The mpitune utility has a predefined range of variable values to be scanned. If you know that your applications use atypical layouts or data sizes, you can overwrite the mpitune defaults to run with a customized set.

Ensure you have write access to the <installdir>/<arch>/<etc> directory.

The mpitune utility uses *.xml files from <installdir>/<arch>/<etc> for its configuration. There are two main configuration files that describe what is tuned and how tuning is performed in the cluster -specific mode: options.xml and Benchmarks/imb.xml, respectively.

For example, if you would like to customize the tuning of the I_MPI_EAGER_THRESHOLD variable, see the bolded text below for appropriate changes.

options.xml:
...
    <option name="I_MPI_EAGER_THRESHOLD" type="global" group="collective" weight="1.0">
        <actions>
            <step order="1" storage="first">
                <additive>
                    <env name="I_MPI_FALLBACK_DEVICE" type="global" value="disable" />
                </additive>
                <range name="range_vars">int_range(8192:524288:*:2)</range> <!-- explicit range from 8k to 512k with power of 2 -->
                <format>@range_vars()</format>
                <result format="[msg_size]" limit="1" separator="" />
            </step>
        </actions>
        <requirements>
        <param name="hosts" value="2:2" /> <!--use 2 hosts -->
      <param name="perhost" value="1:1" /> <!-- with 1 process on host -->
      <param name="processes" value="2:2" /> <!-- and 2 processes total -->
      <param name="devices" value="shm:dapl,shm:tmi" /> <!-- for shim:dapl and shm tmi fabrics (I_MPI_FABRICS) -->
        </requirements>
        <result <!-- internal format description -->
            format="#first#"
            quotes="no"
            quotesInline="no"
        />
    </option>
...
Benchmarks/imb.xml:
    <test title="IMB Sendrecv" weight="1.0">
        <description>Sendrecv test from IMB benchmark for OUTPUT mode</description>
        <executable>"IMB-MPI1" -npmin %proc% -iter 5 -msglen @msglen_file() Sendrecv</executable>
        <function title="msglen_file">range_file(768:1536:+:256;"value[endl]")</function> <!-- msg len file of IMB with range: 768, 1024, 1280 and 1536 bytes -->
        <launch_line>%mpiexec%%globals%%locals%%executable%</launch_line>
        <requirements> <!-- values for requirements section are calculated as intersection with the same block from options.xml file. Results are in the mpitune schedule -->
            <param name="hosts" value="1:-1" />
            <param name="perhost" value="1:-1" />
            <param name="processes" value="2:-1" />
            <param name="devices" value="rdssm,rdma,shm,ssm,sock,shm:dapl,shm:tcp,dapl,tcp,shm,shm:ofa,shm:tmi,ofa,tm i" />
        </requirements>
        <options_filter filter="exclusive"> <!--this section enumerates options to tune by this benchmark-->
            <option type="global"name="I_MPI_EAGER_THRESHOLD" />
            <option type="global"name="I_MPI_INTRANODE_EAGER_THRESHOLD" />
        </options_filter>
        <result <!-- format to parse benchmark output -->
            source="brtime"
            paramGroup="4"
            paramTitle="t[usec]"
            paramTarget="min"
            paramLeftMarginGroup="2"
            paramRightMarginGroup="3"
            paramChooseMode="heaviest"
            paramDiffDelta="0.001"
            msgGroup="0"
            msgTitle="Bytes"
            iterationCompare="min"
            startline=".*(\#bytes\s+\#repetitions).*"
            dataline="\s+(\d+)\s+(\d+)\s+([\d\.]+)\s+([\d\.]+)\s+([\d\.]+)"
            solidatalines="1"
        />
    </test>
...