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<div id="projectname">Hardware Locality (hwloc)<span id="projectnumber"> 2.12.2</span>
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<a href="#enum-members">Enumerations</a> |
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<div class="headertitle"><div class="title">Distributing items over a topology</div></div>
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Enumerations</h2></td></tr>
<tr class="memitem:ga8b835295a52b6768a5e6c8abb1f9c54d" id="r_ga8b835295a52b6768a5e6c8abb1f9c54d"><td class="memItemLeft" align="right" valign="top">enum  </td><td class="memItemRight" valign="bottom"><a class="el" href="a00181.html#ga8b835295a52b6768a5e6c8abb1f9c54d">hwloc_distrib_flags_e</a> { <a class="el" href="a00181.html#gga8b835295a52b6768a5e6c8abb1f9c54da2ca08404bfbebe9ed5f34c3d7635425a">HWLOC_DISTRIB_FLAG_REVERSE</a>
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Functions</h2></td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<h2 class="groupheader">Enumeration Type Documentation</h2>
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<h2 class="memtitle"><span class="permalink"><a href="#ga8b835295a52b6768a5e6c8abb1f9c54d">◆ </a></span>hwloc_distrib_flags_e</h2>
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<td class="memname">enum <a class="el" href="a00181.html#ga8b835295a52b6768a5e6c8abb1f9c54d">hwloc_distrib_flags_e</a></td>
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<p>Flags to be given to <a class="el" href="a00181.html#gac14e61485402837e87293079fa0270f2" title="Distribute n items over the topology under roots.">hwloc_distrib()</a>. </p>
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<tr><th colspan="2">Enumerator</th></tr><tr><td class="fieldname"><a id="gga8b835295a52b6768a5e6c8abb1f9c54da2ca08404bfbebe9ed5f34c3d7635425a" name="gga8b835295a52b6768a5e6c8abb1f9c54da2ca08404bfbebe9ed5f34c3d7635425a"></a>HWLOC_DISTRIB_FLAG_REVERSE </td><td class="fielddoc"><p>Distrib in reverse order, starting from the last objects. </p>
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<h2 class="groupheader">Function Documentation</h2>
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<h2 class="memtitle"><span class="permalink"><a href="#gac14e61485402837e87293079fa0270f2">◆ </a></span>hwloc_distrib()</h2>
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<td class="memname">int hwloc_distrib </td>
<td>(</td>
<td class="paramtype"><a class="el" href="a00166.html#ga9d1e76ee15a7dee158b786c30b6a6e38">hwloc_topology_t</a> </td>
<td class="paramname"><em>topology</em>, </td>
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<td class="paramtype"><a class="el" href="a00165.html#ga79b8ab56877ef99ac59b833203391c7d">hwloc_obj_t</a> * </td>
<td class="paramname"><em>roots</em>, </td>
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<td class="paramtype">unsigned </td>
<td class="paramname"><em>n_roots</em>, </td>
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<td class="paramtype"><a class="el" href="a00163.html#ga4bbf39b68b6f568fb92739e7c0ea7801">hwloc_cpuset_t</a> * </td>
<td class="paramname"><em>set</em>, </td>
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<td class="paramtype">unsigned </td>
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<td class="paramtype">int </td>
<td class="paramname"><em>until</em>, </td>
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<td class="paramtype">unsigned long </td>
<td class="paramname"><em>flags</em> </td>
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<p>Distribute <code>n</code> items over the topology under <code>roots</code>. </p>
<p>Array <code>set</code> will be filled with <code>n</code> cpusets recursively distributed linearly over the topology under objects <code>roots</code>, down to depth <code>until</code> (which can be INT_MAX to distribute down to the finest level).</p>
<p><code>n_roots</code> is usually 1 and <code>roots</code> only contains the topology root object so as to distribute over the entire topology.</p>
<p>This is typically useful when an application wants to distribute <code>n</code> threads over a machine, giving each of them as much private cache as possible and keeping them locally in number order.</p>
<p>The caller may typically want to also call <a class="el" href="a00185.html#gaa611a77c092e679246afdf9a60d5db8b" title="Keep a single index among those set in bitmap bitmap.">hwloc_bitmap_singlify()</a> before binding a thread so that it does not move at all.</p>
<p><code>flags</code> should be 0 or a OR'ed set of <a class="el" href="a00181.html#ga8b835295a52b6768a5e6c8abb1f9c54d" title="Flags to be given to hwloc_distrib().">hwloc_distrib_flags_e</a>.</p>
<dl class="section return"><dt>Returns</dt><dd>0 on success, -1 on error.</dd></dl>
<dl class="section note"><dt>Note</dt><dd>On hybrid CPUs (or asymmetric platforms), distribution may be suboptimal since the number of cores or PUs inside packages or below caches may vary (the top-down recursive partitioning ignores these numbers until reaching their levels). Hence it is recommended to distribute only inside a single homogeneous domain. For instance on a CPU with energy-efficient E-cores and high-performance P-cores, one should distribute separately N tasks on E-cores and M tasks on P-cores instead of trying to distribute directly M+N tasks on the entire CPUs.</dd>
<dd>
This function requires the <code>roots</code> objects to have a CPU set. </dd></dl>
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