<html>#1075: Test cases with specific number of processes
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<tr><td style='text-align:right'> Reporter:</td><td>Erik Schnetter</td></tr>
<tr><td style='text-align:right'> Status:</td><td>open</td></tr>
<tr><td style='text-align:right'>Milestone:</td><td></td></tr>
<tr><td style='text-align:right'> Version:</td><td></td></tr>
<tr><td style='text-align:right'> Type:</td><td>enhancement</td></tr>
<tr><td style='text-align:right'> Priority:</td><td>minor</td></tr>
<tr><td style='text-align:right'>Component:</td><td>Cactus</td></tr>
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<p>Comment (by Roland Haas):</p>
<p>The pull request <a data-is-external-link="true" href="https://bitbucket.org/cactuscode/cactus/pull-requests/73/rhaas-lowproctests/diff" rel="nofollow">https://bitbucket.org/cactuscode/cactus/pull-requests/73/rhaas-lowproctests/diff</a> implements the more conservative approach of running all tests requesting up to NPROCS processes. This avoids the issue of oversubscribing, which is indeed an issue on some clusters where asking the queuing system for X cores gets be exactly X cores even if the node I run on (even exclusively) has Y>X cores. It also avoids issues with simfactory’s RunScripts tying the code to cores which will fail if more cores are used than what simfactory thought. </p>
<p>OpenMPI can, and by default on Debian / Ubuntu is, also be configured to disallow oversubscribing a machine, which is an issue already on student laptops with 2 cores for the 4 process tests.</p>
<p>Even undersusbscribing can fail however in cases where mpirun (or its equivalent) is too tightly interwoven with the queuing system and mpirun always starts as many MPI ranks as were requested from the queuing system (and eg SLURM does now how many MPI ranks are used).</p>
<p>There is one further thing to consider: the implementation as proposed (and all older ones as far as I can tell) make it impossible to for example run only the 4 process tests and not the 1 and 2 process tests.</p>
<p>Please review.</p>
<p>--<br/>
Ticket URL: <a href='https://bitbucket.org/einsteintoolkit/tickets/issues/1075/test-cases-with-specific-number-of'>https://bitbucket.org/einsteintoolkit/tickets/issues/1075/test-cases-with-specific-number-of</a></p>
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