</span></p>
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</div>
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<p>This function returns an integer that encodes the data type of the
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per-atom property with the specified name. See
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<code class="xref cpp cpp-enum docutils literal notranslate"><span class="pre">_LMP_DATATYPE_CONST</span></code> for valid values. Callers of
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<a class="reference internal" href="#_CPPv419lammps_extract_atomPvPKc" title="lammps_extract_atom"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">lammps_extract_atom()</span></code></a> can use this information to decide how
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to cast the <code class="docutils literal notranslate"><span class="pre">void</span> <span class="pre">*</span></code> pointer and access the data. In addition,
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<a class="reference internal" href="#_CPPv424lammps_extract_atom_sizePvPKci" title="lammps_extract_atom_size"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">lammps_extract_atom_size()</span></code></a> can be used to get information
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about the vector or array dimensions.</p>
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</p>
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<dl class="field-list simple">
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<dt class="field-odd">Parameters<span class="colon">:</span></dt>
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<dd class="field-odd"><ul class="simple">
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<li><p><strong>handle</strong> – pointer to a previously created LAMMPS instance </p></li>
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<li><p><strong>name</strong> – string with the name of the extracted property </p></li>
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</ul>
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</dd>
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<dt class="field-even">Returns<span class="colon">:</span></dt>
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<dd class="field-even"><p>integer constant encoding the data type of the property or -1 if not found. </p>
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</dd>
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</dl>
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</dd></dl>
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<hr class="docutils" />
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<dl class="cpp function">
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<dt class="sig sig-object cpp" id="_CPPv424lammps_extract_atom_sizePvPKci">
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<span id="_CPPv324lammps_extract_atom_sizePvPKci"></span><span id="_CPPv224lammps_extract_atom_sizePvPKci"></span><span id="lammps_extract_atom_size__voidP.cCP.i"></span><span class="target" id="library_8h_1a2e1f204c0e8b8fc3bde330e9fe94cff3"></span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">lammps_extract_atom_size</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n sig-param"><span class="pre">handle</span></span>, <span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n sig-param"><span class="pre">name</span></span>, <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n sig-param"><span class="pre">type</span></span><span class="sig-paren">)</span><a class="headerlink" href="#_CPPv424lammps_extract_atom_sizePvPKci" title="Link to this definition"></a><br /></dt>
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<dd><p>Get dimension info of a LAMMPS per-atom property</p>
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<p><div class="versionadded">
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<p><span class="versionmodified added">Added in version 19Nov2024.</span></p>
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</div>
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<p>This function returns an integer with the size of the per-atom
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property with the specified name. This allows to accurately determine
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the size of the per-atom data vectors or arrays. For per-atom arrays,
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the <em>type</em> argument is required to return either the number of rows or the
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number of columns. It is ignored for per-atom vectors.</p>
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<p>Callers of <a class="reference internal" href="#_CPPv419lammps_extract_atomPvPKc" title="lammps_extract_atom"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">lammps_extract_atom()</span></code></a> can use this information in
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combination with the result from <a class="reference internal" href="#_CPPv428lammps_extract_atom_datatypePvPKc" title="lammps_extract_atom_datatype"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">lammps_extract_atom_datatype()</span></code></a>
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to decide how to cast the <code class="docutils literal notranslate"><span class="pre">void</span> <span class="pre">*</span></code> pointer and access the data.</p>
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</p>
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<dl class="field-list simple">
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<dt class="field-odd">Parameters<span class="colon">:</span></dt>
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<dd class="field-odd"><ul class="simple">
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<li><p><strong>handle</strong> – pointer to a previously created LAMMPS instance </p></li>
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<li><p><strong>name</strong> – string with the name of the extracted property </p></li>
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<li><p><strong>type</strong> – either LMP_SIZE_ROWS or LMP_SIZE_COLS if <em>name</em> refers to a per-atom array otherwise ignored </p></li>
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</ul>
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</dd>
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<dt class="field-even">Returns<span class="colon">:</span></dt>
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<dd class="field-even"><p>integer with the size of the vector or array dimension or -1 </p>
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</dd>
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</dl>
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</dd></dl>
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<hr class="docutils" />
|
||
<dl class="cpp function">
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<dt class="sig sig-object cpp" id="_CPPv419lammps_extract_atomPvPKc">
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||
<span id="_CPPv319lammps_extract_atomPvPKc"></span><span id="_CPPv219lammps_extract_atomPvPKc"></span><span id="lammps_extract_atom__voidP.cCP"></span><span class="target" id="library_8h_1ac7a2b3791b785a29e1cc383dec467819"></span><span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">lammps_extract_atom</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n sig-param"><span class="pre">handle</span></span>, <span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n sig-param"><span class="pre">name</span></span><span class="sig-paren">)</span><a class="headerlink" href="#_CPPv419lammps_extract_atomPvPKc" title="Link to this definition"></a><br /></dt>
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<dd><p>Get pointer to a LAMMPS per-atom property.</p>
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<p><p>This function returns a pointer to the location of per-atom properties (and
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per-atom-type properties in the case of the ‘mass’ keyword). Per-atom data is
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distributed across sub-domains and thus MPI ranks. The returned pointer is cast
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to <code class="docutils literal notranslate"><span class="pre">void</span> <span class="pre">*</span></code> and needs to be cast to a pointer of data type that the entity
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represents. You can use the functions <a class="reference internal" href="#_CPPv428lammps_extract_atom_datatypePvPKc" title="lammps_extract_atom_datatype"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">lammps_extract_atom_datatype()</span></code></a>
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and <a class="reference internal" href="#_CPPv424lammps_extract_atom_sizePvPKci" title="lammps_extract_atom_size"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">lammps_extract_atom_size()</span></code></a> to determine data type, dimensions and
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sizes of the storage pointed to by the returned pointer.</p>
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<p>A table with supported keywords is included in the documentation of the
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<a class="reference internal" href="Classes_atom.html#_CPPv4N9LAMMPS_NS4Atom7extractEPKc" title="LAMMPS_NS::Atom::extract"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">Atom::extract()</span></code></a> function.</p>
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</p>
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<div class="admonition warning">
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<p class="admonition-title">Warning</p>
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<p>The pointers returned by this function are generally not persistent
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since per-atom data may be re-distributed, re-allocated, and
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re-ordered at every re-neighboring operation.</p>
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</div>
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<dl class="field-list simple">
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<dt class="field-odd">Parameters<span class="colon">:</span></dt>
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<dd class="field-odd"><ul class="simple">
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<li><p><strong>handle</strong> – pointer to a previously created LAMMPS instance </p></li>
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<li><p><strong>name</strong> – string with the name of the extracted property </p></li>
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</ul>
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</dd>
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<dt class="field-even">Returns<span class="colon">:</span></dt>
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