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<span id="label-mca"></span><h1><span class="section-number">8. </span>The Modular Component Architecture (MCA)<a class="headerlink" href="#the-modular-component-architecture-mca" title="Permalink to this heading"></a></h1>
<p>Open MPI is a highly-customizable system; it can be configured via
configuration files, command line parameters, and environment
variables. The main functionality of Open MPI’s configuration system
is through the Modular Component Architecture (MCA).</p>
<ul class="simple">
<li><p>This section describes the MCA itself and how to set MCA parameters at
run time.</p></li>
<li><p>Later sections in this documentation describe different parts of
Open MPI’s functionality, and the specific names and values of MCA
parameters that can be used to affect Open MPI’s behavior.</p></li>
</ul>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p><a class="reference internal" href="launching-apps/pmix-and-prrte.html#label-running-role-of-pmix-and-prte"><span class="std std-ref">The PMIx and PRRTE software packages</span></a> also use the MCA for
their configuration, composition, and run-time tuning.</p>
</div>
<hr class="docutils" />
<div class="section" id="terminology">
<h2><span class="section-number">8.1. </span>Terminology<a class="headerlink" href="#terminology" title="Permalink to this heading"></a></h2>
<p>The Modular Component Architecture (MCA) is the backbone for much of
Open MPI’s functionality. It is a series of <em>projects</em>, <em>frameworks</em>,
<em>components</em>, and <em>modules</em> that are assembled at run-time to create
an MPI implementation.</p>
<p>MCA <em>parameters</em> (also known as MCA <em>variables</em>) are used to customize
Open MPI’s behavior at run-time.</p>
<p>Each of these entities are described below.</p>
<div class="section" id="projects">
<h3><span class="section-number">8.1.1. </span>Projects<a class="headerlink" href="#projects" title="Permalink to this heading"></a></h3>
<p>A <em>project</em> is essentially the highest abstraction layer division in
the Open MPI code base.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>The word “project” is unfortunately overloaded. It can be
used to mean the code/resources/people in the greater Open
MPI community associated with the development of a
particular software package, but it can also be used to mean
a major, top-level section of code within the Open MPI code
base.</p>
<p>For the purposes of this documentation, “project” means the
latter: a major, top-level section of code within the Open
MPI code base.</p>
</div>
<p>The following <em>projects</em> exist in Open MPI v5.0.8:</p>
<ul class="simple">
<li><p><strong>Open Portability Access Layer (OPAL):</strong> Low-level, operating
system and architecture portability code.</p></li>
<li><p><strong>Open MPI (OMPI):</strong> The MPI API and supporting infrastructure.</p></li>
<li><p><strong>OpenSHMEM (OSHMEM):</strong> The OpenSHMEM API and supporting
infrastructure.</p></li>
</ul>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Prior versions of Open MPI also included an Open MPI
Runtime Environment (ORTE) project. ORTE essentially
evolved into the standalone <a class="reference external" href="https://github.com/openpmix/prrte">PMIx Runtime Reference
Environment (PRRTE)</a>
and is now considered a 3rd-party dependency of Open MPI
— not one of its included projects.</p>
<p>See <a class="reference internal" href="launching-apps/pmix-and-prrte.html#label-running-role-of-pmix-and-prte"><span class="std std-ref">the role of PMIx and PRRTE</span></a> for more information.</p>
</div>
</div>
<div class="section" id="frameworks">
<span id="label-mca-frameworks"></span><h3><span class="section-number">8.1.2. </span>Frameworks<a class="headerlink" href="#frameworks" title="Permalink to this heading"></a></h3>
<p>An MCA framework manages zero or more components at run-time and is
targeted at a specific task (e.g., providing MPI collective operation
functionality). Although each MCA framework supports only a single
type of component, it may support multiple components of that type.</p>
<p>Some of the more common frameworks that users may want or need to
customize include the following:</p>
<ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">btl</span></code>: Byte Transport Layer; these components are exclusively used
as the underlying transports for the <code class="docutils literal notranslate"><span class="pre">ob1</span></code> PML component.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">coll</span></code>: MPI collective algorithms</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">io</span></code>: MPI I/O</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">mtl</span></code>: MPI Matching Transport Layer (MTL); these components are
exclusively used as the underlying transports for the <code class="docutils literal notranslate"><span class="pre">cm</span></code> PML
component.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">pml</span></code>: Point-to-point Messaging Layer (PML). These components are
used to implement MPI point-to-point messaging functionality.</p></li>
</ul>
<p>There are many frameworks within Open MPI; the exact set varies
between different versions of Open MPI. You can use the
<a class="reference internal" href="man-openmpi/man1/ompi_info.1.html#man1-ompi-info"><span class="std std-ref">ompi_info(1)</span></a> command to see the full list of
frameworks that are included in Open MPI v5.0.8.</p>
</div>
<div class="section" id="components">
<span id="label-mca-components"></span><h3><span class="section-number">8.1.3. </span>Components<a class="headerlink" href="#components" title="Permalink to this heading"></a></h3>
<p>An MCA component is an implementation of a framework’s formal
interface. It is a standalone collection of code that can be bundled
into a plugin that can be inserted into the Open MPI code base, either
at run-time and/or compile-time.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Good synonyms for Open MPI’s “component” concept are
“plugin”, or “add-on”.</p>
</div>
<p>The exact set of components varies between different versions of Open
MPI. Open MPI’s code base includes support for many components, but
not all of them may be present or available on your system. You can
use the <a class="reference internal" href="man-openmpi/man1/ompi_info.1.html#man1-ompi-info"><span class="std std-ref">ompi_info(1)</span></a> command to see what
components are included in Open MPI v5.0.8 on your system.</p>
</div>
<div class="section" id="modules">
<span id="label-mca-modules"></span><h3><span class="section-number">8.1.4. </span>Modules<a class="headerlink" href="#modules" title="Permalink to this heading"></a></h3>
<p>An MCA module is an instance of a component (in the C++ sense of the
word “instance”; an MCA component is analogous to a C++ class). For
example, if a node running an Open MPI application has two Ethernet
NICs, the Open MPI application will contain one TCP MPI point-to-point
<em>component</em>, but two TCP point-to-point <em>modules</em>.</p>
</div>
<div class="section" id="parameters-variables">
<h3><span class="section-number">8.1.5. </span>Parameters (variables)<a class="headerlink" href="#parameters-variables" title="Permalink to this heading"></a></h3>
<p>MCA <em>parameters</em> (sometimes called MCA <em>variables</em>) are the basic unit
of run-time tuning for Open MPI. They are simple “key = value” pairs
that are used extensively throughout Open MPI. The general rules of
thumb that the developers use are:</p>
<ol class="arabic simple">
<li><p>Instead of using a constant for an important value, make it an MCA
parameter.</p></li>
<li><p>If a task can be implemented in multiple, user-discernible ways,
implement as many as possible, and use an an MCA parameter to
choose between them at run-time.</p></li>
</ol>
<p>For example, an easy MCA parameter to describe is the boundary between
short and long messages in TCP wire-line transmissions. “Short”
messages are sent eagerly whereas “long” messages use a rendezvous
protocol. The decision point between these two protocols is the
overall size of the message (in bytes). By making this value an MCA
parameter, it can be changed at run-time by the user or system
administrator to use a sensible value for a particular environment or
set of hardware (e.g., a value suitable for 1Gpbs Ethernet is probably
not suitable for 100 Gigabit Ethernet, and may require even a third
different value for 25 Gigabit Ethernet).</p>
<hr class="docutils" />
</div>
</div>
<div class="section" id="setting-mca-parameter-values">
<span id="label-running-setting-mca-param-values"></span><h2><span class="section-number">8.2. </span>Setting MCA parameter values<a class="headerlink" href="#setting-mca-parameter-values" title="Permalink to this heading"></a></h2>
<p>MCA parameters may be set in several different ways.</p>
<div class="tip admonition">
<p class="admonition-title">Rationale</p>
<p>Having multiple methods to set MCA parameters allows, for example,
system administrators to fine-tune the Open MPI installation for
their hardware / environment such that normal users can simply use
the default values (that were set by the system administrators).</p>
<p>HPC environments — and the applications that run on them
— tend to be unique. Providing extensive run-time tuning
capabilities through MCA parameters allows the customization of
Open MPI to each system’s / user’s / application’s particular
needs.</p>
</div>
<p>The following are the different methods to set MCA parameters, listed
in priority order:</p>
<ol class="arabic simple">
<li><p>Command line parameters</p></li>
<li><p>Environment variables</p></li>
<li><p>Tuning MCA parameter files</p></li>
<li><p>Configuration files</p></li>
</ol>
<div class="admonition danger">
<p class="admonition-title">Danger</p>
<p>Due to how the PMIx and PRRTE projects both evolved to
become independent projects from Open MPI (<a class="reference internal" href="launching-apps/pmix-and-prrte.html#label-running-role-of-pmix-and-prte"><span class="std std-ref">see this
section for more detail</span></a>), they both have
their own MCA system for setting MCA parameters.</p>
<p>Hence, all the information about MCA parameters below
<em>also</em> applies to PMIx and PRRTE.</p>
</div>
<div class="section" id="command-line-parameters">
<h3><span class="section-number">8.2.1. </span>Command line parameters<a class="headerlink" href="#command-line-parameters" title="Permalink to this heading"></a></h3>
<p>The highest-precedence method is setting MCA parameters on the command
line. For example:</p>
<div class="highlight-sh notranslate"><div class="highlight"><pre><span></span>shell$<span class="w"> </span>mpirun<span class="w"> </span>--mca<span class="w"> </span>mpi_show_handle_leaks<span class="w"> </span><span class="m">1</span><span class="w"> </span>-np<span class="w"> </span><span class="m">4</span><span class="w"> </span>a.out
</pre></div>
</div>
<p>This sets the MCA parameter <code class="docutils literal notranslate"><span class="pre">mpi_show_handle_leaks</span></code> to the value of
1 before running <code class="docutils literal notranslate"><span class="pre">a.out</span></code> with four processes. In general, the
format used on the command line is <code class="docutils literal notranslate"><span class="pre">--mca</span> <span class="pre"><param_name></span> <span class="pre"><value></span></code>.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>When setting a value that includes spaces, you need to use
quotes to ensure that the shell understands that the
multiple tokens are a single value. For example:</p>
<div class="highlight-sh notranslate"><div class="highlight"><pre><span></span>shell$<span class="w"> </span>mpirun<span class="w"> </span>--mca<span class="w"> </span>param<span class="w"> </span><span class="s2">"value with multiple words"</span><span class="w"> </span>...
</pre></div>
</div>
</div>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>Setting Open MPI MCA parameters via the command line
entails using the <code class="docutils literal notranslate"><span class="pre">--mca</span></code> CLI option. When setting
PMIx- and PRRTE-specific MCA parameters via configuration
files, use a different CLI option:</p>
<table class="docutils align-default">
<colgroup>
<col style="width: 38%" />
<col style="width: 62%" />
</colgroup>
<tbody>
<tr class="row-odd"><td><p>Open MPI</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">--mca</span></code></p></td>
</tr>
<tr class="row-even"><td><p>PMIx</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">--pmixmca</span></code></p></td>
</tr>
<tr class="row-odd"><td><p>PRRTE</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">--prtemca</span></code></p></td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="section" id="environment-variables">
<h3><span class="section-number">8.2.2. </span>Environment variables<a class="headerlink" href="#environment-variables" title="Permalink to this heading"></a></h3>
<p>Next, environment variables are searched. Any environment variable
named <code class="docutils literal notranslate"><span class="pre">OMPI_MCA_<param_name></span></code> will be used. For example, the
following has the same effect as the previous example (for sh-flavored
shells):</p>
<div class="highlight-sh notranslate"><div class="highlight"><pre><span></span>shell$<span class="w"> </span><span class="nb">export</span><span class="w"> </span><span class="nv">OMPI_MCA_mpi_show_handle_leaks</span><span class="o">=</span><span class="m">1</span>
shell$<span class="w"> </span>mpirun<span class="w"> </span>-np<span class="w"> </span><span class="m">4</span><span class="w"> </span>a.out
</pre></div>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Just like with command line values, setting environment
variables to values with multiple words requires shell
quoting, such as:</p>
<div class="highlight-sh notranslate"><div class="highlight"><pre><span></span>shell$<span class="w"> </span><span class="nb">export</span><span class="w"> </span><span class="nv">OMPI_MCA_param</span><span class="o">=</span><span class="s2">"value with multiple words"</span>
</pre></div>
</div>
</div>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>Setting Open MPI MCA parameters via environment variables
entails prefixing the parameter name with <code class="docutils literal notranslate"><span class="pre">OMPI_MCA_</span></code>.
When setting PMIx- and PRRTE-specific MCA parameters via
environment variables, use a different prefix:</p>
<table class="docutils align-default">
<colgroup>
<col style="width: 38%" />
<col style="width: 62%" />
</colgroup>
<tbody>
<tr class="row-odd"><td><p>Open MPI</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">OMPI_MCA_</span></code></p></td>
</tr>
<tr class="row-even"><td><p>PMIx</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">PMIX_MCA_</span></code></p></td>
</tr>
<tr class="row-odd"><td><p>PRRTE</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">PRRTE_MCA_</span></code></p></td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="section" id="tuning-mca-parameter-files">
<h3><span class="section-number">8.2.3. </span>Tuning MCA parameter files<a class="headerlink" href="#tuning-mca-parameter-files" title="Permalink to this heading"></a></h3>
<div class="admonition error">
<p class="admonition-title">Error</p>
<p>TODO This entire section needs to be checked for correctness.</p>
</div>
<p>Simple text files can be used to set MCA parameter values for a
specific application.</p>
<p>The <code class="docutils literal notranslate"><span class="pre">mpirun</span> <span class="pre">--tune</span></code> CLI option allows users to specify both MCA
parameters and environment variables from within a single file.</p>
<p>MCA parameters set in tuned parameter files will override any MCA
parameters supplied in global parameter files (e.g.,
<code class="docutils literal notranslate"><span class="pre">$HOME/.openmpi/mca-params.conf</span></code>), but not command line or
environment parameters.</p>
<p>Consider a tuned parameter file name <code class="docutils literal notranslate"><span class="pre">foo.conf</span></code> that is placed in
the same directory as the application <code class="docutils literal notranslate"><span class="pre">a.out</span></code>. A user will typically
run the application as:</p>
<div class="highlight-sh notranslate"><div class="highlight"><pre><span></span>shell$<span class="w"> </span>mpirun<span class="w"> </span>-np<span class="w"> </span><span class="m">2</span><span class="w"> </span>a.out
</pre></div>
</div>
<p>To use the <code class="docutils literal notranslate"><span class="pre">foo.conf</span></code> tuned parameter file, this command line
changes to:</p>
<div class="highlight-sh notranslate"><div class="highlight"><pre><span></span>shell$<span class="w"> </span>mpirun<span class="w"> </span>-np<span class="w"> </span><span class="m">2</span><span class="w"> </span>--tune<span class="w"> </span>foo.conf<span class="w"> </span>a.out
</pre></div>
</div>
<p>Tuned parameter files can be coupled if more than one file is to be
used. If there is another tuned parameter file called <code class="docutils literal notranslate"><span class="pre">bar.conf</span></code>, it
can be added to the command line as follows:</p>
<div class="highlight-sh notranslate"><div class="highlight"><pre><span></span>shell$<span class="w"> </span>mpirun<span class="w"> </span>-np<span class="w"> </span><span class="m">2</span><span class="w"> </span>--tune<span class="w"> </span>foo.conf,bar.conf<span class="w"> </span>a.out
</pre></div>
</div>
<p>The contents of tuned files consist of one or more lines, each of
which contain zero or more <cite>-x</cite> and <cite>–mca</cite> options. Comments are not
allowed. For example, the following tuned file:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>-x envvar1=value1 -mca param1 value1 -x envvar2
-mca param2 value2
-x envvar3
</pre></div>
</div>
<p>is equivalent to:</p>
<div class="highlight-sh notranslate"><div class="highlight"><pre><span></span>shell$<span class="w"> </span>mpirun<span class="w"> </span><span class="se">\</span>
<span class="w"> </span>-x<span class="w"> </span><span class="nv">envvar1</span><span class="o">=</span>value1<span class="w"> </span>-mca<span class="w"> </span>param1<span class="w"> </span>value1<span class="w"> </span>-x<span class="w"> </span>envvar2<span class="w"> </span><span class="se">\</span>
<span class="w"> </span>-mca<span class="w"> </span>param2<span class="w"> </span>value2
<span class="w"> </span>-x<span class="w"> </span>envvar3<span class="w"> </span><span class="se">\</span>
<span class="w"> </span>...rest<span class="w"> </span>of<span class="w"> </span>mpirun<span class="w"> </span><span class="nb">command</span><span class="w"> </span>line...
</pre></div>
</div>
<p>Although the typical use case for tuned parameter files is to be
specified on the command line, they can also be set as MCA parameters
in the environment. The MCA parameter <code class="docutils literal notranslate"><span class="pre">mca_base_envvar_file_prefix</span></code>
contains a comma-delimited list of tuned parameter files exactly as
they would be passed to the <code class="docutils literal notranslate"><span class="pre">--tune</span></code> command line option. The MCA
parameter <code class="docutils literal notranslate"><span class="pre">mca_base_envvar_file_path</span></code> specifies the path to search
for tuned files with relative paths.</p>
<div class="admonition error">
<p class="admonition-title">Error</p>
<p>TODO Check that these MCA var names ^^ are correct.</p>
</div>
</div>
<div class="section" id="configuration-files">
<h3><span class="section-number">8.2.4. </span>Configuration files<a class="headerlink" href="#configuration-files" title="Permalink to this heading"></a></h3>
<p>Finally, simple configuration text files can be used to set MCA
parameter values. Parameters are set one per line (comments are
permitted). For example:</p>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># This is a comment</span>
<span class="c1"># Set the same MCA parameter as in previous examples</span>
<span class="na">mpi_show_handle_leaks</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">1</span>
</pre></div>
</div>
<p>Note that quotes are <em>not</em> necessary for setting multi-word values
in MCA parameter files. Indeed, if you use quotes in the MCA
parameter file, they will be used as part of the value itself. For
example:</p>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># The following two values are different:</span>
<span class="na">param1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">value with multiple words</span>
<span class="na">param2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">"value with multiple words"</span>
</pre></div>
</div>
<p>By default, two files are searched (in order):</p>
<ol class="arabic simple">
<li><p><code class="docutils literal notranslate"><span class="pre">$HOME/.openmpi/mca-params.conf</span></code>: The user-supplied set of
values takes the highest precedence.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">$prefix/etc/openmpi-mca-params.conf</span></code>: The system-supplied set
of values has a lower precedence.</p></li>
</ol>
<p>More specifically, the MCA parameter <code class="docutils literal notranslate"><span class="pre">mca_param_files</span></code> specifies a
colon-delimited path of files to search for MCA parameters. Files to
the left have lower precedence; files to the right are higher
precedence.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Keep in mind that, just like components, these parameter
files are <em>only</em> relevant where they are “visible”
(<a class="reference internal" href="installing-open-mpi/custom-components.html#installing-custom-components-label"><span class="std std-ref">see this FAQ entry</span></a>). Specifically,
Open MPI does not read all the values from these files
during startup and then send them to all nodes in the job.
Instead, the files are read on each node during each
process’ startup.</p>
<p><em>This is intended behavior:</em> it allows for per-node
customization, which is especially relevant in heterogeneous
environments.</p>
</div>
<div class="admonition error">
<p class="admonition-title">Error</p>
<p>TODO This table needs to be checked for correctness.</p>
</div>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>Setting Open MPI MCA parameters via configuration files
entails editing (by default) the <code class="docutils literal notranslate"><span class="pre">mca-params.conf</span></code> or
<code class="docutils literal notranslate"><span class="pre">openmpi-mca-params.conf</span></code> files. When setting PMIx-
and PRRTE-specific MCA parameters via configuration
files, set them (by default) in different files:</p>
<table class="docutils align-default">
<colgroup>
<col style="width: 19%" />
<col style="width: 81%" />
</colgroup>
<tbody>
<tr class="row-odd"><td><p>Open MPI</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">$HOME/.openmpi/mca-params.conf</span></code> or
<code class="docutils literal notranslate"><span class="pre">$prefix/etc/openmpi-mca-params.conf</span></code></p></td>
</tr>
<tr class="row-even"><td><p>PMIx</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">$HOME/.pmix/mca-params.conf</span></code> or
<code class="docutils literal notranslate"><span class="pre">$prefix/etc/openpmix-mca-params.conf</span></code></p></td>
</tr>
<tr class="row-odd"><td><p>PRRTE</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">$HOME/.prrte/mca-params.conf</span></code> or
<code class="docutils literal notranslate"><span class="pre">$prefix/etc/prte-mca-params.conf</span></code></p></td>
</tr>
</tbody>
</table>
</div>
<hr class="docutils" />
</div>
</div>
<div class="section" id="displaying-mca-parameter-values">
<span id="label-running-displaying-mca-param-values"></span><h2><span class="section-number">8.3. </span>Displaying MCA parameter values<a class="headerlink" href="#displaying-mca-parameter-values" title="Permalink to this heading"></a></h2>
<p>MCA parameters are the “life’s blood” of Open MPI. MCA parameters are
used to control both detailed and large-scale behavior of Open MPI and
are present throughout the code base.</p>
<p>This raises an important question: since MCA parameters can be set from a
file, the environment, the command line, and even internally within Open MPI,
how do I actually know what MCA params my job is seeing, and their value?</p>
<p>One way, of course, is to use the <a class="reference internal" href="man-openmpi/man1/ompi_info.1.html#man1-ompi-info"><span class="std std-ref">ompi_info(1)</span></a>
command, which is documented elsewhere (you can use <code class="docutils literal notranslate"><span class="pre">man</span> <span class="pre">ompi_info</span></code>,
or <code class="docutils literal notranslate"><span class="pre">ompi_info</span> <span class="pre">--help</span></code> to get more info on this command). However,
this still doesn’t fully answer the question since <code class="docutils literal notranslate"><span class="pre">ompi_info</span></code> isn’t
an MPI process.</p>
<p>To help relieve this problem, Open MPI provides the MCA parameter
<code class="docutils literal notranslate"><span class="pre">mpi_show_mca_params</span></code> that directs the <code class="docutils literal notranslate"><span class="pre">MPI_COMM_WORLD</span></code> rank 0
process to report the name of MCA parameters, their current value as
seen by that process, and the source that set that value. The
parameter can take several values that define which MCA parameters to
report:</p>
<ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">all</span></code>: report all MCA params. Note that this typically generates a
rather long list of parameters since it includes all of the default
parameters defined inside Open MPI</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">default</span></code>: MCA params that are at their default settings - i.e.,
all MCA params that are at the values set as default within Open MPI</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">file</span></code>: MCA params that had their value set by a file</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">api</span></code>: MCA params set using Open MPI’s internal APIs, perhaps to
override an incompatible set of conditions specified by the user</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">enviro</span></code>: MCA params that obtained their value either from the
local environment or the command line. Open MPI treats environmental
and command line parameters as equivalent, so there currently is no
way to separate these two sources</p></li>
</ul>
<p>These options can be combined in any order by separating them with
commas.</p>
<p>Here is an example of the output generated by this parameter:</p>
<div class="highlight-sh notranslate"><div class="highlight"><pre><span></span>shell$<span class="w"> </span>mpirun<span class="w"> </span>--mca<span class="w"> </span>mpi_show_mca_params<span class="w"> </span>enviro<span class="w"> </span>hello_c
<span class="o">[</span>local-hostname:12345<span class="o">]</span><span class="w"> </span><span class="nv">mpi_show_mca_params</span><span class="o">=</span>enviro<span class="w"> </span><span class="o">(</span>environment<span class="o">)</span>
Hello,<span class="w"> </span>World,<span class="w"> </span>I<span class="w"> </span>am<span class="w"> </span><span class="m">0</span><span class="w"> </span>of<span class="w"> </span><span class="m">1</span>
</pre></div>
</div>
<p>Note that several MCA parameters set by Open MPI itself for internal
uses are displayed in addition to the ones actually set by the user.</p>
<p>Since the output from this option can be long, and since it can be
helpful to have a more permanent record of the MCA parameters used for
a job, a companion MCA parameter <code class="docutils literal notranslate"><span class="pre">mpi_show_mca_params_file</span></code> is
provided. If <code class="docutils literal notranslate"><span class="pre">mpi_show_mca_params_file</span></code> is <em>also</em> set, the output
listing of MCA parameters will be directed into the specified file
instead of being printed to stdout. For example:</p>
<div class="highlight-sh notranslate"><div class="highlight"><pre><span></span>shell$<span class="w"> </span>mpirun<span class="w"> </span>--mca<span class="w"> </span>mpi_show_mca_params<span class="w"> </span>enviro<span class="w"> </span><span class="se">\</span>
<span class="w"> </span>--mca<span class="w"> </span>mpi_show_mca_param_file<span class="w"> </span>/tmp/foo.txt<span class="w"> </span>hello_c
Hello,<span class="w"> </span>World,<span class="w"> </span>I<span class="w"> </span>am<span class="w"> </span><span class="m">0</span><span class="w"> </span>of<span class="w"> </span><span class="m">1</span>
shell$<span class="w"> </span>cat<span class="w"> </span>/tmp/foo.txt
<span class="c1">#</span>
<span class="c1"># This file was automatically generated on Sun Feb 7 14:34:31 2021</span>
<span class="c1"># by MPI_COMM_WORLD rank 0 (out of a total of 16) on savbu-usnic-a</span>
<span class="c1">#</span>
<span class="nv">mpi_show_mca_params</span><span class="o">=</span>enviro<span class="w"> </span><span class="o">(</span>environment<span class="o">)</span>
<span class="nv">mpi_show_mca_params_file</span><span class="o">=</span>/tmp/foo.txt<span class="w"> </span><span class="o">(</span>environment<span class="o">)</span>
</pre></div>
</div>
<hr class="docutils" />
</div>
<div class="section" id="selecting-which-open-mpi-components-are-used-at-run-time">
<span id="label-running-selecting-framework-components"></span><h2><span class="section-number">8.4. </span>Selecting which Open MPI components are used at run time<a class="headerlink" href="#selecting-which-open-mpi-components-are-used-at-run-time" title="Permalink to this heading"></a></h2>
<p>Each MCA framework has a top-level MCA parameter that helps guide
which components are selected to be used at run-time. Specifically,
every framework has an MCA parameter of the same name that can be used
to <em>include</em> or <em>exclude</em> components from a given run.</p>
<p>For example, the <code class="docutils literal notranslate"><span class="pre">btl</span></code> MCA parameter is used to control which BTL
components are used. It takes a comma-delimited list of component
names, and may be optionally prefixed with <code class="docutils literal notranslate"><span class="pre">^</span></code>. For example:</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>The Byte Transfer Layer (BTL) framework is used as the
underlying network transports with the <cite>ob1</cite> Point-to-point
Messaging Layer (PML) component.</p>
</div>
<div class="highlight-sh notranslate"><div class="highlight"><pre><span></span><span class="c1"># Tell Open MPI to include *only* the BTL components listed here and</span>
<span class="c1"># implicitly ignore all the rest:</span>
shell$<span class="w"> </span>mpirun<span class="w"> </span>--mca<span class="w"> </span>btl<span class="w"> </span>self,sm,usnic<span class="w"> </span>...
<span class="c1"># Tell Open MPI to exclude the tcp and uct BTL components</span>
<span class="c1"># and implicitly include all the rest</span>
shell$<span class="w"> </span>mpirun<span class="w"> </span>--mca<span class="w"> </span>btl<span class="w"> </span>^tcp,uct<span class="w"> </span>...
</pre></div>
</div>
<p>Note that <code class="docutils literal notranslate"><span class="pre">^</span></code> can <em>only</em> be the prefix of the <em>entire</em>
comma-delimited list because the inclusive and exclusive behavior are
mutually exclusive. Specifically, since the exclusive behavior means
“use all components <em>except</em> these”, it does not make sense to mix it
with the inclusive behavior of not specifying it (i.e., “use all of
these components”). Hence, something like this:</p>
<div class="highlight-sh notranslate"><div class="highlight"><pre><span></span>shell$<span class="w"> </span>mpirun<span class="w"> </span>--mca<span class="w"> </span>btl<span class="w"> </span>self,sm,usnic,^tcp<span class="w"> </span>...
</pre></div>
</div>
<p>does not make sense — and will cause an error — because it
says “use only the <code class="docutils literal notranslate"><span class="pre">self</span></code>, <code class="docutils literal notranslate"><span class="pre">sm</span></code>, and <code class="docutils literal notranslate"><span class="pre">usnic</span></code> components” but
also “use all components except <code class="docutils literal notranslate"><span class="pre">tcp</span></code>”. These two statements
clearly contradict each other.</p>
<hr class="docutils" />
</div>
<div class="section" id="common-mca-parameters">
<span id="label-mca-common-parameters"></span><h2><span class="section-number">8.5. </span>Common MCA parameters<a class="headerlink" href="#common-mca-parameters" title="Permalink to this heading"></a></h2>
<p>Open MPI has a <em>large</em> number of MCA parameters available. Users can
use the <a class="reference internal" href="man-openmpi/man1/ompi_info.1.html#man1-ompi-info"><span class="std std-ref">ompi_info(1)</span></a> command to see <em>all</em>
available MCA parameters.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Similarly, you can use the <code class="docutils literal notranslate"><span class="pre">pmix_info(1)</span></code> and
<code class="docutils literal notranslate"><span class="pre">prte_info(1)</span></code> commands to see all the MCA parameters
available for the PMIx and PRRTE projects, respectively.</p>
<p>The documentation for these commands are not included in the
Open MPI docs, but they are both quite similar to
<a class="reference internal" href="man-openmpi/man1/ompi_info.1.html#man1-ompi-info"><span class="std std-ref">ompi_info(1)</span></a>.</p>
</div>
<p>The vast majority of these MCA parameters, however, are not useful to
most users. Indeed, there only are a handful of MCA parameters that
are commonly used by end users. <a class="reference internal" href="man-openmpi/man1/ompi_info.1.html#man1-ompi-info-levels"><span class="std std-ref">As described in the
ompi_info(1) man page</span></a>, MCA parameters are
grouped into nine levels, corresponding to the MPI standard’s tool
support verbosity levels. In general:</p>
<ul>
<li><p>Levels 1-3 are intended for the end user.</p>
<ul class="simple">
<li><p>These parameters are generally used to effect whether an Open MPI
job will be able to run correctly.</p></li>
</ul>
<div class="admonition tip">
<p class="admonition-title">Tip</p>
<p>Parameters in levels 1-3 are probably applicable to
most end users.</p>
</div>
</li>
<li><p>Levels 4-6 are intended for the application tuner.</p>
<ul class="simple">
<li><p>These parameters are generally used to tune the performance of an
Open MPI job.</p></li>
</ul>
</li>
<li><p>Levels 7-9 are intended for the MPI implementer.</p>
<ul class="simple">
<li><p>These parameters are esoteric and really only intended for those
who work deep within the implementation of Open MPI code base
itself.</p></li>
</ul>
</li>
</ul>
<p>Although the full list of MCA parameters can be found in the output of
<code class="docutils literal notranslate"><span class="pre">ompi_info(1)</span></code>, the following list of commonly-used parameters is
presented here so that they can easily be found via internet searches:</p>
<ul>
<li><p>Individual framework names are used as MCA parameters to
<a class="reference internal" href="#label-running-selecting-framework-components"><span class="std std-ref">select which components will be used</span></a>. For example, the
<code class="docutils literal notranslate"><span class="pre">btl</span></code> MCA parameter is used to select which components will be
used from the <code class="docutils literal notranslate"><span class="pre">btl</span></code> framework. The <code class="docutils literal notranslate"><span class="pre">coll</span></code> MCA parameter is used
to select which <code class="docutils literal notranslate"><span class="pre">coll</span></code> components are used. And so on.</p></li>
<li><p>Individual framework names with the <code class="docutils literal notranslate"><span class="pre">_base_verbose</span></code> suffix
appended (e.g., <code class="docutils literal notranslate"><span class="pre">btl_base_verbose</span></code>, <code class="docutils literal notranslate"><span class="pre">coll_base_verbose</span></code>, etc.)
can be used to set the general verbosity level of all the components
in that framework.</p>
<ul class="simple">
<li><p>This can be helpful when troubleshooting why certain components
are or are not being selected at run time.</p></li>
</ul>
</li>
<li><p>Many network-related components support “include” and “exclude”
types of components (e.g., <code class="docutils literal notranslate"><span class="pre">btl_tcp_if_include</span></code> and
<code class="docutils literal notranslate"><span class="pre">btl_tcp_if_exclude</span></code>). The “include” parameters specify an
explicit set of network interfaces to use; the “exclude” parameters
specify an explicit set of network interfaces to ignore. Check the
output from <a class="reference internal" href="man-openmpi/man1/ompi_info.1.html#man1-ompi-info"><span class="std std-ref">ompi_info(1)’s</span></a> full list to see
if the network-related component you are using has “include” and
“exclude” network interface parameters.</p>
<div class="admonition important">
<p class="admonition-title">Important</p>
<p>You can only use the “include” <em>or</em> the “exclude”
parameter — they are mutually exclusive from each
other.</p>
</div>
</li>
<li><p><code class="docutils literal notranslate"><span class="pre">mca_base_component_show_load_errors</span></code>: By default, Open MPI
emits a warning message if it fails to open a DSO component at run
time. This typically happens when a shared library that the DSO
requires is not available.</p>
<div class="tip admonition">
<p class="admonition-title">Rationale</p>
<p>In prior versions of Open MPI, components defaulted to building
as DSOs (vs. being included in their parent libraries, such as
<code class="docutils literal notranslate"><span class="pre">libmpi.so</span></code>). On misconfigured systems, sometimes network
acceleration libraries would not be present, meaning that
HPC-class networking components failed to open at run time. As
such, Open MPI would typically fall back to TCP as a network
transport, which usually led to poor performance of end-user
applications.</p>
<p>Having Open MPI warn about such failures to load was useful
because it alerted users to the misconfiguration.</p>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>By default, Open MPI v5.0.8 includes all components in
its base libraries (e.g., on Linux, <code class="docutils literal notranslate"><span class="pre">libmpi.so</span></code> includes
all the components that were built with Open MPI, and
therefore no component need to be opened dynamically), and
does not build its components as DSOs.</p>
<p>This MCA parameter <em>only</em> affects the behavior of when a
component DSO fails to open.</p>
</div>
<p>This MCA parameter can take four general values:</p>
<ol class="arabic">
<li><p><code class="docutils literal notranslate"><span class="pre">yes</span></code> or a boolean “true” value (e.g., <code class="docutils literal notranslate"><span class="pre">1</span></code>): Open MPI will
emit a warning about every component DSO that fails to load.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">no</span></code> or a boolean “false” value (e.g., <code class="docutils literal notranslate"><span class="pre">0</span></code>): Open MPI will
never emit warnings about component DSOs that fail to load.</p></li>
<li><p>A comma-delimited list of frameworks and/or components: Open MPI
will emit a warning about any dynamic component that fails to
open and matches a token in the list. “Match” is defined as:</p>
<ul class="simple">
<li><p>If a token in the list is only a framework name, then any
component in that framework will match.</p></li>
<li><p>If a token in the list specifies both a framework name and a
component name (in the form <code class="docutils literal notranslate"><span class="pre">framework/component</span></code>), then
only the specified component in the specified framework will
match.</p></li>
</ul>
<p>For example, if the value of this MCA parameter is
<code class="docutils literal notranslate"><span class="pre">accelerator,btl/uct</span></code>, then Open MPI warn if any component in
the accelerator framework or if the UCT BTL fails to load at run
time.</p>
</li>
<li><p>The value can also be a <code class="docutils literal notranslate"><span class="pre">^</span></code> character followed by a
comma-delimited list of <code class="docutils literal notranslate"><span class="pre">framework[/component]</span></code> values: This
is similar to the comma-delimited list of tokens, except it will
only emit warnings about dynamic components that fail to load
and do <em>not</em> match a token in the list.</p>
<p>For example, if the value of this MCA parameter is
<code class="docutils literal notranslate"><span class="pre">^accelerator,btl/uct</span></code>, then Open MPI will only warn about the
failure to load DSOs that are neither in the accelerator
framework nor are the UCT BTL.</p>
</li>
</ol>
</li>
</ul>
</div>
<div class="section" id="mca-parameter-changes-between-open-mpi-4-x-and-5-x">
<span id="label-mca-backward-compat"></span><h2><span class="section-number">8.6. </span>MCA Parameter Changes Between Open MPI 4.x and 5.x<a class="headerlink" href="#mca-parameter-changes-between-open-mpi-4-x-and-5-x" title="Permalink to this heading"></a></h2>
<p>When Open MPI <a class="reference internal" href="launching-apps/pmix-and-prrte.html#label-running-role-of-pmix-and-prte"><span class="std std-ref">switched from using ORTE to PRRTE as its run-time
environment,</span></a> some MCA
parameters were renamed to be more consistent and/or allow more
flexible behavior. The deprecated Open MPI MCA parameters listed
below are currently replaced by a corresponding new PRRTE parameter,
but may be removed in future releases.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>In all cases listed below, the deprecated MCA parameter is
an Open MPI MCA parameter, meaning that its corresponding
environment variable was prefixed with <code class="docutils literal notranslate"><span class="pre">OMPI_MCA_</span></code> (e.g.,
<code class="docutils literal notranslate"><span class="pre">OMPI_MCA_orte_xml_output</span></code>). However, the corresponding
new MCA parameter is a PRRTE MCA parameter, meaning that its
corresponding environment variable is prefixed with
<code class="docutils literal notranslate"><span class="pre">PRTE_MCA_</span></code> (e.g., <code class="docutils literal notranslate"><span class="pre">PRTE_MCA_output</span></code>).</p>
<div class="admonition important">
<p class="admonition-title">Important</p>
<p>Yes, that’s a single <code class="docutils literal notranslate"><span class="pre">R</span></code> in the
<code class="docutils literal notranslate"><span class="pre">PRTE_MCA_</span></code> environment variable prefix.
<a class="reference external" href="https://docs.prrte.org/">See this explanation</a> for the when one
R or two R’s are used in the PRRTE name.</p>
</div>
</div>
<table class="docutils align-default">
<colgroup>
<col style="width: 33%" />
<col style="width: 33%" />
<col style="width: 33%" />
</colgroup>
<thead>
<tr class="row-odd"><th class="head"><p>Behavior</p></th>
<th class="head"><p>Deprecated MCA parameter</p></th>
<th class="head"><p>Replaced with</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p>Control buffering of stream output</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">orte_ess_base_stream_buffering</span></code></p>
<p>Values: 0 | 1 | 2</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">ompi_stream_buffering</span></code></p>
<p>Values: same</p>
</td>
</tr>
<tr class="row-odd"><td><p>Output a brief periodic report on launch progress</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">orte_report_launch_progress</span></code></p>
<p>Values: boolean</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">state_base_show_launch_progress</span></code></p>
<p>Values: same</p>
</td>
</tr>
<tr class="row-even"><td><p>Provide all output in XML format</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">orte_xml_output</span></code></p>
<p>Values: boolean</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">output</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">xml</span></code></p>
</td>
</tr>
<tr class="row-odd"><td><p>Tag all output with [job,rank]</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">orte_tag_output</span></code></p>
<p>Values: boolean</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">output</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">tag</span></code></p>
</td>
</tr>
<tr class="row-even"><td><p>Timestamp all application process output</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">orte_timestamp_output</span></code></p>
<p>Values: boolean</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">output</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">timestamp</span></code></p>
</td>
</tr>
<tr class="row-odd"><td><p>Redirect output from application processes into filename / job
/ rank / stdout / stderr / stdddiag.</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">orte_output_filename</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre"><filenname></span></code></p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">output</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">file=<filename></span></code></p>
</td>
</tr>
<tr class="row-even"><td><p>Display a detailed process map just before launch</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_base_display_devel_map</span></code></p>
<p>Values: boolean</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">display</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">map-devel</span></code></p>
</td>
</tr>
<tr class="row-odd"><td><p>Display the topology as part of the process map just before
launch</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_base_display_topo_with_map</span></code></p>
<p>Values: <code class="docutils literal notranslate"><span class="pre"><value></span></code></p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">display</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">topo=<value></span></code></p>
</td>
</tr>
<tr class="row-even"><td><p>Whether to report process bindings to stderr</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">hwloc_base_report_bindings</span></code></p>
<p>Values: boolean</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">display</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">bind</span></code></p>
</td>
</tr>
<tr class="row-odd"><td><p>Display the process map just before launch</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_base_display_map</span></code></p>
<p>Values: boolean</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">display</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">map</span></code></p>
</td>
</tr>
<tr class="row-even"><td><p>Display the allocation being used by this job</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">orte_display_alloc</span></code></p>
<p>Values: boolean</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">display</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">allocation</span></code></p>
</td>
</tr>
<tr class="row-odd"><td><p>Do not run any MPI applications on the local node</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_base_no_schedule_local</span></code></p>
<p>Values: boolean</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_default_mapping_policy</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">[<mapping>]:nolocal</span></code></p>
</td>
</tr>
<tr class="row-even"><td><p>Nodes are allowed to be oversubscribed, even on a managed
system, and overloading of processing elements</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_base_oversubscribe</span></code></p>
<p>Values: boolean</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_default_mapping_policy</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">[<mapping>]:oversubscribe</span></code></p>
</td>
</tr>
<tr class="row-odd"><td><p>Nodes are not to be oversubscribed, even if the system
supports such operation</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_base_no_oversubscribe</span></code></p>
<p>Values: boolean</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_default_mapping_policy</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">[<mapping>]:nooversubscribe</span></code></p>
</td>
</tr>
<tr class="row-even"><td><p>Use hardware threads as independent CPUs</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">hwloc_base_use_hwthreads_as_cpus</span></code></p>
<p>Values: boolean</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_default_mapping_policy</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">[<mapping>]:hwtcpus</span></code></p>
</td>
</tr>
<tr class="row-odd"><td><p>Comma-separated list of ranges specifying logical cpus
allocated to this job</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">hwloc_base_cpu_set</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre"><value></span></code></p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_default_mapping_policy</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">pe-list=<value></span></code></p>
</td>
</tr>
<tr class="row-even"><td><p>List of processor IDs to bind processes to</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">hwloc_base_cpu_list</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre"><value></span></code></p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_default_mapping_policy</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">pe-list=<value></span></code></p>
</td>
</tr>
<tr class="row-odd"><td><p>Bind processes to cores</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">hwloc_base_bind_to_core</span></code></p>
<p>Values: boolean</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">hwloc_default_binding_policy</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">core</span></code></p>
</td>
</tr>
<tr class="row-even"><td><p>Bind processes to sockets</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">hwloc_base_bind_to_socket</span></code></p>
<p>Values: boolean</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">hwloc_default_binding_policy</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">package</span></code></p>
</td>
</tr>
<tr class="row-odd"><td><p>Whether to map and rank processes round-robin by node</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_base_bynode</span></code></p>
<p>Values: boolean</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_default_mapping_policy</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">node</span></code></p>
</td>
</tr>
<tr class="row-even"><td><p>Whether to map and rank processes round-robin by core</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_base_bycore</span></code></p>
<p>Values: boolean</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_default_mapping_policy</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">core</span></code></p>
</td>
</tr>
<tr class="row-odd"><td><p>Whether to map and rank processes round-robin by slot</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_base_byslot</span></code></p>
<p>Values: boolean</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_default_mapping_policy</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">slot</span></code></p>
</td>
</tr>
<tr class="row-even"><td><p>Number of cpus to use for each process</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_base_cpus_per_rank</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre"><X></span></code></p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_default_mapping_policy</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">[<mapping>]:pe=<X></span></code></p>
</td>
</tr>
<tr class="row-odd"><td><p>Launch n processes per node on all allocated nodes</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_ppr_n_pernode</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre"><X></span></code></p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_default_mapping_policy</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">ppr:<X>:node</span></code></p>
</td>
</tr>
<tr class="row-even"><td><p>Launch one process per available node</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_ppr_pernode</span></code></p>
<p>Values: boolean</p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_default_mapping_policy</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">ppr:1:node</span></code></p>
</td>
</tr>
<tr class="row-odd"><td><p>Launch n processes per socket on all allocated nodes</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_ppr_n_persocket</span></code></p>
<p>Value: integer <code class="docutils literal notranslate"><span class="pre"><X></span></code></p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_default_mapping_policy</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">ppr:<X>:package</span></code></p>
</td>
</tr>
<tr class="row-even"><td><p>Comma-separated list of number of processes on a given
resource type</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_ppr_pattern</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre"><value></span></code></p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_default_mapping_policy</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">ppr:<value></span></code></p>
</td>
</tr>
<tr class="row-odd"><td><p>Provide a rankfile file</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">orte_rankfile</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre"><filename></span></code></p>
</td>
<td><p><code class="docutils literal notranslate"><span class="pre">rmaps_default_mapping_policy</span></code></p>
<p>Value: <code class="docutils literal notranslate"><span class="pre">rankfile:file=<filename></span></code></p>
</td>
</tr>
</tbody>
</table>
<div class="section" id="examples">
<h3><span class="section-number">8.6.1. </span>Examples<a class="headerlink" href="#examples" title="Permalink to this heading"></a></h3>
<p>Converting many parameters in the table above are straightforward, where an
integer or boolean value is involved, but some of the conversions require
substituting a boolean with a value to the new parameter, or even constructing
a more complicated composite value for the new parameter. Examples of all
of these types of conversions are given below.</p>
<div class="section" id="simple-values-where-only-the-name-of-the-mca-parameter-changed">
<h4><span class="section-number">8.6.1.1. </span>Simple values, where only the name of the MCA parameter changed<a class="headerlink" href="#simple-values-where-only-the-name-of-the-mca-parameter-changed" title="Permalink to this heading"></a></h4>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variable: (integer value)</span>
<span class="na">export OMPI_MCA_orte_ess_base_stream_buffering</span><span class="o">=</span><span class="s">2</span>
<span class="c1"># New environment variable: (integer value)</span>
<span class="na">export PRTE_MCA_ompi_stream_buffering</span><span class="o">=</span><span class="s">2</span>
</pre></div>
</div>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variable: (boolean value)</span>
<span class="na">export OMPI_MCA_orte_report_launch_progress</span><span class="o">=</span><span class="s">1</span>
<span class="c1"># New environment variable: (boolean value)</span>
<span class="na">export PRTE_MCA_state_base_show_launch_progress</span><span class="o">=</span><span class="s">1</span>
</pre></div>
</div>
</div>
<div class="section" id="convert-from-boolean-value-to-parameter-for-variable">
<h4><span class="section-number">8.6.1.2. </span>Convert from boolean value to parameter for variable<a class="headerlink" href="#convert-from-boolean-value-to-parameter-for-variable" title="Permalink to this heading"></a></h4>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variable: (boolean value)</span>
<span class="na">export OMPI_MCA_orte_xml_output</span><span class="o">=</span><span class="s">1</span>
<span class="c1"># New environment variable: (parameter value)</span>
<span class="na">export PRTE_MCA_output</span><span class="o">=</span><span class="s">xml</span>
</pre></div>
</div>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variables: (boolean value)</span>
<span class="na">export OMPI_MCA_orte_xml_output</span><span class="o">=</span><span class="s">1</span>
<span class="na">export OMPI_MCA_orte_timestamp_output</span><span class="o">=</span><span class="s">1</span>
<span class="c1"># New environment variable: (parameter value)</span>
<span class="na">export PRTE_MCA_output</span><span class="o">=</span><span class="s">xml,timestamp</span>
</pre></div>
</div>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variable: (boolean value)</span>
<span class="na">export OMPI_MCA_rmaps_base_display_devel_map</span><span class="o">=</span><span class="s">1</span>
<span class="c1"># New environment variable: (parameter value)</span>
<span class="na">export PRTE_MCA_display</span><span class="o">=</span><span class="s">map-devel</span>
</pre></div>
</div>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variables: (boolean value)</span>
<span class="na">export OMPI_MCA_rmaps_base_display_devel_map</span><span class="o">=</span><span class="s">1</span>
<span class="na">export OMPI_MCA_rmaps_base_report_bindings</span><span class="o">=</span><span class="s">1</span>
<span class="c1"># New environment variable: (parameter value)</span>
<span class="na">export PRTE_MCA_display</span><span class="o">=</span><span class="s">map-devel,bind</span>
</pre></div>
</div>
</div>
<div class="section" id="convert-from-string-value-to-parameter-for-variable">
<h4><span class="section-number">8.6.1.3. </span>Convert from string value to parameter for variable<a class="headerlink" href="#convert-from-string-value-to-parameter-for-variable" title="Permalink to this heading"></a></h4>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variable: (string value)</span>
<span class="na">export OMPI_MCA_orte_output_filename</span><span class="o">=</span><span class="s">output.txt</span>
<span class="c1"># New environment variable: (parameter value)</span>
<span class="na">export PRTE_MCA_output</span><span class="o">=</span><span class="s">file=output.txt</span>
</pre></div>
</div>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variables: (boolean value)</span>
<span class="na">export OMPI_MCA_orte_xml_output</span><span class="o">=</span><span class="s">1</span>
<span class="na">export OMPI_MCA_orte_timestamp_output</span><span class="o">=</span><span class="s">1</span>
<span class="c1"># Old environment variable: (string value)</span>
<span class="na">export OMPI_MCA_orte_output_filename</span><span class="o">=</span><span class="s">output.txt</span>
<span class="c1"># New environment variable: (parameter value)</span>
<span class="na">export PRTE_MCA_output</span><span class="o">=</span><span class="s">xml,timestamp,file=output.txt</span>
</pre></div>
</div>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variable: (string value)</span>
<span class="na">export OMPI_MCA_rmaps_base_display_topo_with_map</span><span class="o">=</span><span class="s">node</span>
<span class="c1"># New environment variable: (parameter value)</span>
<span class="na">export PRTE_MCA_display</span><span class="o">=</span><span class="s">topo=node</span>
</pre></div>
</div>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variables: (boolean value)</span>
<span class="na">export OMPI_MCA_rmaps_base_display_devel_map</span><span class="o">=</span><span class="s">1</span>
<span class="na">export OMPI_MCA_rmaps_base_report_bindings</span><span class="o">=</span><span class="s">1</span>
<span class="c1"># Old environment variable: (string value)</span>
<span class="na">export OMPI_MCA_rmaps_base_display_topo_with_map</span><span class="o">=</span><span class="s">node</span>
<span class="c1"># New environment variable: (parameter value)</span>
<span class="na">export PRTE_MCA_display</span><span class="o">=</span><span class="s">map-devel,bind,topo=node</span>
</pre></div>
</div>
</div>
<div class="section" id="converting-mapping-parameters">
<h4><span class="section-number">8.6.1.4. </span>Converting mapping parameters<a class="headerlink" href="#converting-mapping-parameters" title="Permalink to this heading"></a></h4>
<p>Mapping parameters were previously prefixed with <code class="docutils literal notranslate"><span class="pre">rmaps_base_</span></code> or <code class="docutils literal notranslate"><span class="pre">hwloc_base_</span></code>
(and also the <code class="docutils literal notranslate"><span class="pre">orte_rankfile</span></code> parameter). These have been updated
to the <code class="docutils literal notranslate"><span class="pre">rmaps_default_mapping_policy</span></code> and <code class="docutils literal notranslate"><span class="pre">hwloc_default_binding_policy</span></code>
parameters to be more consistent and indicate that they are the <em>default</em>
mapping for processes. Some of the old parameters are now values for a
new parameter and some are now suffixes, as shown in the examples below.</p>
<p>The examples below show conversions from old boolean parameters to new
parameter values:</p>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variable: (boolean value)</span>
<span class="na">export OMPI_MCA_rmaps_base_bycore</span><span class="o">=</span><span class="s">1</span>
<span class="c1"># New environment variable: (parameter value)</span>
<span class="na">export PRTE_MCA_rmaps_default_mapping_policy</span><span class="o">=</span><span class="s">core</span>
</pre></div>
</div>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variable: (boolean value)</span>
<span class="na">export OMPI_MCA_hwloc_base_bind_to_socket</span><span class="o">=</span><span class="s">1</span>
<span class="c1"># New environment variable: (parameter value)</span>
<span class="na">export PRTE_MCA_hwloc_default_binding_policy</span><span class="o">=</span><span class="s">package</span>
</pre></div>
</div>
<p>The examples below show conversions from old parameters that have integer or
string values to new parameter values with those same values:</p>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variable: (string value)</span>
<span class="na">export OMPI_MCA_hwloc_base_cpu_set</span><span class="o">=</span><span class="s">1,3,8</span>
<span class="c1"># New environment variable: (parameter value)</span>
<span class="na">export PRTE_MCA_rmaps_default_mapping_policy</span><span class="o">=</span><span class="s">pe-list=1,3,8</span>
</pre></div>
</div>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variable: (integer value)</span>
<span class="na">export OMPI_MCA_rmaps_ppr_n_persocket</span><span class="o">=</span><span class="s">4</span>
<span class="c1"># New environment variable: (parameter value)</span>
<span class="na">export PRTE_MCA_rmaps_default_mapping_policy</span><span class="o">=</span><span class="s">ppr:4:package</span>
</pre></div>
</div>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variable: (string value)</span>
<span class="na">export OMPI_MCA_orte_rankfile</span><span class="o">=</span><span class="s">rankfile.txt</span>
<span class="c1"># New environment variable: (parameter value)</span>
<span class="na">export PRTE_MCA_rmaps_default_mapping_policy</span><span class="o">=</span><span class="s">rankfile:file=rankfile.txt</span>
</pre></div>
</div>
<p>The examples below show conversions from old parameters that map to suffixes
for new parameter values:</p>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variable: (boolean value)</span>
<span class="na">export OMPI_MCA_hwloc_base_use_hwthreads_as_cpus</span><span class="o">=</span><span class="s">1</span>
<span class="c1"># New environment variable: (standalone suffix)</span>
<span class="na">export PRTE_MCA_rmaps_default_mapping_policy</span><span class="o">=</span><span class="s">:hwtcpus</span>
</pre></div>
</div>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variable: (boolean value)</span>
<span class="na">export OMPI_MCA_rmaps_base_oversubscribe</span><span class="o">=</span><span class="s">1</span>
<span class="c1"># New environment variable: (standalone suffix)</span>
<span class="na">export PRTE_MCA_rmaps_default_mapping_policy</span><span class="o">=</span><span class="s">:oversubscribe</span>
</pre></div>
</div>
<p>The examples below show conversions from old parameters that map to suffixes
combined with parameters that have values:</p>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variable: (string value)</span>
<span class="na">export OMPI_MCA_hwloc_base_cpu_set</span><span class="o">=</span><span class="s">1,3,8</span>
<span class="c1"># Old environment variable: (boolean value)</span>
<span class="na">export OMPI_MCA_rmaps_base_oversubscribe</span><span class="o">=</span><span class="s">1</span>
<span class="c1"># New environment variable: (suffix on value)</span>
<span class="na">export PRTE_MCA_rmaps_default_mapping_policy</span><span class="o">=</span><span class="s">pe-list=1,3,8:oversubscribe</span>
</pre></div>
</div>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variable: (integer value)</span>
<span class="na">export OMPI_MCA_rmaps_ppr_n_persocket</span><span class="o">=</span><span class="s">4</span>
<span class="c1"># Old environment variable: (boolean value)</span>
<span class="na">export OMPI_MCA_hwloc_base_use_hwthreads_as_cpus</span><span class="o">=</span><span class="s">1</span>
<span class="c1"># New environment variable: (suffix on value)</span>
<span class="na">export PRTE_MCA_rmaps_default_mapping_policy</span><span class="o">=</span><span class="s">ppr:4:package:hwtcpus</span>
</pre></div>
</div>
<p>Multiple suffixes may be appended to a mapping value:</p>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="c1"># Old environment variable: (integer value)</span>
<span class="na">export OMPI_MCA_rmaps_ppr_n_persocket</span><span class="o">=</span><span class="s">4</span>
<span class="c1"># Old environment variables: (boolean value)</span>
<span class="na">export OMPI_MCA_hwloc_base_use_hwthreads_as_cpus</span><span class="o">=</span><span class="s">1</span>
<span class="na">export OMPI_MCA_rmaps_base_oversubscribe</span><span class="o">=</span><span class="s">1</span>
<span class="c1"># New environment variable: (suffix on value)</span>
<span class="na">export PRTE_MCA_rmaps_default_mapping_policy</span><span class="o">=</span><span class="s">ppr:4:package:hwtcpus:oversubscribe</span>
</pre></div>
</div>
</div>
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